DESCRIPTION OF SENIOR DEBT SECURITIES

The description below contains summaries of selected provisions of the indenture, including supplemental indentures, under which the senior debt securities (referred to herein as “senior debt securities”) may be issued. These summaries are not complete. The indenture and the form of the supplemental indenture applicable to the senior debt securities have been filed as exhibits to the registration statement. You should read them for provisions that may be important to you. In the summaries below, we have included references to section numbers of the indenture so that you can easily locate these provisions.

We are not required to issue future issues of senior indebtedness under the senior indenture described in this prospectus. We are free to use other indentures or documentation, containing provisions different from those described in this prospectus, in connection with future issues of other senior indebtedness not under this registration statement.

The senior debt securities will be represented either by global senior debt securities registered in the name of The Depository Trust Company, or “DTC,” as depository, or “Depository,” or its nominee, or by securities in certificated form issued to the registered owners, as described in the applicable prospectus supplement. See the information under the heading “Book-Entry System” in this prospectus.

General

The senior debt securities will be issued in one or more new series under an indenture dated as of December 1, 2000 between us and Wells Fargo Bank, National Association, as trustee (the “Senior Debt Trustee”). This indenture, as previously supplemented by supplemental indentures and as may be supplemented by a new supplemental indenture for additional series of debt securities, is referred to in this prospectus as the “Senior Indenture.” As of December 31, 2017, there were seven series of senior debt securities in an aggregate principal amount of $2.9 billion outstanding under the Senior Indenture.

The holders of the outstanding senior debt securities do not, and, unless the supplemental indenture that describes a particular series of senior debt securities provides otherwise with respect to that series, the holders of any senior debt securities offered by this prospectus will not, have the right to require us to repurchase the senior debt securities if we become involved in a highly leveraged or change in control transaction. The Senior Indenture does not have any provision that is designed specifically in response to highly leveraged or change in control transactions.

The senior debt securities will be our unsecured and unsubordinated obligations. The senior debt securities will rank on a parity in right of payment with all of our existing and future unsecured and unsubordinated indebtedness and will rank senior to any of our subordinated indebtedness. As of December 31, 2017, we have no junior subordinated debt outstanding and our aggregate unsecured and unsubordinated indebtedness was approximately $2.9 billion. The senior debt securities will be subordinated to any of our secured indebtedness, as to the assets securing such indebtedness. As of December 31, 2017, we had no secured indebtedness.

In addition, the senior debt securities will be effectively subordinated to all existing and future liabilities of our subsidiaries. We are a holding company and conduct business through our various subsidiaries. As a result, our cash flow and consequent ability to meet our debt obligations primarily depend on the earnings of our subsidiaries, and on dividends and other payments from our subsidiaries. Under certain circumstances, contractual and legal restrictions, as well as the financial condition and operating requirements of our subsidiaries, could limit our ability to obtain cash from our subsidiaries for the purpose of meeting debt service obligations, including the payment of principal and interest on the senior debt securities. Any rights to receive assets of any subsidiary upon its liquidation or reorganization and the consequent right of the holders of the senior debt securities to participate in those assets will be subject to the claims of that subsidiary’s creditors, including trade creditors, except to the extent that we are recognized as a creditor of that subsidiary, in which

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case our claims would still be subordinate to any security interests in the assets of that subsidiary. As of December 31, 2017, our subsidiaries had approximately $27.7 billion of indebtedness and other liabilities outstanding.

The amount of securities that we may issue under the Senior Indenture is not limited. We are not required to issue all senior debt securities of one series at the same time and, unless we indicate otherwise in the applicable prospectus supplement, we may reopen a series for issuances of additional senior debt securities of that series without the consent of the holders of the senior debt securities of that series.

We may also sell hybrid or novel securities now existing or developed in the future that combine certain features of the senior debt securities and other securities described in this prospectus.

When we offer to sell a particular series of senior debt securities, we will describe the specific terms of that series in a prospectus supplement relating to that series, including the following terms:

Any special U.S. federal income tax considerations applicable to senior debt securities sold at an original issue discount and any special U.S. federal income tax or other considerations applicable to any senior debt securities which are denominated in currencies other than U.S. dollars will be described in the prospectus supplement relating to that series of senior debt securities.

Unless we indicate otherwise in the applicable prospectus supplement, the senior debt securities will be denominated in U.S. dollars in minimum denominations of $1,000 and integral multiples thereof.

Registration, Transfer and Exchange

Senior debt securities of any series may be exchanged for other senior debt securities of the same series of any authorized denominations and of a like aggregate principal amount, series and stated maturity and having the same terms and original issue date or dates. (Section 2.6 of the Senior Indenture).

Unless we indicate otherwise in the applicable prospectus supplement, senior debt securities may be presented for registration of transfer (duly endorsed or accompanied by a duly executed written instrument of transfer), at the office of the Senior Debt Trustee maintained for that purpose with respect to any series of senior debt securities and referred to in the applicable prospectus supplement, without service charge and upon payment of any taxes and other governmental charges as described in the Senior Indenture. Any transfer or exchange will be effected if the senior debt securities are duly endorsed by, or accompanied by a written instrument or instruments of transfer in a form satisfactory to the Company and the Senior Debt Trustee and duly executed by the holder of the senior debt security as described in the Senior Indenture. (Section 2.6 of the Senior Indenture).

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The Senior Debt Trustee will not be required to exchange or register a transfer of any senior debt securities of a series selected, called or being called for redemption except, in the case of any senior debt security to be redeemed in part, the portion thereof not to be so redeemed. (Section 2.6 of the Senior Indenture). See the information under the heading “Book-Entry System” in this prospectus.

Payment and Paying Agents

Principal, interest and premium, if any, on senior debt securities issued in the form of global senior debt securities will be paid in the manner described below under the heading “Book-Entry System.” Unless we indicate otherwise in the applicable prospectus supplement, interest on senior debt securities that are in the form of certificated senior debt securities will be paid by check mailed to the holder at that person’s address as it appears in the register for the senior debt securities maintained by the Senior Debt Trustee; however, a holder of $10,000,000 or more senior debt securities having the same interest payment dates will be entitled to receive payments of interest by wire transfer to a bank within the continental United States if appropriate wire transfer instructions have been received by the Senior Debt Trustee on or prior to the applicable record date. (Section 2.12 of the Senior Indenture). Unless we indicate otherwise in the applicable prospectus supplement, the principal, interest at maturity and premium, if any, on senior debt securities in the form of certificated senior debt securities will be payable in immediately available funds at the office of the Senior Debt Trustee. (Section 2.12 of the Senior Indenture).

All monies paid by us to a paying agent for the payment of principal, interest or premium, if any, on any senior debt security which remain unclaimed at the end of two years after that principal, interest or premium has become due and payable will be repaid to us and the holder of that senior debt security will thereafter look only to us for payment of that principal, interest or premium. (Section 4.4 of the Senior Indenture).

Events of Default and Remedies

The following constitute events of default under the Senior Indenture:

(Section 7.1 of the Senior Indenture).

Acceleration of Maturity . If an event of default occurs and is continuing, either the Senior Debt Trustee or the holders of a majority in principal amount of the outstanding senior debt securities may declare the principal amount of all senior debt securities to be due and payable immediately. At any time after an acceleration of the securities has been declared, but before a judgment or decree of the immediate payment of the principal amount of the securities has been obtained, if we pay or deposit with the Senior Debt Trustee a sum sufficient to pay all matured installments of interest and the principal and any premium which has become due otherwise than by acceleration and all defaults have been cured or waived, then that payment or deposit will cause an automatic rescission and annulment of the acceleration of the securities. (Section 7.1 of the Senior Indenture).

Indemnification of Senior Debt Trustee . The Senior Debt Trustee generally will be under no obligation to exercise any of its rights or powers under the Senior Indenture at the request or direction of any of the holders unless such holders have offered reasonable security or indemnity to the Senior Debt Trustee. (Section 8.2 of the Senior Indenture).

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Right to Direct Proceedings . The holders of a majority in principal amount of the outstanding securities generally will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the Senior Debt Trustee, or of exercising any trust or power conferred on the Senior Debt Trustee, relating to the securities. However, the Senior Debt Trustee may refuse to follow any direction that conflicts with law or the Senior Indenture or would expose the Senior Debt Trustee to personal liability or be unduly prejudicial to holders not joining in such proceeding. (Section 7.7 of the Senior Indenture).

Limitation on Rights to Institute Proceedings . No holder of the senior debt securities of a series will have any right to pursue a remedy under the Senior Indenture, unless:

(Section 7.4 of the Senior Indenture).

No Impairment of Right to Receive Payment . Notwithstanding any other provision of the Senior Indenture, the holder of any senior debt security will have the absolute and unconditional right to receive payment of the principal, premium, if any, and interest on that senior debt security when due, and to institute suit for enforcement of that payment. This right may not be impaired without the consent of the holder. (Section 7.4 of the Senior Indenture).

Notice of Default . The Senior Debt Trustee is required to give the holders notice of the occurrence of a default within 90 days of the default, unless the default is cured or waived. Except in the case of a payment default on the senior debt securities, or a default in the payment of any sinking or purchase fund installments, the Senior Debt Trustee may withhold the notice if its board of directors or trustees, executive committee, or a trust committee of directors or trustees or responsible officers determines in good faith that it is in the interest of holders to do so. (Section 7.8 of the Senior Indenture). We are required to deliver to the Senior Debt Trustee each year a certificate as to whether or not we are in compliance with the conditions and covenants under the Senior Indenture. (Section 5.5 of the Senior Indenture).

Modification

Unless we indicate otherwise in the applicable prospectus supplement, we and the Senior Debt Trustee may modify and amend the Senior Indenture from time to time.

We will not need the consent of the holders for the following types of amendments:

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(Section 12.1 of the Senior Indenture).

We will need the consent of the holders of each outstanding security affected by a proposed amendment if the amendment would cause any of the following to occur:

(Section 12.2 of the Senior Indenture).

Amendments other than those described in the above two paragraphs will require the approval of a majority in principal amount of the outstanding securities.

Conversion Rights

Any supplemental indenture establishing a series of senior debt securities may provide for conversion rights. We will describe in the applicable prospectus supplement the particular terms and conditions, if any, on which senior debt securities may be convertible into other securities. These terms will include the conversion rate, the conversion period, provisions as to whether conversion will be mandatory or at our option or the option of the holder, events requiring an adjustment of the conversion rate and provisions affecting conversion in the event of the redemption of the debt securities. If we issue convertible debt securities, we will need to supplement the indenture to add applicable provisions regarding conversion.

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Defeasance and Discharge

We may be discharged from all obligations relating to the senior debt securities and the Senior Indenture (except for specified obligations such as obligations to register the transfer or exchange of securities, replace stolen, lost or mutilated securities and maintain paying agencies) if we irrevocably deposit with the Senior Debt Trustee, in trust for the benefit of holders of securities, money or U.S. government obligations (or any combination thereof) sufficient to make all payments of principal, premium and interest on the securities on the dates those payments are due. To discharge these obligations, we must deliver to the Senior Debt Trustee an opinion of counsel that the holders of the securities will not recognize income, gain or loss for federal income tax purposes as a result of such defeasance or discharge of the Senior Indenture. Upon any discharge of our obligations as described above, we will be deemed to have paid and discharged our entire indebtedness represented by the senior debt securities and our obligations under the senior debt securities. (Section 4.1 of the Senior Indenture).

Consolidation, Merger and Sale of Assets; No Financial Covenants

We will not consolidate with or merge into any other corporation or sell, or otherwise dispose all or substantially all of our assets unless the successor or transferee corporation assumes by supplemental indenture our obligations to pay the principal, interest and premium on all the securities and our obligation to perform every covenant of the Senior Indenture that we are to perform or observe, and we or the successor or transferee corporation, as applicable, are not immediately following such consolidation or merger, or sale, or disposition in default in the performance of any such covenant. Upon any consolidation or merger, or any sale, transfer or other disposition of all or substantially all of our assets, the successor or transferee corporation will succeed to, and be substituted for, and may exercise all of our rights and powers under the Senior Indenture with the same effect as if the successor corporation had been named as us in the Senior Indenture and we will be released from all obligations under the Senior Indenture. Regardless of whether a sale or transfer of assets might otherwise be considered a sale of all or substantially all of our assets, the Senior Indenture also specifically permits any sale, transfer or conveyance of our non-utility subsidiaries if, following such sale or transfer, the securities are rated by Standard & Poor’s Ratings Group and Moody’s Investors Service, Inc. at least as high as the ratings accorded the securities immediately prior to the sale, transfer or disposition. (Sections 11.1 and 11.2 of the Senior Indenture).

The Senior Indenture does not contain any financial or other similar restrictive covenants.

Resignation or Removal of Senior Debt Trustee

The Senior Debt Trustee may resign at any time by notifying us in writing and specifying the day that the resignation is to take effect. The resignation will not take effect, however, until the later of the appointment of a successor trustee and the day the resignation is to take effect. (Section 8.10 of the Senior Indenture).

The holders of a majority in principal amount of the outstanding securities may remove the Senior Debt Trustee at any time. In addition, so long as no event of default or event which, with the giving of notice or lapse of time or both, would become an event of default has occurred and is continuing, we may remove the Senior Debt Trustee upon notice to the holder of each security outstanding and written notice to the Senior Debt Trustee. (Section 8.10 of the Senior Indenture).

Governing Law

The Senior Indenture and the senior debt securities will be governed by, and will be construed in accordance with, the laws of the State of Minnesota.

Concerning the Senior Debt Trustee

Wells Fargo Bank, National Association is the Senior Debt Trustee. We maintain banking relationships with the Senior Debt Trustee in the ordinary course of business. The Senior Debt Trustee also acts as trustee for our junior subordinated debt securities and certain debt securities of our subsidiaries.

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DESCRIPTION OF SUBORDINATED DEBT SECURITIES

We may issue subordinated debt securities (other than the junior subordinated debt securities (as defined below under “Description of Junior Subordinated Debt Securities” in this prospectus)), in one or more series, under one or more subordinated indentures. The description below contains summaries of selected provisions of the indenture under which the subordinated debt securities may be issued. These summaries are not complete. The form of subordinated indenture and the form of the supplemental indenture applicable to the subordinated debt securities have been filed as exhibits to the registration statement. You should read them for provisions that may be important to you. In the summaries below, we have included references to section numbers of the subordinated indenture so that you can easily locate these provisions.

We are not required to issue future issues of subordinated indebtedness under the subordinated indenture described in this prospectus. We are free to use other indentures or documentation, containing provisions different from those described in this prospectus, in connection with future issues of other subordinated indebtedness not under this registration statement.

The subordinated debt securities will be represented either by global subordinated debt securities registered in the name of the Depository or its nominee, or by securities in certificated form issued to the registered owners, as set forth in the applicable prospectus supplement. See the information under the heading “Book-Entry System” in this prospectus.

General

The subordinated debt securities will be issued in one or more new series under a subordinated indenture to be entered into between us and a trustee to be named therein, as trustee (the “Subordinated Trustee”). This subordinated indenture, as it may be supplemented by a supplemental indenture for each series of subordinated debt securities, is referred to in this prospectus as the “Subordinated Indenture.” As of December 31, 2017, we have no subordinated debt securities outstanding under the Subordinated Indenture.

The subordinated debt securities will be our unsecured obligations and will rank senior to any of our junior subordinated indebtedness and will rank junior in right of payment to our Senior Indebtedness, as described under the caption “—Subordination”. As of December 31, 2017, our outstanding Senior Indebtedness (as defined below) was approximately $2.9 billion.

In addition, the subordinated debt securities will be effectively subordinated to all existing and future liabilities of our subsidiaries, including trade creditors, debtholders, secured creditors, taxing authorities, guarantee holders and any preferred stockholders. We are a holding company and conduct business through our various subsidiaries. As a result, our cash flow and consequent ability to meet our debt obligations primarily depend on the earnings of our subsidiaries, and on dividends and other payments from our subsidiaries. Under certain circumstances, contractual and legal restrictions, as well as the financial condition and operating requirements of our subsidiaries, could limit our ability to obtain cash from our subsidiaries for the purpose of meeting debt service obligations, including the payment of principal and interest on the subordinated debt securities. Any rights to receive assets of any subsidiary upon its liquidation or reorganization and the consequent right of the holders of the subordinated debt securities to participate in those assets will be subject to the claims of that subsidiary’s creditors, including trade creditors, except to the extent that we are recognized as a creditor of that subsidiary, in which case our claims would still be subordinate to any security interests in the assets of that subsidiary. As of December 31, 2017, our subsidiaries had approximately $27.7 billion of indebtedness and other liabilities outstanding.

Unless the supplemental indenture that describes a particular series of subordinated debt securities provides otherwise with respect to that series, the holders of any subordinated debt securities offered by this prospectus will not have the right to require us to repurchase the subordinated debt securities if we become involved in a highly leveraged or change in control transaction. The Subordinated Indenture does not have any provision that is designed specifically in response to highly leveraged or change in control transactions.

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The amount of subordinated debt securities that we may issue under the Subordinated Indenture is not limited. We are not required to issue all subordinated debt securities of one series at the same time and, unless we indicate otherwise in the applicable prospectus supplement, we may reopen a series for issuances of additional subordinated debt securities of that series without the consent of the holders of the subordinated debt securities of that series.

We may also sell hybrid or novel securities now existing or developed in the future that combine certain features of the subordinated debt securities and other securities described in this prospectus.

When we offer to sell a particular series of subordinated debt securities, we will describe the specific terms of that series in a prospectus supplement relating to that series, including the following terms:

Any special U.S. federal income tax considerations applicable to subordinated debt securities sold at an original issue discount and any special U.S. federal income tax or other considerations applicable to any subordinated debt securities which are denominated in currencies other than U.S. dollars will be described in the prospectus supplement relating to that series of subordinated debt securities.

Unless we indicate otherwise in the applicable prospectus supplement, the subordinated debt securities will be denominated in U.S. dollars in minimum denominations of $1,000 and integral multiples thereof.

Subordination

Each series of subordinated debt securities will be subordinate and junior in right of payment, to the extent set forth in the Subordinated Indenture, to all Senior Indebtedness (as defined below). If:

then the holders of Senior Indebtedness generally will have the right to receive payment, in the case of the first instance above, of all amounts due or to become due upon that Senior Indebtedness, and, in the case of the second and third instances, of all amounts due on that Senior Indebtedness, or we will make provision for those

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payments, before the holders of any subordinated debt securities have the right to receive any payments of principal or interest on their securities. (Sections 14.1 and 14.9 of the Subordinated Indenture).

Unless we indicate otherwise in the applicable prospectus supplement, “Senior Indebtedness” includes the senior debt securities and means, with respect to any series of subordinated debt securities, the principal, premium, interest and any other payment in respect of any of the following, whether outstanding on the date of execution of the Subordinated Indenture or thereafter incurred, other than obligations expressly on a parity with the subordinated debt securities or junior to the subordinated debt securities:

Senior Indebtedness will not include trade accounts payable, accrued liabilities arising in the ordinary course of business, indebtedness to our subsidiaries or any indebtedness which is by its terms junior to or on parity with the subordinated debt securities, including the junior subordinated indebtedness issued under the Junior Subordinated Indenture. (Section 1.3 of the Subordinated Indenture.)

Senior Indebtedness will be entitled to the benefits of the subordination provisions in the Subordinated Indenture irrespective of the amendment, modification or waiver of any term of the Senior Indebtedness. We may not amend the Subordinated Indenture to change the subordination of any outstanding subordinated debt securities without the consent of each holder of subordinated debt securities that such amendment would adversely affect. (Sections 12.2 and 14.7 of the Subordinated Indenture.)

The Subordinated Indenture does not limit the amount of subordinated debt securities that we may issue.

Registration, Transfer and Exchange

Subordinated debt securities of any series may be exchanged for other subordinated debt securities of the same series of any authorized denominations and of a like aggregate principal amount, series and stated maturity and having the same terms and original issue date or dates. (Section 2.6 of the Subordinated Indenture).

Unless we indicate otherwise in the applicable prospectus supplement, subordinated debt securities may be presented for registration of transfer (duly endorsed or accompanied by a duly executed written instrument of transfer), at the office of the Subordinated Debt Trustee maintained for that purpose with respect to any series of subordinated debt securities and referred to in the applicable prospectus supplement, without service charge and upon payment of any taxes and other governmental charges as described in the Subordinated Indenture. Any transfer or exchange will be effected if the subordinated debt securities are duly endorsed by, or accompanied by a written instrument or instruments of transfer in a form satisfactory to the Company and the Subordinated Debt Trustee and duly executed by the holder of the subordinated debt security as described in the Subordinated Indenture. (Section 2.6 of the Subordinated Indenture).

The Subordinated Debt Trustee will not be required to exchange or register a transfer of any subordinated debt securities of a series selected, called or being called for redemption except, in the case of any subordinated

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debt security to be redeemed in part, the portion thereof not to be so redeemed. (Section 2.6 of the Subordinated Indenture). See the information under the heading “Book-Entry System” in this prospectus.

Payment and Paying Agents

Principal, interest and premium, if any, on subordinated debt securities issued in the form of global subordinated debt securities will be paid in the manner described below under the heading “Book-Entry System.” Unless we indicate otherwise in the applicable prospectus supplement, interest on subordinated debt securities that are in the form of certificated subordinated debt securities will be paid by check mailed to the holder at that person’s address as it appears in the register for the subordinated debt securities maintained by the Subordinated Debt Trustee; however, a holder of $10,000,000 or more subordinated debt securities having the same interest payment dates will be entitled to receive payments of interest by wire transfer to a bank within the continental United States if appropriate wire transfer instructions have been received by the Subordinated Debt Trustee on or prior to the applicable record date. (Section 2.12 of the Subordinated Indenture). Unless we indicate otherwise in the applicable prospectus supplement, the principal, interest at maturity and premium, if any, on subordinated debt securities in the form of certificated subordinated debt securities will be payable in immediately available funds at the office of the Subordinated Debt Trustee. (Section 2.12 of the Subordinated Indenture).

All monies paid by us to a paying agent for the payment of principal, interest or premium, if any, on any subordinated debt security which remain unclaimed at the end of two years after that principal, interest or premium has become due and payable will be repaid to us and the holder of that subordinated debt security will thereafter look only to us for payment of that principal, interest or premium. (Section 4.4 of the Subordinated Indenture).

Events of Default and Remedies

Unless we provide otherwise in a prospectus supplement, the following will constitute events of default under the Subordinated Indenture with respect to the subordinated debt securities of any series:

(Section 7.1 of the Subordinated Indenture).

Acceleration of Maturity . If an event of default occurs and is continuing with respect to a series of subordinated debt securities, either the Subordinated Debt Trustee or the holders of at least 25% in principal amount of the outstanding securities of that series may declare the principal amount of all securities of that series to be due and payable immediately. At any time after an acceleration of a series of securities has been declared, but before a judgment or decree of the immediate payment of the principal amount of those securities has been obtained, if:

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Indemnification of Subordinated Debt Trustee . The Subordinated Debt Trustee generally will be under no obligation to exercise any of its rights or powers under the Subordinated Indenture at the request or direction of any of the holders unless such holders have offered reasonable security or indemnity to the Subordinated Debt Trustee. (Section 8.2 of the Subordinated Indenture).

Right to Direct Proceedings . The holders of a majority in principal amount of the outstanding securities of a series generally will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the Subordinated Debt Trustee, or of exercising any trust or power conferred on the Subordinated Debt Trustee, relating to the securities of that series. Notwithstanding, the Subordinated Debt Trustee may refuse to follow any direction that conflicts with law or the Subordinated Indenture or would expose the Subordinated Debt Trustee to personal liability or be unduly prejudicial to holders not joining in such proceeding. (Section 7.7 of the Subordinated Indenture).

Limitation on Rights to Institute Proceedings . No holder of the subordinated debt securities of a series will have any right to pursue a remedy under the Subordinated Indenture, unless:

(Section 7.4 of the Subordinated Indenture).

No Impairment of Right to Receive Payment . Notwithstanding any other provision of the Subordinated Indenture, the holder of any subordinated debt security will have the absolute and unconditional right to receive payment of the principal, premium, if any, and interest on that subordinated debt security when due and payable, and to institute suit for enforcement of that payment. This right may not be impaired without the consent of the holder. (Section 7.4 of the Subordinated Indenture).

Notice of Default . The Subordinated Debt Trustee is required to give the holders of a series of securities notice of the occurrence of a default within 90 days of the default with respect to that series, unless the default is cured or waived. Except in the case of a payment default on the subordinated debt securities, or a default in the payment of any sinking or purchase fund installments, the Subordinated Debt Trustee may withhold the notice if its board of directors or trustees, executive committee, or a trust committee of directors or trustees or responsible officers determines in good faith that it is in the interest of holders of the series of affected securities to do so. (Section 7.8 of the Subordinated Indenture). We are required to deliver to the Subordinated Debt Trustee each year a certificate as to whether or not we are in compliance with the conditions and covenants under the Subordinated Indenture. (Section 5.5 of the Subordinated Indenture).

Conversion Rights

A series of subordinated debt securities may provide for conversion rights. We will describe in the applicable prospectus supplement the particular terms and conditions, if any, on which subordinated debt securities may be convertible into other securities. These terms will include the conversion rate, the conversion period, provisions as to whether conversion will be mandatory or at our option or the option of the holder, events requiring an adjustment of the conversion rate and provisions affecting conversion in the event of the redemption of the debt securities.

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Defeasance and Discharge

We may be discharged from all obligations relating to the subordinated debt securities and the Subordinated Indenture (except for specified obligations such as obligations to register the transfer or exchange of securities, replace stolen, lost or mutilated securities and maintain paying agencies) if we irrevocably deposit with the Subordinated Debt Trustee, in trust for the benefit of holders of securities, money or U.S. government obligations (or any combination thereof) sufficient to make all payments of principal, premium and interest on the securities on the dates those payments are due. To discharge these obligations, we must deliver to the Subordinated Debt Trustee an opinion of counsel to the effect that we have received from, or there has been published by, the Internal Revenue Service a ruling or similar pronouncement by the Internal Revenue Service or that there has been a change in law, in either case to the effect that the holders of the securities will not recognize income, gain or loss for federal income tax purposes as a result of such defeasance or discharge of the Subordinated Indenture, and holders will be subject to tax in the same manner, in the same amounts and same time as would have been the case absent such defeasance. Upon any discharge of our obligations as described above, we will be deemed to have paid and discharged our entire indebtedness represented by the subordinated debt securities and our obligations under the subordinated debt securities. (Section 4.1 of the Subordinated Indenture).

Modification

Unless we indicate otherwise in the applicable prospectus supplement, we and the Subordinated Debt Trustee may modify and amend the Subordinated Indenture from time to time.

We will not need the consent of the holders for the following types of amendments:

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(Section 12.1 of the Subordinated Indenture).

We will need the consent of the holders of each outstanding security affected by a proposed amendment if the amendment would cause any of the following to occur:

(Section 12.2 of the Subordinated Indenture).

Amendments other than those described in the above two paragraphs will require the approval of a majority in principal amount of the outstanding securities of all series, provided that if there are securities of more than one series outstanding and if a proposed amendment would directly affect the rights of holders of securities of one or more, but less than all, of such series, then the approval of a majority in principal amount of the outstanding securities of all series so directly affected, considered as one class, will be required.

Consolidation, Merger and Sale of Assets; No Financial Covenants

We will not consolidate with or merge into any other corporation or sell, or otherwise dispose all or substantially all of our assets unless the successor or transferee corporation assumes by supplemental indenture our obligations to pay the principal, interest and premium on all the securities and our obligation to perform every covenant of the Subordinated Indenture that we are to perform or observe, and we or the successor or transferee corporation, as applicable, are not immediately following such consolidation or merger, or sale, or disposition in default in the performance of any such covenant. Upon any consolidation or merger, or any sale, transfer or other disposition of all or substantially all of our assets, the successor or transferee corporation will succeed to, and be substituted for, and may exercise all of our rights and powers under the Subordinated Indenture with the same effect as if the successor corporation had been named as us in the Subordinated Indenture and we will be released from all obligations under the Subordinated Indenture. Regardless of whether a sale or transfer of assets might otherwise be considered a sale of all or substantially all of our assets, the Subordinated Indenture also specifically permits any sale, transfer or conveyance of our non-utility subsidiaries if, following such sale or transfer, the securities are rated by Standard & Poor’s Ratings Group and Moody’s Investors Service, Inc. at least as high as the ratings accorded the securities immediately prior to the sale, transfer or disposition. (Sections 11.1 and 11.2 of the Subordinated Indenture).

The Subordinated Indenture does not contain any financial or other similar restrictive covenants.

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Resignation or Removal of Subordinated Debt Trustee

The Subordinated Debt Trustee may resign with respect to securities of any series at any time by notifying us in writing and specifying the day that the resignation is to take effect. The resignation will not take effect, however, until the later of the appointment of a successor trustee and the day the resignation is to take effect. (Section 8.10 of the Subordinated Indenture).

The holders of a majority in principal amount of the outstanding securities of any series may remove the Subordinated Debt Trustee as trustee of that series of securities at any time. In addition, so long as no event of default or event which, with the giving of notice or lapse of time or both, would become an event of default has occurred and is continuing with respect to securities of any series, we may remove the Subordinated Debt Trustee with respect to securities of that series upon notice to the holder of each security of that series outstanding and written notice to the Subordinated Debt Trustee. (Section 8.10 of the Subordinated Indenture).

Governing Law

The Subordinated Indenture and the subordinated debt securities will be governed by, and will be construed in accordance with, the laws of the State of Minnesota. (Section 15.4 of the Subordinated Indenture).

The Subordinated Debt Trustee

The Subordinated Indenture requires that the Subordinated Trustee be a corporation organized and doing business under the laws of the United States or any State thereof or of the District of Columbia (or a corporation or other person permitted to act as trustee by the Commission), subject to supervision or examination by such bodies and authorized under such laws to exercise corporate trust powers and having a combined capital and surplus of at least $150,000,000. If at any time the Subordinated Trustee shall cease to be eligible to serve as trustee under the Subordinated Indenture, the Subordinated Trustee shall resign immediately and a new trustee will be appointed as provided in the Subordinated Indenture.

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DESCRIPTION OF JUNIOR SUBORDINATED DEBT SECURITIES

The description below contains summaries of selected provisions of the indenture, including supplemental indentures, under which the junior subordinated debt securities may be issued (referred to herein as “junior subordinated indenture”). These summaries are not complete. The junior subordinated indenture and the form of the supplemental indenture applicable to the junior subordinated debt securities have been filed as exhibits to the registration statement. You should read them for provisions that may be important to you. In the summaries below, we have included references to section numbers of the junior subordinated indenture so that you can easily locate these provisions.

We are not required to issue future issues of junior subordinated indebtedness under the junior subordinated indenture described in this prospectus. We are free to use other indentures or documentation, containing provisions different from those described in this prospectus, in connection with future issues of other junior subordinated indebtedness not under this registration statement.

The junior subordinated debt securities will be represented either by global junior subordinated debt securities registered in the name of the Depository or its nominee, or by securities in certificated form issued to the registered owners, as set forth in the applicable prospectus supplement. See the information under the heading “Book-Entry System” in this prospectus.

General

The junior subordinated debt securities will be issued in one or more new series under an indenture dated as of January 1, 2008 between us and Wells Fargo Bank, National Association, as trustee (the “Junior Subordinated Debt Trustee”). This junior subordinated indenture, as it may be supplemented by a supplemental indenture for each series of junior subordinated debt securities, is referred to in this prospectus as the “Junior Subordinated Indenture.” As of December 31, 2017, we have no junior subordinated debt outstanding under the Junior Subordinated Indenture.

The junior subordinated debt securities will be our unsecured obligations and will rank on a parity in right of payment with all of our future junior subordinated indebtedness and junior in right of payment to our Senior Ranking Indebtedness, as described under the caption “—Subordination”. As of December 31, 2017, our outstanding Senior Ranking Indebtedness (as defined below) was approximately $2.9 billion.

In addition, the junior subordinated debt securities will be effectively subordinated to all existing and future liabilities of our subsidiaries, including trade creditors, debtholders, secured creditors, taxing authorities, guarantee holders and any preferred stockholders. We are a holding company and conduct business through our various subsidiaries. As a result, our cash flow and consequent ability to meet our debt obligations primarily depend on the earnings of our subsidiaries, and on dividends and other payments from our subsidiaries. Under certain circumstances, contractual and legal restrictions, as well as the financial condition and operating requirements of our subsidiaries, could limit our ability to obtain cash from our subsidiaries for the purpose of meeting debt service obligations, including the payment of principal and interest on the junior subordinated debt securities. Any rights to receive assets of any subsidiary upon its liquidation or reorganization and the consequent right of the holders of the junior subordinated debt securities to participate in those assets will be subject to the claims of that subsidiary’s creditors, including trade creditors, except to the extent that we are recognized as a creditor of that subsidiary, in which case our claims would still be subordinate to any security interests in the assets of that subsidiary. As of December 31, 2017, our subsidiaries had approximately $27.7 billion of indebtedness and other liabilities outstanding.

Unless the supplemental indenture that describes a particular series of junior subordinated debt securities provides otherwise with respect to that series, the holders of any junior subordinated debt securities offered by this prospectus will not have the right to require us to repurchase the junior subordinated debt securities if we

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become involved in a highly leveraged or change in control transaction. The Junior Subordinated Indenture does not have any provision that is designed specifically in response to highly leveraged or change in control transactions.

The amount of junior subordinated debt securities that we may issue under the Junior Subordinated Indenture is not limited. We are not required to issue all junior subordinated debt securities of one series at the same time and, unless we indicate otherwise in the applicable prospectus supplement, we may reopen a series for issuances of additional junior subordinated debt securities of that series without the consent of the holders of the junior subordinated debt securities of that series.

We may also sell hybrid or novel securities now existing or developed in the future that combine certain features of the junior subordinated debt securities and other securities described in this prospectus.

When we offer to sell a particular series of junior subordinated debt securities, we will describe the specific terms of that series in a prospectus supplement relating to that series, including the following terms:

Any special U.S. federal income tax considerations applicable to junior subordinated debt securities sold at an original issue discount and any special U.S. federal income tax or other considerations applicable to any junior subordinated debt securities which are denominated in currencies other than U.S. dollars will be described in the prospectus supplement relating to that series of junior subordinated debt securities.

Unless we indicate otherwise in the applicable prospectus supplement, the junior subordinated debt securities will be denominated in U.S. dollars in minimum denominations of $1,000 and integral multiples thereof.

Subordination

Each series of junior subordinated debt securities will be subordinate and junior in right of payment, to the extent set forth in the Junior Subordinated Indenture, to all Senior Ranking Indebtedness (as defined below). If:

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then the holders of Senior Ranking Indebtedness generally will have the right to receive payment, in the case of the first instance above, of all amounts due or to become due upon that Senior Ranking Indebtedness, and, in the case of the second and third instances, of all amounts due on that Senior Ranking Indebtedness, or we will make provision for those payments, before the holders of any junior subordinated debt securities have the right to receive any payments of principal or interest on their securities. (Sections 14.1 and 14.9 of the Junior Subordinated Indenture).

“Senior Ranking Indebtedness” means, with respect to any series of junior subordinated debt securities, the principal, premium, interest and any other payment in respect of any of the following, whether outstanding on the date of execution of the Junior Subordinated Indenture or thereafter incurred, other than obligations expressly on a parity with or junior to the junior subordinated debt securities:

Senior Ranking Indebtedness will not include trade accounts payable, accrued liabilities arising in the ordinary course of business, indebtedness to our subsidiaries or any indebtedness which is by its terms junior to or on parity with the junior subordinated debt securities. (Section 1.3 of the Junior Subordinated Indenture.)

Senior Ranking Indebtedness will be entitled to the benefits of the subordination provisions in the Junior Subordinated Indenture irrespective of the amendment, modification or waiver of any term of the Senior Ranking Indebtedness. We may not amend the Junior Subordinated Indenture to change the subordination of any outstanding junior subordinated debt securities without the consent of each holder of junior subordinated debt securities that such amendment would adversely affect. (Sections 12.2 and 14.7 of the Junior Subordinated Indenture.)

The Junior Subordinated Indenture does not limit the amount of junior subordinated debt securities that we may issue.

Registration, Transfer and Exchange

Junior subordinated debt securities of any series may be exchanged for other junior subordinated debt securities of the same series of any authorized denominations and of a like aggregate principal amount, series and stated maturity and having the same terms and original issue date or dates. (Section 2.6 of the Junior Subordinated Indenture).

Unless we indicate otherwise in the applicable prospectus supplement, junior subordinated debt securities may be presented for registration of transfer (duly endorsed or accompanied by a duly executed written instrument of transfer), at the office of the Junior Subordinated Debt Trustee maintained for that purpose with

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respect to any series of junior subordinated debt securities and referred to in the applicable prospectus supplement, without service charge and upon payment of any taxes and other governmental charges as described in the Junior Subordinated Indenture. Any transfer or exchange will be effected if the junior subordinated debt securities are duly endorsed by, or accompanied by a written instrument or instruments of transfer in a form satisfactory to the Company and the Junior Subordinated Debt Trustee and duly executed by the holder of the junior subordinated debt security as described in the Junior Subordinated Indenture. (Section 2.6 of the Junior Subordinated Indenture).

The Junior Subordinated Debt Trustee will not be required to exchange or register a transfer of any junior subordinated debt securities of a series selected, called or being called for redemption except, in the case of any junior subordinated debt security to be redeemed in part, the portion thereof not to be so redeemed. (Section 2.6 of the Junior Subordinated Indenture). See the information under the heading “Book-Entry System” in this prospectus.

Payment and Paying Agents

Principal, interest and premium, if any, on junior subordinated debt securities issued in the form of global junior subordinated debt securities will be paid in the manner described below under the heading “Book-Entry System.” Unless we indicate otherwise in the applicable prospectus supplement, interest on junior subordinated debt securities that are in the form of certificated junior subordinated debt securities will be paid by check mailed to the holder at that person’s address as it appears in the register for the junior subordinated debt securities maintained by the Junior Subordinated Debt Trustee; however, a holder of $10,000,000 or more junior subordinated debt securities having the same interest payment dates will be entitled to receive payments of interest by wire transfer to a bank within the continental United States if appropriate wire transfer instructions have been received by the Junior Subordinated Debt Trustee on or prior to the applicable record date. (Section 2.12 of the Junior Subordinated Indenture). Unless we indicate otherwise in the applicable prospectus supplement, the principal, interest at maturity and premium, if any, on junior subordinated debt securities in the form of certificated junior subordinated debt securities will be payable in immediately available funds at the office of the Junior Subordinated Debt Trustee. (Section 2.12 of the Junior Subordinated Indenture).

All monies paid by us to a paying agent for the payment of principal, interest or premium, if any, on any junior subordinated debt security which remain unclaimed at the end of two years after that principal, interest or premium has become due and payable will be repaid to us and the holder of that junior subordinated debt security will thereafter look only to us for payment of that principal, interest or premium. (Section 4.4 of the Junior Subordinated Indenture).

Events of Default and Remedies

Unless we provide otherwise in a prospectus supplement, the following will constitute events of default under the Junior Subordinated Indenture with respect to the junior subordinated debt securities of any series:

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(Section 7.1 of the Junior Subordinated Indenture).

Acceleration of Maturity . If an event of default occurs and is continuing with respect to a series of junior subordinated debt securities, either the Junior Subordinated Debt Trustee or the holders of at least 25% in principal amount of the outstanding securities of that series may declare the principal amount of all securities of that series to be due and payable immediately. At any time after an acceleration of a series of securities has been declared, but before a judgment or decree of the immediate payment of the principal amount of those securities has been obtained, if:

then that holders’ rescission and the payment or deposit will cause an automatic rescission and annulment of the acceleration of the securities of that series. (Section 7.1 of the Junior Subordinated Indenture).

Indemnification of Junior Subordinated Debt Trustee . The Junior Subordinated Debt Trustee generally will be under no obligation to exercise any of its rights or powers under the Junior Subordinated Indenture at the request or direction of any of the holders unless such holders have offered reasonable security or indemnity to the Junior Subordinated Debt Trustee. (Section 8.2 of the Junior Subordinated Indenture).

Right to Direct Proceedings . The holders of a majority in principal amount of the outstanding securities of a series generally will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the Junior Subordinated Debt Trustee, or of exercising any trust or power conferred on the Junior Subordinated Debt Trustee, relating to the securities of that series. Notwithstanding, the Junior Subordinated Debt Trustee may refuse to follow any direction that conflicts with law or the Junior Subordinated Indenture or would expose the Junior Subordinated Debt Trustee to personal liability or be unduly prejudicial to holders not joining in such proceeding. (Section 7.7 of the Junior Subordinated Indenture).

Limitation on Rights to Institute Proceedings . No holder of the junior subordinated debt securities of a series will have any right to pursue a remedy under the Junior Subordinated Indenture, unless:

(Section 7.4 of the Junior Subordinated Indenture).

No Impairment of Right to Receive Payment . Notwithstanding any other provision of the Junior Subordinated Indenture, the holder of any junior subordinated debt security will have the absolute and unconditional right to receive payment of the principal, premium, if any, and interest on that junior subordinated debt security when due and payable, and to institute suit for enforcement of that payment. This right may not be impaired without the consent of the holder. (Section 7.4 of the Junior Subordinated Indenture).

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Notice of Default . The Junior Subordinated Debt Trustee is required to give the holders of a series of securities notice of the occurrence of a default within 90 days of the default with respect to that series, unless the default is cured or waived. Except in the case of a payment default on the junior subordinated debt securities, or a default in the payment of any sinking or purchase fund installments, the Junior Subordinated Debt Trustee may withhold the notice if its board of directors or trustees, executive committee, or a trust committee of directors or trustees or responsible officers determines in good faith that it is in the interest of holders of the series of affected securities to do so. (Section 7.8 of the Junior Subordinated Indenture). We are required to deliver to the Junior Subordinated Debt Trustee each year a certificate as to whether or not we are in compliance with the conditions and covenants under the Junior Subordinated Indenture. (Section 5.5 of the Junior Subordinated Indenture).

Conversion Rights

Any supplemental indenture establishing a series of junior subordinated debt securities may provide for conversion rights. We will describe in the applicable prospectus supplement the particular terms and conditions, if any, on which junior subordinated debt securities may be convertible into other securities. These terms will include the conversion rate, the conversion period, provisions as to whether conversion will be mandatory or at our option or the option of the holder, events requiring an adjustment of the conversion rate and provisions affecting conversion in the event of the redemption of the debt securities. If we issue convertible debt securities, we will need to supplement the indenture to add applicable provisions regarding conversion.

Defeasance and Discharge

We may be discharged from all obligations relating to the junior subordinated debt securities and the Junior Subordinated Indenture (except for specified obligations such as obligations to register the transfer or exchange of securities, replace stolen, lost or mutilated securities and maintain paying agencies) if we irrevocably deposit with the Junior Subordinated Debt Trustee, in trust for the benefit of holders of securities, money or U.S. government obligations (or any combination thereof) sufficient to make all payments of principal, premium and interest on the securities on the dates those payments are due. To discharge these obligations, we must deliver to the Junior Subordinated Debt Trustee an opinion of counsel to the effect that we have received from, or there has been published by, the Internal Revenue Service a ruling or similar pronouncement by the Internal Revenue Service or that there has been a change in law, in either case to the effect that the holders of the securities will not recognize income, gain or loss for federal income tax purposes as a result of such defeasance or discharge of the Junior Subordinated Indenture, and holders will be subject to tax in the same manner, in the same amounts and same time as would have been the case absent such defeasance. Upon any discharge of our obligations as described above, we will be deemed to have paid and discharged our entire indebtedness represented by the junior subordinated debt securities and our obligations under the junior subordinated debt securities. (Section 4.1 of the Junior Subordinated Indenture).

Modification

Unless we indicate otherwise in the applicable prospectus supplement, we and the Junior Subordinated Debt Trustee may modify and amend the Junior Subordinated Indenture from time to time.

We will not need the consent of the holders for the following types of amendments:

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(Section 12.1 of the Junior Subordinated Indenture).

We will need the consent of the holders of each outstanding security affected by a proposed amendment if the amendment would cause any of the following to occur:

(Section 12.2 of the Junior Subordinated Indenture).

Amendments other than those described in the above two paragraphs will require the approval of a majority in principal amount of the outstanding securities of all series, provided that if there are securities of more than one series outstanding and if a proposed amendment would directly affect the rights of holders of securities of one or more, but less than all, of such series, then the approval of a majority in principal amount of the outstanding securities of all series so directly affected, considered as one class, will be required.

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Consolidation, Merger and Sale of Assets; No Financial Covenants

We will not consolidate with or merge into any other corporation or sell, or otherwise dispose all or substantially all of our assets unless the successor or transferee corporation assumes by supplemental indenture our obligations to pay the principal, interest and premium on all the securities and our obligation to perform every covenant of the Junior Subordinated Indenture that we are to perform or observe, and we or the successor or transferee corporation, as applicable, are not immediately following such consolidation or merger, or sale, or disposition in default in the performance of any such covenant. Upon any consolidation or merger, or any sale, transfer or other disposition of all or substantially all of our assets, the successor or transferee corporation will succeed to, and be substituted for, and may exercise all of our rights and powers under the Junior Subordinated Indenture with the same effect as if the successor corporation had been named as us in the Junior Subordinated Indenture and we will be released from all obligations under the Junior Subordinated Indenture. Regardless of whether a sale or transfer of assets might otherwise be considered a sale of all or substantially all of our assets, the Junior Subordinated Indenture also specifically permits any sale, transfer or conveyance of our non-utility subsidiaries if, following such sale or transfer, the securities are rated by Standard & Poor’s Ratings Group and Moody’s Investors Service, Inc. at least as high as the ratings accorded the securities immediately prior to the sale, transfer or disposition. (Sections 11.1 and 11.2 of the Junior Subordinated Indenture).

The Junior Subordinated Indenture does not contain any financial or other similar restrictive covenants.

Resignation or Removal of Junior Subordinated Debt Trustee

The Junior Subordinated Debt Trustee may resign with respect to securities of any series at any time by notifying us in writing and specifying the day that the resignation is to take effect. The resignation will not take effect, however, until the later of the appointment of a successor trustee and the day the resignation is to take effect. (Section 8.10 of the Junior Subordinated Indenture).

The holders of a majority in principal amount of the outstanding securities of any series may remove the Junior Subordinated Debt Trustee as trustee of that series of securities at any time. In addition, so long as no event of default or event which, with the giving of notice or lapse of time or both, would become an event of default has occurred and is continuing with respect to securities of any series, we may remove the Junior Subordinated Debt Trustee with respect to securities of that series upon notice to the holder of each security of that series outstanding and written notice to the Junior Subordinated Debt Trustee. (Section 8.10 of the Junior Subordinated Indenture).

Governing Law

The Junior Subordinated Indenture and the junior subordinated debt securities will be governed by, and will be construed in accordance with, the laws of the State of Minnesota. (Section 15.4 of the Junior Subordinated Indenture).

Concerning the Junior Subordinated Debt Trustee

Wells Fargo Bank, National Association is the Junior Subordinated Debt Trustee. We maintain banking relationships with the Junior Subordinated Debt Trustee in the ordinary course of business. The Junior Subordinated Debt Trustee also acts as trustee for our senior debt securities and certain debt securities of our subsidiaries.

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DESCRIPTION OF COMMON STOCK

The following summary description sets forth some of the general terms and provisions of the common stock. This summary is not complete. For a more detailed description of the common stock, you should refer to the provisions of our Amended and Restated Articles of Incorporation (“Articles”) and Bylaws. The Articles and the Bylaws have been filed as exhibits to the registration statement. You should read them for provisions that may be important to you.

General

Our capital stock consists of two classes: common stock, par value $2.50 per share (1,000,000,000 shares currently authorized of which 508,064,983 shares were outstanding as of February 19, 2018); and preferred stock, par value $100 per share (7,000,000 shares authorized, of which no shares were outstanding as of February 19, 2018).

Dividend Rights

Before we can pay any dividends on our common stock, the holders of our preferred stock, if any, are entitled to receive dividends at the respective rates provided for in the terms of the shares of any outstanding series.

Because we are a holding company and conduct all of our operations through our subsidiaries, our cash flow and ability to pay dividends is dependent on the earnings and cash flows of our subsidiaries and the distribution or other payment of those earnings to us in the form of dividends, or in the form of repayments of loans or advances to us. Some of our subsidiaries may have restrictions on their ability to pay dividends including covenants under their borrowing arrangements and mortgage indentures, and possibly also restrictions imposed by their regulators and by statute. See “Management’s Discussion and Analysis of Financial Conditions and Results of Operations — Common Stock Dividends” and Notes to Consolidated Financial Statements in our most recent Annual Report on Form 10-K for a discussion of factors affecting our payment of dividends including limitations imposed by statute.

Voting Rights

The holders of our common stock are entitled to one vote for each share held on all matters submitted to a vote of our stockholders.

Preferred Stock

Our board of directors is authorized, to the fullest extent permitted by law, to establish out of our authorized capital stock up to 7,000,000 shares of preferred stock, which may be issued in one or more classes or series, having such dividend rights and times of payment, redemption prices, liquidation prices or preferences as to assets in voluntary liquidation, and other relative rights and preferences as our board of directors shall determine. As of February 19, 2018, no shares of preferred stock were outstanding. The terms of any preferred stock issued by the Company could have the effect of delaying or preventing a change in control without further action by our shareholders. The issuance of shares of preferred stock with voting and conversion rights may adversely affect the voting power of the holders of our common stock.

Change of Control

Our Bylaws and the Minnesota Business Corporation Act, as amended (the “Minnesota BCA”), contain provisions that could discourage, delay, prevent or make more difficult a change of control of our company. including, but not limited to, those summarized below.

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Bylaw Provisions . Under our Bylaws, our shareholders must provide us advance notice of the introduction by them of business at annual meetings of our shareholders. For a shareholder to properly bring a proposal before an annual meeting, the shareholder must comply with the shareholder proposal requirements under the federal proxy rules and deliver a written notice to our Corporate Secretary, or mail and be received at our principal executive office, not less than ninety days before the first anniversary date of the preceding year’s annual meeting. If, however, the date of the annual meeting is more than thirty days before or after such anniversary date, the notice must be so delivered or so mailed and received not less than ninety days before the annual meeting or, if later, within ten days after the first public announcement of the date of the annual meeting. The required notice from a shareholder must contain a description of the business being introduced, the reasons for introducing such business, the name and address of each shareholder supporting the introduction and such other information as required under our Bylaws and federal proxy rules.

A shareholder, or a group of up to 20 shareholders, owning 3% or more of the Company’s outstanding common stock continuously for at least 3 years can nominate and include in the Company’s proxy materials director-nominees constituting up to 2 individuals or 20% of the board (whichever is greater), provided that the shareholder(s) and the director-nominee(s) satisfy the requirements specified in the Bylaws. To be timely, the proposal must be delivered to the Secretary, or mailed and received at our principal executive office, not less than 120 days and not more than 150 days prior to the first anniversary of the date that the Company distributed its proxy statement to shareholders for the previous year’s annual meeting of shareholders. If, however, the date of the annual meeting of shareholders is more than thirty (30) days before or after such anniversary date, the Notice of Proxy Access Nomination shall be timely if so delivered or so mailed and received not less than ninety (90) days before the annual meeting or, if later, within ten (10) days after the first public announcement of the date of the annual meeting. The required notice from such a shareholder must contain such information as required under our Bylaws and federal proxy rules.

Except to the extent otherwise required by law, the adjournment of an annual meeting of shareholders will not commence a new time period for the giving of a shareholder’s notice as required above.

Minnesota BCA . Section 302A.671 of the Minnesota BCA applies to potential acquirers of 20% or more of our voting shares. Section 302A.671 provides in substance that shares acquired by such acquirer will not have any voting rights unless the voting rights are either:

Section 302A.673 of the Minnesota BCA generally prohibits public Minnesota corporations, including us, from engaging in any business combination with a person or entity owning, directly or indirectly, 10% or more of our voting shares for a period of four years after the date of the transaction in which such person or entity became a 10% shareholder unless the business combination or the acquisition resulting in 10% ownership was approved by a committee of disinterested directors prior to the date such person or entity became a 10% shareholder.

Section 302A.675 of the Minnesota BCA provides in substance that a person or entity making a takeover offer (an “offeror”) for us is prohibited from acquiring any additional shares of our company within two years following the last purchase of shares pursuant to the offer with respect to that class unless (i) the acquisition is approved by a committee of disinterested directors before the purchase of any shares by the offeror pursuant to the offer or (ii) our shareholders are afforded, at the time of the acquisition, a reasonable opportunity to dispose of their shares to the offeror upon substantially equivalent terms as those provided in the earlier takeover offer.

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Liquidation Rights

If we were to liquidate, subject to the terms of any outstanding series of preferred stock, the holders of our common stock are entitled to receive pro rata our assets legally available for distribution to stockholders.

Preemptive and Subscription Rights

No holder of our capital stock has the preemptive right to purchase or subscribe for any additional shares of our capital stock.

DESCRIPTION OF PREFERRED STOCK

Our board of directors is authorized, to the fullest extent permitted by law, to establish out of our authorized capital stock up to 7,000,000 shares of preferred stock, which may be issued in one or more classes or series, having such dividend rights and times of payment, redemption prices, liquidation prices or preferences, and the other rights and preferences as our board of directors shall determine at the time of issuance. As of February 19, 2018, no shares of preferred stock were outstanding.

The issuance of our preferred stock, while potentially providing us with flexibility in connection with possible acquisitions and other corporate purposes, could have the effect of making it more difficult for a third party to acquire, or delay or deter a third party from attempting to acquire, a majority of our outstanding voting stock.

The rights, preferences, privileges and restrictions of the preferred stock of each series will be fixed by resolution of the board of directors. To the extent appropriate, we will include in a prospectus supplement the terms relating to any series of preferred stock being offered thereby. These terms will include some or all of the following, as applicable:

The Minnesota BCA provides that the holders of preferred stock have the right to vote separately as a class on any proposal involving changes in the rights or preferences of holders of such preferred stock. This right is in addition to any voting rights that may be provided for in the applicable resolution creating such preferred stock.

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DESCRIPTION OF DEPOSITARY SHARES

We may offer depositary shares (either separately or together with other securities) representing fractional interests in our preferred stock of any series. The following description sets forth certain general terms and provisions of the depositary shares to which any prospectus supplement may relate. The particular terms of the depositary shares to which any prospectus supplement may relate and the extent, if any, to which the general terms and provisions may apply to the depositary shares so offered will be described in the applicable prospectus supplement. To the extent that any particular terms of the depositary shares, deposit agreements and depositary receipts described in a prospectus supplement differ from any of the terms described below, then the terms described below will be deemed to have been superseded by that prospectus supplement. We encourage you to read the applicable deposit agreement and depositary receipts for additional information before you decide whether to purchase any of our depositary shares.

In connection with the issuance of any depositary shares, we will enter into a deposit agreement with a bank or trust company, as depositary, which will be named in the applicable prospectus supplement. Depositary shares will be evidenced by depositary receipts issued pursuant to the related deposit agreement. Immediately following our issuance of the security related to the depositary shares, we will deposit the shares of our preferred stock with the relevant depositary and will cause the depositary to issue, on our behalf, the related depositary receipts. Subject to the terms of the deposit agreement, each owner of a depositary receipt will be entitled, in proportion to the fractional interest in the share of preferred stock represented by the related depositary share, to all the rights, preferences and privileges of, and will be subject to all of the limitations and restrictions on, the preferred stock represented by the depositary receipt (including, if applicable, dividend, voting, conversion, exchange, redemption, sinking fund, subscription and liquidation rights). To the extent appropriate, the applicable prospectus supplement will describe the specific terms of the depositary shares offered thereby. The terms of any offered depositary shares will be described in a supplement to this prospectus.

DESCRIPTION OF WARRANTS

We may issue warrants to purchase debt securities, common stock, preferred stock, depositary shares, or any combination thereof, with or without the payment of separate consideration therefor (including by means of a dividend or similar distribution to holders of our outstanding securities). We may issue warrants independently or together with any other securities offered by a prospectus supplement. Warrants may be attached to or separate from such securities and may or may not be transferable. Each series of warrants will be issued under a separate warrant agreement we will enter into with a warrant agent specified in the applicable prospectus supplement. The warrant agent will act solely as our agent in connection with the warrants of a particular series and will not assume any obligation or relationship of agency or trust for or with any holders or beneficial owners of warrants. In connection with any warrants, we may enter into a standby underwriting agreement with one or more underwriters pursuant to which the underwriters will agree to purchase any securities underlying such warrants that remain unpurchased upon the expiration of such warrants. To the extent appropriate, the applicable prospectus supplement will describe the specific terms of the warrants offered thereby.

DESCRIPTION OF RIGHTS

We may issue subscription rights to purchase shares of our common stock or preferred stock. These subscription rights may be issued independently or together with any other security offered hereby and may or may not be transferable by the stockholder receiving the subscription rights in such offering. In connection with any offering of subscription rights, we may enter into a standby arrangement with one or more underwriters or other investors pursuant to which the underwriters or other investors may be required to purchase any securities remaining unsubscribed for after such offering. To the extent appropriate, the applicable prospectus supplement will describe the specific terms of the rights offered thereby.

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DESCRIPTION OF PURCHASE CONTRACTS

We may issue purchase contracts, including contracts obligating holders to purchase from us, and for us to sell to holders, a specific or varying number of debt securities, shares of our common stock or preferred stock, depositary shares, warrants, rights or other property or any combination of the above, at a future date or dates. Alternatively, the purchase contracts may obligate us to purchase from holders, and obligate holders to sell to us, a specific or varying number of debt securities, shares of our common stock or preferred stock, depositary shares, warrants, rights or other property. The price of such debt securities, shares of our common stock or preferred stock, depositary shares, warrants, rights or other property may be fixed at the time the purchase contracts are issued or may be determined by reference to a specific formula described in the purchase contracts. We may issue purchase contracts separately or as a part of units each consisting of a purchase contract and one or more of our other securities described in this prospectus or debt obligations of third parties, such as U.S. Treasury securities, securing the holder’s obligations under the purchase contract. The purchase contracts may require us to make periodic payments to holders or vice versa and the payments may be unsecured or pre-funded on some basis. The purchase contracts may require holders to secure the holder’s obligations in a specified manner that we will file with the SEC in connection with a public offering relating to the purchase contracts. To the extent appropriate, the applicable prospectus supplement will describe the specific terms of the purchase contracts offered thereby.

DESCRIPTION OF UNITS

We may issue units comprising one or more securities described in this prospectus in any combination. Units may also include debt obligations of third parties, such as U.S. Treasury securities. Each unit may be issued so that the holder of the unit also is the holder of each security included in the unit. Thus, the unit may have the rights and obligations of a holder of each included security. The unit agreement under which a unit is issued may provide that the securities included in the unit may not be held or transferred separately at any time or at any time before a specified date. To the extent appropriate, the applicable prospectus supplement will describe the specific terms of the units offered thereby.

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BOOK-ENTRY SYSTEM

Unless otherwise specified in the applicable prospectus supplement, each series of securities offered by this prospectus will be issued as fully-registered global securities representing all or part of that series of securities. This means that we will not issue certificates for that series of securities to the holders. Instead, a global security representing that series of securities will be deposited with, or on behalf of, DTC or its successor, as the depository. The global securities will be registered at the request of DTC in the name of Cede & Co., DTC’s nominee, or such other name as may be requested by an authorized representative of DTC.

DTC will keep an electronic record of its participants (for example, your broker) whose clients have purchased securities represented by a global security. Unless a global security is exchanged in whole or in part for a certificated security, a global security may not be transferred, except that DTC, its nominees and successors may transfer a global security as a whole to one another.

Beneficial interests in global securities will be shown on, and transfers of interests will be made only through, records maintained by DTC and its participants. The laws of some jurisdictions require that some purchasers take physical delivery of securities in definitive form. These laws may impair the ability to transfer beneficial interests in a global security.

We will make payments of principal, interest, if any, and premium, if any, to DTC or its nominee. We, the applicable trustee and any paying agent will treat DTC or its nominee as the owner of the global security for all purposes, including any notices and voting. Accordingly, neither we nor any trustee nor any paying agent will have any direct responsibility or liability to pay amounts due on a global security to owners of beneficial interests in a global security.

DTC is a limited-purpose trust company organized under the New York Banking Law, a “banking organization” within the meaning of the New York Banking Law, a member of the Federal Reserve System, a “clearing corporation” within the meaning of the New York Uniform Commercial Code and a “clearing agency” registered pursuant to the provisions of Section 17A of the Exchange Act. DTC holds securities that its participants, or “direct participants,” deposit with DTC. DTC also facilitates the post-trade settlement among direct participants of sales and other securities transactions in deposited securities through electronic computerized book-entry transfers and pledges between direct participants’ accounts. This eliminates the need for physical movement of securities certificates. Direct participants include both U.S. and non-U.S. securities brokers and dealers, banks, trust companies, clearing corporations and certain other organizations. DTC is a wholly owned subsidiary of The Depository Trust & Clearing Corporation, or “DTCC.” DTCC is the holding company for DTC, National Securities Clearing Corporation and Fixed Income Clearing Corporation, all of which are registered clearing agencies. DTCC is owned by the users of its regulated subsidiaries. Access to the DTC system is also available to others such as both U.S. and non-U.S. securities brokers and dealers, banks, trust companies and clearing corporations that clear through or maintain a custodial relationship with a direct participant either directly or indirectly, an “indirect participant.” Direct participants and indirect participants are referred to collectively as “participants.” The DTC Rules applicable to its participants are on file with the SEC.

Purchases of global securities under the DTC system must be made by or through direct participants, which will receive a credit for the securities on DTC’s records. The ownership interest of each actual purchaser of each security, or “beneficial owner,” is in turn to be recorded on the direct and indirect participants’ records. Beneficial owners will not receive written confirmation from DTC of their purchase. Beneficial owners are, however, expected to receive written confirmations providing details of the transaction, as well as periodic statements of their holdings, from the direct or indirect participant through which the beneficial owner entered into the transaction. Transfers of ownership interests in the global securities are to be accomplished by entries made on the books of direct and indirect participants acting on behalf of beneficial owners. Beneficial owners will not receive certificates representing their ownership interests in the global securities, except in the event that use of the book-entry system for the global securities is discontinued.

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To facilitate subsequent transfers, all securities deposited by direct participants with DTC are registered in the name of Cede & Co. or such other name as may be requested by an authorized representative of DTC. The deposit of securities with DTC and their registration in the name of Cede & Co. or such other nominee do not effect any change in beneficial ownership. DTC has no knowledge of the actual beneficial owners of the securities. DTC’s records reflect only the identity of the direct participants to whose accounts such securities are credited, which may or may not be the beneficial owners. The direct and indirect participants remain responsible for keeping account of their holdings on behalf of their customers.

Conveyance of notices and other communications by DTC to direct participants, by direct participants to indirect participants and by direct participants and indirect participants to beneficial owners will be governed by arrangements among them, subject to any statutory or regulatory requirements as may be in effect from time to time.

If a particular series of securities is redeemable at our option or at the option of the holder, redemption notices will be sent to DTC. If less than all of the securities of a series are being redeemed, DTC’s practice is to determine by lot the amount of the interest of each direct participant in such series to be redeemed. Redemption proceeds and distributions on global securities will be made to Cede & Co. or such other nominee as may be requested by an authorized representative of DTC. Upon DTC’s receipt of funds and corresponding detail information from us, any trustee or any paying agent, DTC’s practice is to credit direct participants’ accounts in accordance with the holdings information shown on DTC’s records on the payment date. Payments by participants to beneficial owners of securities will be governed by standing instructions and customary practices, as is the case with securities held for the accounts of customers in bearer form or registered in “street name.” Payments will be the responsibility of such participant and not of DTC nor its nominee, any trustee, any paying agent or us, subject to any statutory or regulatory requirements. Payment of redemption proceeds and distributions to Cede & Co. or such other nominee as may be requested by an authorized representative of DTC is the responsibility of us, the applicable trustee or the applicable paying agent, disbursement of such payments to direct participants will be the responsibility of DTC, and disbursement of such payments to the beneficial owners will be the responsibility of direct and indirect participants.

Neither DTC nor Cede & Co. or any other DTC nominee will consent or vote with respect to global securities unless authorized by a direct participant in accordance with DTC’s procedures. Under its usual procedures, DTC mails an omnibus proxy to us as soon as possible after the record date. The omnibus proxy assigns Cede & Co.’s consenting or voting rights to those direct participants to whose accounts the securities are credited on the record date as identified in a listing attached to the omnibus proxy.

Global securities will be exchangeable for corresponding certificated securities registered in the name of persons other than DTC or its nominee if (1) DTC (a) notifies us that it is unwilling or unable to continue as depository for any of the global securities or (b) at any time ceases to be a clearing agency registered under the Exchange Act, (2) an event of default occurs and is continuing with respect to the applicable series of securities or (3) we execute and deliver to the applicable trustee an order that the global securities will be so exchangeable.

The information in this section concerning DTC and DTC’s book-entry system has been obtained from DTC, and we and any underwriters, dealers or agents are not responsible for the accuracy of the information or for the performance by DTC of its obligations under the rules and procedures governing its operations or otherwise.

Any underwriters, dealers or agents of any securities may be direct participants of DTC.

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DESCRIPTION OF THE FIRST MORTGAGE BONDS

The description below contains a summary of selected provisions of the indenture, including supplemental indentures, under which the first mortgage bonds will be issued. This summary is not complete. The indenture and the form of supplemental indenture applicable to the first mortgage bonds have been filed as exhibits to the registration statement of which this prospectus constitutes a part. You should read them for provisions that may be important to you. In the summary below, we have included references to section numbers of the indenture so that you can easily locate these provisions.

We are not required to issue future issues of indebtedness under the indenture described below. We are free to use other indentures or documentation, containing provisions different from those described in this prospectus, in connection with future issues of other indebtedness not issued under this prospectus.

The first mortgage bonds will be represented either by global securities registered in the name of The Depository Trust Company, or DTC, as depository, or Depository, or its nominee, or by securities in certificated form issued to the registered owners, as set forth in the applicable prospectus supplement. See the information under the caption “Book-Entry System” in this prospectus.

General

We may issue the first mortgage bonds from time to time in one or more new series under the Supplemental and Restated Trust Indenture dated May 1, 1988, which we refer to as the Restated Indenture, as previously supplemented by 29 supplemental trust indentures and as to be supplemented by one or more new supplemental indentures for the first mortgage bonds, which we collectively refer to as the Mortgage Indenture, all from us to The Bank of New York Mellon Trust Company, N.A., as successor trustee, which we refer to as the Mortgage Trustee. The Mortgage Indenture will govern the first mortgage bonds offered by this prospectus. As of December 31, 2017, there were 15 series of first mortgage bonds in an aggregate principal amount of approximately $5.0 billion outstanding under the Mortgage Indenture.

The holders of the outstanding first mortgage bonds do not, and, unless the prospectus supplement that describes a particular series of first mortgage bonds provides otherwise with respect to that series, the holders of any first mortgage bonds offered by this prospectus will not, have the right to require us to repurchase the first mortgage bonds if we become involved in a highly leveraged or change in control transaction. The Mortgage Indenture does not have any provision that is designed specifically in response to highly leveraged or change in control transactions.

When we offer to sell a particular series of first mortgage bonds, we will describe the specific terms of that series in a prospectus supplement relating to that series, including the following terms:

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Unless the prospectus supplement that describes a particular series of first mortgage bonds provides otherwise, we may from time to time, without the consent of the holders of that series of first mortgage bonds, reopen such series of first mortgage bonds and issue additional first mortgage bonds with the same terms (including maturity and interest payment terms) as such series of first mortgage bonds.

Redemption

The prospectus supplement that describes a particular series of first mortgage bonds will set forth any terms for the optional or mandatory redemption of that particular series.

Security for the First Mortgage Bonds

The first mortgage bonds being issued pursuant to this prospectus will be secured equally and ratably with all of our other outstanding first mortgage bonds by a valid and direct first mortgage lien on all of the real and fixed properties, leasehold rights, franchises and permits then owned by us subject only to permitted encumbrances (as discussed below).

The Mortgage Indenture subjects to the lien of the Mortgage Indenture all of our property, rights and franchises, except as otherwise expressly provided. These provisions might not be effective as to property acquired within 90 days prior and subsequent to the filing of a case by us under the United States Bankruptcy Code.

The Mortgage Indenture provides that no liens prior or equal to the lien of the Mortgage Indenture, other than permitted encumbrances, may be created or permitted to exist on the mortgaged and pledged property whether now owned or acquired in the future. (Section 8.04 of the Restated Indenture.)

Permitted encumbrances include, among others, the following:

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(Section 1.03 of the Restated Indenture.)

The holders of 66 2/3% of the principal amount of first mortgage bonds outstanding may (1) consent to the creation or existence of a prior lien with respect to up to 50% of the sum of our depreciable property and land, after giving effect to the prior lien or (2) terminate the lien of the Mortgage Indenture with respect to up to 50% of the sum of our depreciable property and land. (Section 18.02(e) of the Restated Indenture.)

Sinking Fund Provisions

We currently do not have any outstanding first mortgage bonds that are, and, unless the prospectus supplement that describes a particular series of first mortgage bonds provides otherwise with respect to that series, the first mortgage bonds offered by this prospectus will not be, subject to a sinking fund.

Maintenance Provisions

As a maintenance fund for the first mortgage bonds, we have agreed to pay to the Mortgage Trustee on each May 1 an amount equal to 2.50% of our completed depreciable property as of the end of the preceding calendar year, after deducting credits at our option for the following:

(Section 9.01 of the Restated Indenture.)

We may withdraw moneys from the maintenance fund in amounts equal to retirements of first mortgage bonds and permanent additions. Cash on deposit in the maintenance fund may be used for the purchase or redemption of first mortgage bonds. Any redemption of this nature would be at the applicable regular redemption price of the first mortgage bonds to be redeemed and subject to any restrictions on the redemption of that first mortgage bond. (Sections 9.03 and 9.04 of the Restated Indenture).

To the extent that maintenance fund credits exceed 2.50% of completed depreciable property for any year after 1987, such excess credits may be applied in future years (1) to offset any maintenance fund deficiency or (2) to increase the amount of established permanent additions available for use under the Mortgage Indenture. (Section 9.05 of the Restated Indenture.)

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We have agreed to maintain our properties in adequate repair, working order and condition. (Section 8.06 of the Restated Indenture.)

Issuance of Additional First Mortgage Bonds

The maximum principal amount of first mortgage bonds that we may issue under the Mortgage Indenture is not limited, except as described below. We may issue additional first mortgage bonds in amounts equal to (1) 66 2/3% of the cost or fair value, whichever is less, of permanent additions after deducting retirements (Article V of the Restated Indenture); (2) retired first mortgage bonds, which have not been otherwise used under the Mortgage Indenture (Article VI of the Restated Indenture); or (3) the amount of cash deposited with the Mortgage Trustee, which cash may be withdrawn on the same basis as additional first mortgage bonds may be issued under clauses (1) and (2) above. (Article VII of the Restated Indenture.)

The first mortgage bonds issued pursuant to this prospectus will be issued under clause (1) or (2) above. At December 31, 2017, the amount of net permanent additions available for the issuance of first mortgage bonds was approximately $9.957 billion, which could be used to authenticate up to approximately $6.638 billion principal amount of the first mortgage bonds. As of December 31, 2017, $564.995 million of retired first mortgage bonds were available to authenticate up to $564.995 million of first mortgage bonds.

We may not issue any additional first mortgage bonds on the basis of clause (1), clause (2) under specified conditions or clause (3), unless the earnings applicable to bond interest for a specified 12-month period are equal to twice the annual interest requirements on the first mortgage bonds, including those about to be issued, and any obligations secured by prior liens and any indebtedness secured by permitted encumbrances. (Sections 5.04, 6.02 and 7.01 of the Restated Indenture.) The calculation of earnings applicable to bond interest includes all of our nonutility revenues. (Section 1.03 of the Restated Indenture.)

Permanent additions include the following:

(Section 1.03 of the Restated Indenture.)

Earnings applicable to bond interest for the 12 months ended December 31, 2017 would be 4.07 times the annual interest requirements on our first mortgage bonds and any obligations secured by prior liens and any indebtedness secured by permitted encumbrances. Additional first mortgage bonds may vary as to maturity, interest rate, redemption prices and sinking fund, among other things. (Article II of the Restated Indenture.)

Provisions Limiting Dividends on Common Stock

We have agreed that the sum of:

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In computing net income for the purpose of this covenant, we will deduct the amount, if any, by which, after the date commencing 365 days prior to the effective date, the actual expenditures or charges for ordinary repairs and maintenance and the charges for reserves, renewals, replacements, retirements, depreciation and depletion are less than 2.50% of our completed depreciable property. (Section 8.07 of the Restated Indenture.)

Release Provisions

The Mortgage Indenture permits the release from its lien of any property upon depositing or pledging cash or certain other property of comparable fair value. The Mortgage Indenture also permits the following, in each case without any release or consent by the Mortgage Trustee or accountability to the Mortgage Trustee for any consideration received by us:

(Article XI of the Restated Indenture.)

Any of the mortgaged and pledged property may be released from the lien of the Mortgage Indenture if, after the release, the fair value of the remaining mortgaged and pledged property equals or exceeds a sum equal to 150% of the aggregate principal amount of first mortgage bonds outstanding. (Section 11.03(k) of the Restated Indenture.) Upon satisfaction of the requirements set forth in the Mortgage Indenture, this provision would permit us to spin off or otherwise dispose of a substantial amount of assets or a line of business without depositing cash or property with the Mortgage Trustee or obtaining the consent of the holders of the first mortgage bonds.

Modification of the Mortgage Indenture

We and the Mortgage Trustee may modify and amend the Mortgage Indenture from time to time. We will not need the consent of the holders of the first mortgage bonds for the following types of amendments, among others:

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(Section 18.01 of the Restated Indenture.)

With the consent of the holders of 66 2/3% in principal amount of the first mortgage bonds outstanding so affected, other provisions of the Mortgage Indenture may be changed except that, among other things, the following may not be done without the consent of the holders of each first mortgage bond so affected:

(Section 18.02 of the Restated Indenture.)

Defaults

The following is a summary of events defined in the Mortgage Indenture as completed defaults:

(Section 13.01 of the Restated Indenture.)

Notice of Default. The Mortgage Trustee is required to give notice to bondholders within 90 days after the occurrence of a default, unless the default has been cured or waived before giving its notice; provided that, except in the case of a default resulting from the failure to make any payment of principal or interest on any first mortgage bonds or to make any sinking fund payment, the Mortgage Trustee may withhold the notice if its board of directors, executive committee or a trust committee of directors or responsible officers determines in good faith that withholding the notice is in the interest of the bondholders. (Section 16.02 of the Restated Indenture.)

Acceleration of Maturity. In case of a completed default, the Mortgage Trustee may, and upon request of the holders of 25% in principal amount of the first mortgage bonds outstanding will, declare the first mortgage bonds due and payable, subject to the right of the holders of a majority of the first mortgage bonds then-outstanding to rescind or annul such action. Further, the Mortgage Trustee is obligated to take the actions provided in the Mortgage Indenture to enforce payment of the first mortgage bonds and the lien of the Mortgage Indenture upon being requested to do so by the holders of a majority in principal amount of the first mortgage

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bonds. However, the holders of a majority in principal amount of the first mortgage bonds may direct the taking of any of these actions or the refraining from these actions as is not in violation of the law or the Mortgage Indenture. Before taking these actions, the Mortgage Trustee may require adequate indemnity against the costs, expenses and liabilities to be incurred in connection with these actions. (Article XIII of the Restated Indenture.)

Compliance Certificate. We are required to file with the Mortgage Trustee information, documents and reports regarding our compliance with the conditions and covenants of the Mortgage Indenture as may be required by the rules and regulations of the SEC, including a certificate, furnished at least annually, as to whether, in the opinion of the officer signing such certificate, we are in compliance with the conditions and covenants under the Mortgage Indenture. (Section 8.18 of the Restated Indenture.)

Other Provisions

Whenever all indebtedness secured by the Mortgage Indenture has been paid, or adequate provision for payment has been made, the Mortgage Trustee will cancel and discharge the Mortgage Indenture. (Article XVII of the Restated Indenture.) We may deposit with the Mortgage Trustee any combination of cash or government obligations in order to provide for the payment of any series or all of the first mortgage bonds outstanding. The Mortgage Indenture also provides that we must furnish to the Mortgage Trustee officers’ certificates, certificates of an engineer, appraiser or other expert and, in some cases, accountants’ certificates in connection with the authentication of first mortgage bonds, the release or release and substitution of property and some other matters, and opinions of counsel as to the lien of the Mortgage Indenture and some other matters. (Articles IV, V, VI, VII, XI and XVII and Section 20.08 of the Restated Indenture.)

Concerning the Trustee

The Bank of New York Mellon Trust Company, N.A., is the Mortgage Trustee under the Mortgage Indenture. We maintain banking relationships with the Mortgage Trustee in the ordinary course of business.

Governing Law

The Mortgage Indenture and first mortgage bonds being issued pursuant to this prospectus are governed by, and construed in accordance with, the laws of the State of Minnesota.

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DESCRIPTION OF THE SENIOR UNSECURED DEBT SECURITIES

The description below contains a summary of selected provisions of the indenture, including supplemental indentures, under which the senior unsecured debt securities, which we refer to as debt securities, will be issued. This summary is not complete. The indenture and the form of supplemental indenture applicable to the debt securities have been filed as exhibits to the registration statement of which this prospectus is a part. You should read them for provisions that may be important to you. In the summary below, we have included references to section numbers of the indenture so that you can easily locate these provisions.

We are not required to issue future issues of indebtedness under the indenture described below. We are free to use other indentures or documentation, containing provisions different from those described in this prospectus, in connection with future issues of other indebtedness not issued under this prospectus.

The debt securities will be represented either by global securities registered in the name of DTC, as Depository, or its nominee, or by securities in certificated form issued to the registered owners, as set forth in the applicable prospectus supplement. See the information under the caption “Book-Entry System” in this prospectus.

General

The debt securities will be issued in one or more new series under the Indenture dated July 1, 1999, as supplemented, between us and Wells Fargo Bank, N.A., (as successor by merger to Norwest Bank Minnesota, National Association) as trustee, which we refer to as the Senior Trustee. This indenture, as previously supplemented by supplemental indentures and as to be supplemented by one or more new supplemental indentures for the debt securities, is referred to in this prospectus as the Senior Indenture. As of December 31, 2017, there were no debt securities outstanding under the Senior Indenture.

Unless the supplemental indenture that describes a particular series of debt securities provides otherwise with respect to that series, the holders of any debt securities offered by this prospectus will not, have the right to require us to repurchase the debt securities if we become involved in a highly leveraged or change in control transaction. The Senior Indenture does not have any provision that is designed specifically in response to highly leveraged or change in control transactions.

The debt securities will be our senior unsecured obligations and will rank on a parity with our other senior unsecured indebtedness. In this “Description of the Senior Unsecured Debt Securities,” we refer to securities issued under the Senior Indenture as the securities. Our secured debt will have a prior claim on the assets pledged to secure such debt and, therefore, our securities will be effectively subordinated to all of our current and future secured debt, including our first mortgage bonds to the extent of the value of the properties securing them. As of December 31, 2017, we had $5.0 billion of secured debt outstanding.

The amount of securities that we may issue under the Senior Indenture is not limited.

When we offer to sell a particular series of debt securities, we will describe the specific terms of that series in a prospectus supplement relating to that series, including the following terms:

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Unless the prospectus supplement that describes a particular series of debt securities provides otherwise, we may from time to time, without the consent of the holders of that series of debt securities, reopen such series of debt securities and issue additional debt securities with the same terms (including maturity and interest payment terms) as such series of debt securities.

Registration, Transfer and Exchange

Debt securities of any series may be exchanged for other debt securities of the same series of any authorized denominations and of a like aggregate principal amount and kind. (Section 2.6 of the Senior Indenture.)

Unless the prospectus supplement that describes a particular series of debt securities provides otherwise with respect to that series, debt securities may be presented for registration of transfer (duly endorsed or accompanied by a duly executed written instrument of transfer) at the office of the Senior Trustee maintained for that purpose and referred to in the applicable prospectus supplement, without service charge and upon payment of any taxes and other governmental charges as described in the Senior Indenture. Any transfer or exchange will be effected upon the Senior Trustee’s satisfaction with the documents of title and indemnity of the person making the request. (Sections 2.6 and 2.7 of the Senior Indenture.)

The Senior Trustee will not be required to exchange or register a transfer of any debt securities of a series selected, called or being called for redemption except, in the case of any debt security to be redeemed in part, the portion of that debt security not to be so redeemed. (Section 2.6 of the Senior Indenture.) See the information under the caption “Book-Entry System.”

Payment and Paying Agents

Principal, interest and premium, if any, on debt securities issued in the form of global securities will be paid in the manner described below under the caption “Book-Entry System.” Unless the prospectus supplement that describes a particular series of debt securities provides otherwise with respect to that series, interest on debt securities that are in the form of certificated securities will be paid by check mailed to the holder at that person’s address as it appears in the register for the debt securities maintained by the Senior Trustee; however, a holder of $10,000,000 or more of the debt securities having the same interest payment dates will be entitled to receive payments of interest by wire transfer, if appropriate wire transfer instructions have been received by the Senior Trustee on or prior to the applicable record date. (Section 2.12 of the Senior Indenture.) Unless the prospectus supplement that describes a particular series of debt securities provides otherwise with respect to that series, the principal, interest at maturity and premium, if any, on debt securities in the form of certificated securities will be payable in immediately available funds at the office of the Senior Trustee. (Section 2.12 of the Senior Indenture.)

All monies paid by us to a paying agent for the payment of principal, interest or premium on any debt security that remain unclaimed at the end of two years after that principal, interest or premium has become due and payable will be repaid to us, and the holder of that debt security will thereafter look only to us for payment of that principal, interest or premium. (Section 4.4 of the Senior Indenture.)

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Events of Default

The following constitute events of default under the Senior Indenture:

(Section 7.1 of the Senior Indenture.)

If an event of default occurs and is continuing, either the Senior Trustee or the holders of a majority in principal amount of the outstanding securities may declare the principal amount of all securities to be due and payable immediately. At any time after an acceleration of the securities has been declared, but before a judgment or decree of the immediate payment of the principal amount of the securities has been obtained, if we pay or deposit with the Senior Trustee a sum sufficient to pay all matured installments of interest and the principal and any premium that has become due otherwise than by acceleration and all defaults have been cured or waived, then that payment or deposit will cause an automatic rescission and annulment of the acceleration of the securities. (Section 7.1 of the Senior Indenture.)

The Senior Trustee generally will be under no obligation to exercise any of its rights or powers under the Senior Indenture at the request or direction of any of the holders unless such holders have offered acceptable indemnity to the Senior Trustee. (Section 8.2 of the Senior Indenture.) The holders of a majority in principal amount of the outstanding securities generally will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the Senior Trustee, or of exercising any trust or power conferred on the Senior Trustee, relating to the securities. (Section 7.7 of the Senior Indenture.) Each holder has the right to institute a proceeding relating to the Senior Indenture, but this right is subject to conditions precedent specified in the Senior Indenture. (Sections 7.4 and 7.7 of the Senior Indenture.) The Senior Trustee is required to give the holders of the securities notice of the occurrence of a default within 90 days of the default, unless the default is cured or waived. Except in the case of a payment default on any securities, however, the Senior Trustee may withhold notice if it determines in good faith that it is in the interest of holders to do so. (Section 7.8 of the Senior Indenture.) We are required to deliver to the Senior Trustee each year a certificate as to whether or not we are in compliance with the conditions and covenants under the Senior Indenture. (Section 5.5 of the Senior Indenture.)

Modification

We and the Senior Trustee may modify and amend the Senior Indenture from time to time.

We will not need the consent of the holders of the securities for the following types of amendments:

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(Section 12.1 of the Senior Indenture.)

We will need the consent of the holders of each outstanding security affected by a proposed amendment if the amendment would cause any of the following to occur:

Additionally, we may not modify these requirements or reduce the percentage of outstanding securities necessary to consent to the modification or amendment of the Senior Indenture or to waive past defaults without the consent of the holders of all of the outstanding debt securities.

Amendments requiring holders’ consent, other than those described in the above paragraph will require the approval of the holders of a majority in aggregate principal amount of the outstanding securities.

(Section 12.2 of the Senior Indenture.)

Defeasance and Discharge

We may be discharged from all obligations relating to the debt securities and the Senior Indenture (except for specified obligations such as obligations to register the transfer or exchange of securities, replace stolen, lost or mutilated securities and maintain paying agencies) if we irrevocably deposit with the Senior Trustee, in trust for the benefit of holders of securities, money or United States government obligations (or any combination thereof) sufficient to make all payments of principal, premium and interest on the securities on the dates those payments are due. To discharge these obligations, we must deliver to the Senior Trustee an opinion of counsel that the holders of the securities will not recognize income, gain or loss for federal income tax purposes as a result of the defeasance or discharge of the Senior Indenture. If we discharge our obligations as described above, the holders of securities must look only to the funds deposited with the Senior Trustee, and not us, for payments on the securities. (Section 4.1 of the Senior Indenture.)

Consolidation, Merger and Sale of Assets

We will not merge into any other corporation or sell or otherwise transfer all or substantially all our assets unless the successor or transferee corporation assumes by supplemental indenture our obligations to pay the principal, interest and premium on all of the securities and our obligation to perform every covenant of the Senior Indenture that we are to perform or observe and we or the successor or transferee corporation, as applicable, are not, immediately following such merger, sale or transfer, in default in the performance of any of those covenants. Upon any merger, sale or transfer of all or substantially all of our assets, the successor or transferee corporation will succeed to, and be substituted for, and may exercise all of our rights and powers under the Senior Indenture with the same effect as if the successor corporation had been named as us in the Senior Indenture, and we will be released from all obligations under the Senior Indenture. Unless the prospectus supplement that describes a particular series of debt securities provides otherwise with respect to that series, the Senior Indenture will define all or substantially all of our assets as being 50% or more of our total assets as shown on our balance sheet as of the end of the prior year and specifically will permit any sale, transfer or conveyance during a calendar year of less than 50% of our total assets without the consent of the holders of the securities. (Sections 11.1 and 11.2 of the Senior Indenture.)

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Resignation or Removal of Senior Trustee

The Senior Trustee may resign at any time by notifying us in writing and specifying the day upon which the resignation is to take effect. The resignation will not take effect, however, until a successor trustee has been appointed. (Section 8.10 of the Senior Indenture.)

The holders of a majority in principal amount of the outstanding securities may remove the Senior Trustee at any time. In addition, so long as no event of default or event that, with the giving of notice or lapse of time or both, would become an event of default has occurred and is continuing, we may remove the Senior Trustee upon notice to the holder of each security outstanding and appointment of a successor Senior Trustee. (Section 8.10 of the Senior Indenture.)

Concerning the Senior Trustee

Wells Fargo Bank, National Association is the Senior Trustee. We maintain banking relationships with the Senior Trustee in the ordinary course of business. The Senior Trustee also acts as trustee for securities of some of our affiliates.

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BOOK-ENTRY SYSTEM

Unless otherwise specified in the applicable prospectus supplement, each series of securities offered by this prospectus will be issued as fully-registered global securities representing all or part of that series of securities. This means that we will not issue certificates for that series of securities to the holders. Instead, a global security representing that series of securities will be deposited with, or on behalf of, DTC or its successor, as the depository. The global securities will be registered at the request of DTC in the name of Cede & Co., DTC’s nominee, or such other name as may be requested by an authorized representative of DTC.

DTC will keep an electronic record of its participants (for example, your broker) whose clients have purchased securities represented by a global security. Unless a global security is exchanged in whole or in part for a certificated security, a global security may not be transferred, except that DTC, its nominees and successors may transfer a global security as a whole to one another.

Beneficial interests in global securities will be shown on, and transfers of interests will be made only through, records maintained by DTC and its participants. The laws of some jurisdictions require that some purchasers take physical delivery of securities in definitive form. These laws may impair the ability to transfer beneficial interests in a global security.

We will make payments of principal, interest, if any, and premium, if any, to DTC or its nominee. We, the applicable trustee and any paying agent will treat DTC or its nominee as the owner of the global security for all purposes, including any notices and voting. Accordingly, neither we nor any trustee nor any paying agent will have any direct responsibility or liability to pay amounts due on a global security to owners of beneficial interests in a global security.

DTC is a limited-purpose trust company organized under the New York Banking Law, a “banking organization” within the meaning of the New York Banking Law, a member of the Federal Reserve System, a “clearing corporation” within the meaning of the New York Uniform Commercial Code and a “clearing agency” registered pursuant to the provisions of Section 17A of the Exchange Act. DTC holds securities that its participants, or “direct participants,” deposit with DTC. DTC also facilitates the post-trade settlement among direct participants of sales and other securities transactions in deposited securities through electronic computerized book-entry transfers and pledges between direct participants’ accounts. This eliminates the need for physical movement of securities certificates. Direct participants include both U.S. and non-U.S. securities brokers and dealers, banks, trust companies, clearing corporations and certain other organizations. DTC is a wholly owned subsidiary of The Depository Trust & Clearing Corporation, or “DTCC.” DTCC is the holding company for DTC, National Securities Clearing Corporation and Fixed Income Clearing Corporation, all of which are registered clearing agencies. DTCC is owned by the users of its regulated subsidiaries. Access to the DTC system is also available to others such as both U.S. and non-U.S. securities brokers and dealers, banks, trust companies and clearing corporations that clear through or maintain a custodial relationship with a direct participant either directly or indirectly, an “indirect participant.” Direct participants and indirect participants are referred to collectively as “participants.” The DTC Rules applicable to its participants are on file with the SEC.

Purchases of global securities under the DTC system must be made by or through direct participants, which will receive a credit for the securities on DTC’s records. The ownership interest of each actual purchaser of each security, or “beneficial owner,” is in turn to be recorded on the direct and indirect participants’ records. Beneficial owners will not receive written confirmation from DTC of their purchase. Beneficial owners are, however, expected to receive written confirmations providing details of the transaction, as well as periodic statements of their holdings, from the direct or indirect participant through which the beneficial owner entered into the transaction. Transfers of ownership interests in the global securities are to be accomplished by entries made on the books of direct and indirect participants acting on behalf of beneficial owners. Beneficial owners will not receive certificates representing their ownership interests in the global securities, except in the event that use of the book-entry system for the global securities is discontinued.

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To facilitate subsequent transfers, all securities deposited by direct participants with DTC are registered in the name of Cede & Co. or such other name as may be requested by an authorized representative of DTC. The deposit of securities with DTC and their registration in the name of Cede & Co. or such other nominee do not effect any change in beneficial ownership. DTC has no knowledge of the actual beneficial owners of the securities. DTC’s records reflect only the identity of the direct participants to whose accounts such securities are credited, which may or may not be the beneficial owners. The direct and indirect participants remain responsible for keeping account of their holdings on behalf of their customers.

Conveyance of notices and other communications by DTC to direct participants, by direct participants to indirect participants and by direct participants and indirect participants to beneficial owners will be governed by arrangements among them, subject to any statutory or regulatory requirements as may be in effect from time to time.

If a particular series of securities is redeemable at our option or at the option of the holder, redemption notices will be sent to DTC. If less than all of the securities of a series are being redeemed, DTC’s practice is to determine by lot the amount of the interest of each direct participant in such series to be redeemed. Redemption proceeds and distributions on global securities will be made to Cede & Co. or such other nominee as may be requested by an authorized representative of DTC. Upon DTC’s receipt of funds and corresponding detail information from us, any trustee or any paying agent, DTC’s practice is to credit direct participants’ accounts in accordance with the holdings information shown on DTC’s records on the payment date. Payments by participants to beneficial owners of securities will be governed by standing instructions and customary practices, as is the case with securities held for the accounts of customers in bearer form or registered in “street name.” Payments will be the responsibility of such participant and not of DTC nor its nominee, any trustee, any paying agent or us, subject to any statutory or regulatory requirements. Payment of redemption proceeds and distributions to Cede & Co. or such other nominee as may be requested by an authorized representative of DTC is the responsibility of us, the applicable trustee or the applicable paying agent, disbursement of such payments to direct participants will be the responsibility of DTC, and disbursement of such payments to the beneficial owners will be the responsibility of direct and indirect participants.

Neither DTC nor Cede & Co. or any other DTC nominee will consent or vote with respect to global securities unless authorized by a direct participant in accordance with DTC’s procedures. Under its usual procedures, DTC mails an omnibus proxy to us as soon as possible after the record date. The omnibus proxy assigns Cede & Co.’s consenting or voting rights to those direct participants to whose accounts the securities are credited on the record date as identified in a listing attached to the omnibus proxy.

Global securities will be exchangeable for corresponding certificated securities registered in the name of persons other than DTC or its nominee if (1) DTC (a) notifies us that it is unwilling or unable to continue as depository for any of the global securities or (b) at any time ceases to be a clearing agency registered under the Exchange Act, (2) an event of default occurs and is continuing with respect to the applicable series of securities or (3) we execute and deliver to the applicable trustee an order that the global securities will be so exchangeable.

The information in this section concerning DTC and DTC’s book-entry system has been obtained from DTC, and we and any underwriters, dealers or agents are not responsible for the accuracy of the information or for the performance by DTC of its obligations under the rules and procedures governing its operations or otherwise.

Any underwriters, dealers or agents of any securities may be direct participants of DTC.

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PLAN OF DISTRIBUTION

We may sell the securities offered under this prospectus through underwriters or dealers, through agents or directly to one or more purchasers. The terms under which the securities are offered and the method of distribution will be set forth in the applicable prospectus supplement.

Underwriters, dealers and agents that participate in the distribution of the securities offered under this prospectus may be underwriters as defined in the Securities Act of 1933, as amended, the “Securities Act,” and any discounts or commissions received by them from us and any profit on the resale of the offered securities by them may be treated as underwriting discounts and commissions under the Securities Act. Any underwriters or agents will be identified and their compensation, including any underwriting discount or commission, will be described in the applicable prospectus supplement. The applicable prospectus supplement will also describe other terms of the offering, including the initial public offering price and any discounts or concessions allowed or reallowed to dealers.

The distribution of the securities described in this prospectus may be effected from time to time in one or more transactions at a fixed price or prices, which may be changed, at market prices prevailing at the time of sale, at prices related to the prevailing market prices or at negotiated prices.

We may determine the price or other terms of the securities offered under this prospectus by use of an electronic auction. We will describe in the applicable prospectus supplement how any auction will be conducted to determine the price or any other terms of the securities, how potential investors may participate in the auction and, where applicable, the nature of the underwriters’ obligations with respect to the auction.

Each series of securities will be a new issue of securities and will have no established trading market. Any underwriters to whom securities are sold for public offering and sale may make a market in such securities, but such underwriters will not be obligated to do so and may discontinue any market making at any time without notice. The securities may or may not be listed on a national securities exchange.

Under agreements into which we may enter in connection with the sale of the securities, underwriters, dealers and agents who participate in the distribution of the securities may be entitled to indemnification by us against specified liabilities, including liabilities under the Securities Act.

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LEGAL OPINIONS

Unless otherwise indicated in the applicable prospectus supplement, legal opinions relating to the validity of the securities being offered by this prospectus and certain other matters will be rendered by our counsel, Scott M. Wilensky, 414 Nicollet Mall, Minneapolis, Minnesota, and Jones Day, Chicago, Illinois, counsel for our company. Unless otherwise indicated in the prospectus supplement relating to a particular series of securities, certain legal matters will be passed upon for the underwriters, dealers or agents named in a prospectus supplement by Hunton Andrews Kurth LLP, New York, New York. Scott M. Wilensky is our Executive Vice President and General Counsel and is the beneficial owner of less than 1% of the common stock of our parent company, Xcel Energy Inc.

EXPERTS

The consolidated financial statements, and the related financial statement schedule, incorporated in this prospectus by reference from Northern States Power Company’s, a Minnesota corporation, Annual Report on Form 10-K have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their report, which is incorporated herein by reference. Such consolidated financial statements and financial statement schedule have been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

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PROSPECTUS

NORTHERN STATES POWER COMPANY

1414 W. Hamilton Avenue

Eau Claire, Wisconsin 54701

(715) 737-2625

FIRST MORTGAGE BONDS

SENIOR UNSECURED DEBT SECURITIES

We may offer and sell from time to time, in one or more offerings, together or separately, any combination of the securities listed above and described in this prospectus. We may offer and sell these securities to or through one or more underwriters, dealers and/or agents, or directly to purchasers, on a continuous or delayed basis.

This prospectus describes some of the general terms that may apply to the securities and the general manner in which they may be offered. The specific terms of any securities to be offered, and the specific manner in which they may be offered, will be described in a supplement to this prospectus. This prospectus may not be used to sell securities unless accompanied by a prospectus supplement.

You should carefully consider the risk factors set forth in the applicable prospectus supplement and certain of our filings with the Securities and Exchange Commission before making any decision to invest in any of the securities described in this prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is April 18, 2018.

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ABOUT THIS PROSPECTUS

This document is called a “prospectus” and it provides you with a general description of the securities we may offer. Each time we sell securities under this prospectus, we will provide a prospectus supplement containing specific information about the terms of the securities being offered. That prospectus supplement may include a discussion of any risk factors or other special considerations that apply to those securities. The prospectus supplement may also add, update or change the information in this prospectus. If there is any inconsistency between the information in this prospectus and in the prospectus supplement, you should rely on the information in the prospectus supplement. You should read this prospectus and the applicable prospectus supplement together with the additional information described under the caption “Where You Can Find More Information.” We may also prepare free writing prospectuses that describe particular securities. Any free writing prospectus should also be read in connection with this prospectus and with the prospectus supplement referred to therein. For purposes of this prospectus, any reference to an applicable prospectus supplement may also refer to a free writing prospectus, unless the context otherwise requires.

This prospectus is part of a registration statement that we filed with the Securities and Exchange Commission, or the “SEC,” using a shelf registration process. As permitted by SEC rules, this prospectus does not contain all of the information included in the registration statement and the accompanying exhibits and schedules we filed with the SEC. You should read the registration statement and the related exhibits and schedules for more information about us and our securities. The registration statement and the related exhibits and schedules can be read at the SEC’s website or at the SEC’s offices. The SEC’s website and street addresses are provided under the caption “Where You Can Find More Information.”

The distribution of this prospectus and the applicable prospectus supplement and the offering of the securities in certain jurisdictions may be restricted by law. Persons into whose possession this prospectus and the applicable prospectus supplement come should inform themselves about and observe any such restrictions. This prospectus and the applicable prospectus supplement do not constitute, and may not be used in connection with, an offer or solicitation by anyone in any jurisdiction in which such offer or solicitation is not authorized or in which the person making such offering or solicitation is not qualified to do so or to any person to whom it is unlawful to make such offer or solicitation.

This prospectus, the applicable prospectus supplement and any free writing prospectus that we prepare or authorize contain and incorporate by reference information that you should consider when making your investment decision. No one is authorized to provide you with information different from that which is contained, or deemed to be contained, in this prospectus and applicable prospectus supplement. We are not making an offer of these securities in any jurisdiction where the offer is not permitted. You should not assume that the information in this prospectus or the documents incorporated by reference is accurate as of any date other than the date on the front of those documents.

Unless otherwise specified or unless the context requires otherwise, all references in this prospectus to “Northern States Power Company,” “NSP,” “we,” “us,” “our,” “the Company,” or similar terms refer to Northern States Power Company.

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WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and current reports and other information with the SEC. Our SEC filings are available to the public on the SEC’s website at http://www.sec.gov. You may also read and copy any document we file with the SEC at the SEC’s Public Reference Room located at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information on the Public Reference Room.

The SEC allows us to “incorporate by reference” the information we file with it, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is an important part of this prospectus, and information that we file later with the SEC will automatically update and supersede this information. We incorporate by reference our Annual Report on Form 10-K for the year ended December 31, 2017, including information specifically incorporated by reference into our Form 10-K from Xcel Energy Inc.’s definitive Proxy Statement for its 2018 Annual Meeting of Shareholders, and any future filings made with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, or the Exchange Act, from the date of the prospectus until we sell all of the securities (other than, in each case, documents or information deemed to have been furnished and not filed in accordance with SEC rules).

We will provide, without charge, to each person, including any beneficial owner of our securities to whom this prospectus is delivered, upon written or oral request, a copy of any or all documents referred to above that have been incorporated by reference into this prospectus, excluding exhibits to those documents unless they are specifically incorporated by reference into those documents. You may request these documents from:

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OUR COMPANY

We were incorporated in 1901 under the laws of the State of Wisconsin. We are a utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of northwestern Wisconsin and in the western portion of the Upper Peninsula of Michigan. We also purchase, transport, distribute and sell natural gas to retail customers and transport customer-owned natural gas in the same service territory. As of December 31, 2017, we provided electric utility service to approximately 259,000 customers and natural gas utility service to approximately 114,000 customers.

Our electric production and transmission system is managed as an integrated system with that of Northern States Power Company, a Minnesota corporation, or “NSP-Minnesota”, jointly referred to as the NSP System. The electric production and transmission costs of the entire NSP System are shared by us and NSP-Minnesota. A Federal Energy Regulatory Commission-approved agreement between the two companies, called the Interchange Agreement, provides for the sharing of all generation and transmission costs of the NSP System. Such costs include current and potential obligations of NSP-Minnesota related to its nuclear generating facilities.

We own the following direct subsidiaries: Chippewa and Flambeau Improvement Co., which operates hydro reservoirs; Clearwater Investments Inc., which owns interests in affordable housing; and NSP Lands, Inc., which holds real estate.

Our principal executive offices are located at 1414 W. Hamilton Avenue, Eau Claire, Wisconsin 54701, and our telephone number is (715) 839-2625.

DESCRIPTION OF THE FIRST MORTGAGE BONDS

The description below contains a summary of selected provisions of the indenture, including supplemental indentures, under which the first mortgage bonds will be issued. This summary is not complete. The indenture and the form of supplemental indenture applicable to the first mortgage bonds have been filed as exhibits to the registration statement of which this prospectus constitutes a part. You should read them for provisions that may be important to you. In the summary below, we have included references to section numbers of the indenture so that you can easily locate these provisions.

We are not required to issue future issues of indebtedness under the indenture described below. We are free to use other indentures or documentation, containing provisions different from those described in this prospectus, in connection with future issues of other indebtedness not issued under this prospectus.

The first mortgage bonds will be represented either by global securities registered in the name of The Depository Trust Company, or DTC, as depository, or Depository, or its nominee, or by securities in certificated form issued to the registered owners, as set forth in the applicable prospectus supplement. See the information under the caption “Book-Entry System” in this prospectus.

General

We may issue the first mortgage bonds from time to time in one or more new series under the Supplemental and Restated Trust Indenture dated March 1, 1991, which we refer to as the Restated Indenture, as previously supplemented by nine supplemental trust indentures and as to be supplemented by one or more new supplemental indentures for the first mortgage bonds, which we collectively refer to as the Mortgage Indenture, all from us to U.S. Bank National Association, as successor trustee, which we refer to as the Mortgage Trustee. The Mortgage Indenture will govern the first mortgage bonds offered by this prospectus. As of December 31, 2017, there were five series of first mortgage bonds in an aggregate principal amount of $750 million outstanding under the Mortgage Indenture.

The holders of the outstanding first mortgage bonds do not, and, unless the prospectus supplement that describes a particular series of first mortgage bonds provides otherwise with respect to that series, the holders of any first mortgage bonds offered by this prospectus will not, have the right to require us to repurchase the first mortgage bonds if we become involved in a highly leveraged or change in control transaction. The Mortgage Indenture does not have any provision that is designed specifically in response to highly leveraged or change in control transactions.

When we offer to sell a particular series of first mortgage bonds, we will describe the specific terms of that series in a prospectus supplement relating to that series, including the following terms:

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Unless the prospectus supplement that describes a particular series of first mortgage bonds provides otherwise, we may from time to time, without the consent of the holders of that series of first mortgage bonds, reopen such series of first mortgage bonds and issue additional first mortgage bonds with the same terms (including maturity and interest payment terms) as such series of first mortgage bonds.

Interest Payments

Unless the prospectus supplement that describes a particular series of first mortgage bonds provides otherwise, the amount of interest payable will be computed on the basis of a 360-day year of twelve 30-day months. In the event that any date on which such interest is payable on the first mortgage bonds is not a business day, then payment of the interest payable on such date will be made on the next succeeding day which is a business day (and without any interest or other payment in respect of any such delay), with the same force and effect as if made on such date.

Redemption

The prospectus supplement that describes a particular series of first mortgage bonds will set forth any terms for the optional or mandatory redemption of that particular series.

Security for the First Mortgage Bonds

The first mortgage bonds being issued pursuant to this prospectus will be secured equally and ratably with all of our other outstanding first mortgage bonds, subject to the provisions relating to any sinking fund for any particular series of first mortgage bonds, by a valid and direct first mortgage lien on all of the real and fixed properties, leasehold rights, franchises and permits then owned by us subject only to permitted encumbrances (as discussed below). The lien of the Mortgage Indenture does not cover securities, cash, contracts, receivables, motor vehicles, merchandise, equipment and supplies and specified non-utility property.

The Mortgage Indenture subjects to the lien of the Mortgage Indenture all of our property, rights and franchises, except as otherwise expressly provided. These provisions might not be effective as to property acquired within 90 days prior and subsequent to the filing of a case by us under the U.S. Bankruptcy Code.

We have not made any appraisal of the properties subject to the lien of the Mortgage Indenture. The value of the properties in the event of liquidation will depend on market and economic conditions, the availability of buyers and other factors.

The Mortgage Indenture provides that no liens prior or equal to the lien of the Mortgage Indenture, other than permitted encumbrances, may be created or permitted to exist on the mortgaged and pledged property whether now owned or acquired in the future. (Section 8.04 of the Restated Indenture.)

Permitted encumbrances include, among others, the following:

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(Section 1.03 of the Restated Indenture.)

With the consent of the holders of 66 2/3% of the principal amount of first mortgage bonds outstanding, the Company may (1) permit the creation or existence of a prior lien with respect to up to 50% of the sum of our depreciable property and land, after giving effect to the prior lien and the acquisition of the property subject to the prior lien or (2) terminate the lien of the Mortgage Indenture with respect to up to 50% of the sum of our depreciable property and land. (Section 19.02(e) of the Restated Indenture.)

Sinking Fund Provisions

We currently do not have any outstanding first mortgage bonds that are, and, unless the prospectus supplement that describes a particular series of first mortgage bonds provides otherwise with respect to that series, the first mortgage bonds offered by this prospectus will not be, subject to a sinking fund.

Maintenance Provisions

As a maintenance fund for the first mortgage bonds, we have agreed to pay to the Mortgage Trustee on each May 1 an amount equal to 2.50% of our completed depreciable property as of the end of the preceding calendar year, after deducting credits at our option for the following:

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(Section 9.01 of the Restated Indenture.)

We may withdraw moneys from the maintenance fund in amounts equal to retirements of first mortgage bonds and permanent additions. Cash on deposit in the maintenance fund may be used for the purchase or redemption of first mortgage bonds. Any redemption of this nature would be at the applicable regular redemption price of the first mortgage bonds to be redeemed and subject to any restrictions on the redemption of the first mortgage bonds. (Sections 9.03 and 9.04 of the Restated Indenture).

The Restated Indenture further provides that to the extent that maintenance fund credits exceed 2.50% of our completed depreciable property for any year after 1990, such excess credits may be applied in future years (1) to offset any maintenance fund deficiency or (2) to increase the amount of established permanent additions available for use under the Mortgage Indenture in an aggregate amount equal to the lesser of such excess credits or the amount of permanent additions used after 1990 for the maintenance fund. (Section 9.05 of the Restated Indenture.)

We have agreed to maintain our properties in adequate repair, working order and condition. (Section 8.06 of the Restated Indenture.)

Issuance of Additional First Mortgage Bonds

The maximum principal amount of first mortgage bonds that we may issue under the Mortgage Indenture is not limited, except as described below. We may issue additional first mortgage bonds in an aggregate principal amount not exceeding (1) 66 2/3% of the cost or fair value, whichever is less, of permanent additions after deducting retirements (Article V of the Restated Indenture); (2) the aggregate principal amount of retired first mortgage bonds, which have not been otherwise used under the Mortgage Indenture (Article VI of the Restated Indenture); or (3) the amount of cash deposited with the Mortgage Trustee, which cash may be withdrawn on the same basis as additional first mortgage bonds may be issued under clauses (1) and (2) above (Article VII of the Restated Indenture).

At December 31, 2017, the amount of net permanent additions available for the issuance of first mortgage bonds was approximately $1.767 billion, which could be used to authenticate up to approximately $1.178 billion principal amount of the first mortgage bonds. As of December 31, 2017, $11.000 million of retired first mortgage bonds were available to authenticate up to $11.000 million of first mortgage bonds.

We may not issue any additional first mortgage bonds on the basis of clause (1), clause (2) under specified conditions or clause (3) above, unless the earnings applicable to bond interest for a specified 12-month period are equal to at least twice the annual interest requirements on the first mortgage bonds, including those about to be issued, any permitted indebtedness and any obligations secured by prior liens. (Sections 1.03, 5.03, 5.06, 6.02 and 7.01 of the Restated Indenture.) The calculation of earnings applicable to bond interest includes all of our gross revenue, including our nonutility revenues. (Section 1.03 of the Restated Indenture.)

Permanent additions generally include, among other things, the following:

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(Section 1.03 of the Restated Indenture.)

Earnings applicable to bond interest for the 12 months ended December 31, 2017 would be 4.30 times the annual interest requirements on our first mortgage bonds and any obligations secured by prior liens and any permitted indebtedness secured by permitted encumbrances. Additional first mortgage bonds may vary as to maturity, interest rate, redemption prices and sinking fund provisions, among other things. (Article II of the Restated Indenture.)

Provisions Limiting Dividends on Common Stock

The Mortgage Indenture does not restrict our ability to pay dividends on our common stock.

Release Provisions

The Mortgage Indenture permits the release from its lien of any property upon depositing or pledging cash or certain other property of comparable fair value. The Mortgage Indenture also permits the following, in each case without any release or consent by the Mortgage Trustee or accountability to the Mortgage Trustee for any consideration received by us:

(Article XI of the Restated Indenture.)

Any of the mortgaged and pledged property may be released from the lien of the Mortgage Indenture if, after the release, the fair value of the remaining mortgaged and pledged property of the character of permanent additions equals or exceeds a sum equal to 150% of the aggregate principal amount of first mortgage bonds outstanding. (Section 11.03(k) of the Restated Indenture.) Upon satisfaction of the requirements set forth in the Mortgage Indenture, this provision would permit us to spin off or otherwise dispose of a substantial amount of assets or a line of business, including all or a portion of our electric generation, transmission or distribution assets, or our gas storage and distribution assets, without depositing cash or property with the Mortgage Trustee or obtaining the consent of the holders of the first mortgage bonds.

Modification of the Mortgage Indenture

We and the Mortgage Trustee may modify and amend the Mortgage Indenture from time to time. We will not need the consent of the holders of the first mortgage bonds for the following types of amendments, among others:

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(Section 19.01 of the Restated Indenture.)

With our consent, other provisions of the Mortgage Indenture may be changed by the affirmative vote of the holders of 66 2/3% in principal amount of the first mortgage bonds outstanding except that, among other things, the following may not be done without the consent of the holder of each first mortgage bond so affected:

(Section 19.02 of the Restated Indenture.)

Defaults

The following is a summary of events defined in the Mortgage Indenture as completed defaults:

(Section 14.01 of the Restated Indenture.)

Notice of Default. The Mortgage Trustee is required to give notice to bondholders within 90 days after the occurrence of a default, unless the default has been cured or waived before giving its notice; provided that, except in the case of a default in payment of principal or interest on any first mortgage bond or to make any sinking fund payment, the Mortgage Trustee may withhold the notice if it determines in good faith that withholding the notice is in the interest of the bondholders. Any notice of default of the covenants contained in Section 8.11 of the Restated Indenture regarding bankruptcy, insolvency, assignment or receivership may not be given until at least 90 days after the occurrence of the default. (Section 17.02 of the Restated Indenture.)

Acceleration of Maturity. In case of a completed default, the Mortgage Trustee may, and upon request of the holders of 25% in principal amount of the first mortgage bonds outstanding will, declare the first mortgage bonds due and payable, subject to the right of the holders of a majority of the first mortgage bonds then-outstanding to rescind or annul such action. Further, the Mortgage Trustee is obligated to take the actions provided in the Mortgage Indenture to enforce payment of the first mortgage bonds and the lien of the Mortgage Indenture upon being requested to do so by the holders of a majority in principal amount of the first mortgage bonds. However, the holders of a majority in principal amount of the first mortgage bonds may direct the taking

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of any of these actions or the refraining from these actions as is not in violation of the law or the Mortgage Indenture. Before taking these actions, the Mortgage Trustee may require adequate indemnity against the costs, expenses and liabilities to be incurred in connection with these actions. (Article XIV of the Restated Indenture.)

Compliance Certificate. We are required to furnish with the Mortgage Trustee information, documents and reports regarding our compliance with the conditions and covenants of the Mortgage Indenture as may be required by the rules and regulations of the SEC, including a certificate, furnished at least annually, as to whether, to the knowledge of the officer signing such certificate, we are in compliance with the conditions and covenants under the Mortgage Indenture. (Section 8.18 of the Restated Indenture.)

Other Provisions

Whenever all indebtedness secured by the Mortgage Indenture has been paid, or adequate provision for payment has been made, the Mortgage Trustee will cancel and discharge the Mortgage Indenture. (Article XVIII of the Restated Indenture.) We may deposit with the Mortgage Trustee any combination of cash or government obligations in order to provide for the payment of any series or all of the first mortgage bonds outstanding. This deposit could constitute a taxable event as to holders of those first mortgage bonds, creating possible adverse tax consequences. The Mortgage Indenture also provides that we must furnish to the Mortgage Trustee officers’ certificates, certificates of an engineer, appraiser or other expert and, in some cases, accountants’ certificates in connection with the authentication of first mortgage bonds, the release or release and substitution of property and some other matters, and opinions of counsel as to the lien of the Mortgage Indenture and some other matters. (Articles IV, V, VI, VII, XI and XVIII and Section 21.08 of the Restated Indenture.)

Concerning the Trustee

U.S. Bank National Association is the Mortgage Trustee under the Mortgage Indenture. We maintain banking relationships with the Mortgage Trustee in the ordinary course of business. The Mortgage Trustee also acts as trustee for our senior unsecured debt securities discussed below under “Description of the Senior Unsecured Debt Securities.”

Governing Law

The Mortgage Indenture and first mortgage bonds to be issued pursuant to this prospectus are governed by, and construed in accordance with, the laws of the State of Wisconsin.

DESCRIPTION OF THE SENIOR UNSECURED DEBT SECURITIES

The description below contains a summary of selected provisions of the indenture, including supplemental indentures, under which the senior unsecured debt securities, which we refer to as debt securities, will be issued. This summary is not complete. The indenture and the form of supplemental indenture applicable to the debt securities have been filed as exhibits to the registration statement of which this prospectus is a part. You should read them for provisions that may be important to you. In the summary below, we have included references to section numbers of the indenture so that you can easily locate these provisions.

We are not required to issue future issues of indebtedness under the indenture described below. We are free to use other indentures or documentation, containing provisions different from those described in this prospectus, in connection with future issues of other indebtedness not issued under this prospectus.

The debt securities will be represented either by global securities registered in the name of DTC, as Depository, or its nominee, or by securities in certificated form issued to the registered owners, as set forth in the applicable prospectus supplement. See the information under the caption “Book-Entry System” in this prospectus.

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General

We may issue the debt securities from time to time in one or more new series under the Indenture dated September 1, 2000, as previously supplemented by one supplemental indenture and as to be supplemented by one or more new supplemental indentures for the debt securities, which we collectively refer to as the Senior Indenture, all from us to U.S. Bank National Association, as successor trustee, which we refer to as the Senior Trustee. The Senior Indenture will govern the debt securities offered by this prospectus. As of December 31, 2017, there were no debt securities outstanding under the Senior Indenture.

The holders of the outstanding debt securities do not, and, unless the supplemental indenture that describes a particular series of debt securities provides otherwise with respect to that series, the holders of any debt securities offered by this prospectus will not, have the right to require us to repurchase the debt securities if we become involved in a highly leveraged or change in control transaction. The Senior Indenture does not have any provision that is designed specifically in response to highly leveraged or change in control transactions.

The debt securities will be our senior unsecured obligations and will rank on a parity with our other existing and future senior unsecured indebtedness. Our secured debt will have a prior claim on the assets pledged to secure such debt and, therefore, our debt securities will be effectively subordinated to all of our current and future secured debt, including our first mortgage bonds to the extent of the value of the properties securing them. As of December 31, 2017, we had $750 million of secured debt outstanding. The amount of debt securities that we may issue under the Senior Indenture is not limited.

When we offer to sell a particular series of debt securities, we will describe the specific terms of that series in a prospectus supplement relating to that series, including the following terms:

Unless the prospectus supplement that describes a particular series of debt securities provides otherwise, we may from time to time, without the consent of the holders of that series of debt securities, reopen such series and issue additional debt securities with the same terms (including maturity and interest payment terms) as such series of debt securities.

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Interest Payments

Unless the prospectus supplement that describes a particular series of debt securities provides otherwise, the amount of interest payable will be computed on the basis of a 360-day year of twelve 30-day months. In the event that any date on which such interest is payable on the debt securities is not a business day, then payment of the interest payable on such date will be made on the next succeeding day which is a business day (and without any interest or other payment in respect of any such delay), with the same force and effect as if made on such date.

Registration, Transfer and Exchange

Debt securities of any series may be exchanged for one or more new securities of any authorized denomination and of like aggregate principal amount, series and stated maturity and having the same terms and issue date or dates. (Section 2.6 of the Senior Indenture).

Unless the prospectus supplement that describes a particular series of debt securities provides otherwise with respect to that series, debt securities may be presented for registration of transfer (duly endorsed or accompanied by a duly executed written instrument of transfer) at the office of the Senior Trustee maintained for that purpose and referred to in the applicable prospectus supplement, without service charge and upon payment of any taxes and other governmental charges as described in the Senior Indenture. Any transfer or exchange will be effected upon the Senior Trustee’s satisfaction with the documents of title and indemnity of the person making the request. (Sections 2.6 and 2.7 of the Senior Indenture.)

The Senior Trustee will not be required to exchange or register a transfer of any debt securities of a series selected, called or being called for redemption except, in the case of any debt security to be redeemed in part, the portion of that debt security not to be so redeemed. (Section 2.6 of the Senior Indenture.) See the information under the caption “Book-Entry System.”

Payment and Paying Agents

Principal, interest and premium, if any, on debt securities issued in the form of global securities will be paid in the manner described below under the caption “Book-Entry System.” Unless the prospectus supplement that describes a particular series of debt securities provides otherwise with respect to that series, principal, interest and premium, if any, on debt securities that are in the form of certificated securities will be paid by check mailed to the holder at that person’s address as it appears in the register for the debt securities maintained by the Senior Trustee; however, a holder of $10,000,000 or more of the debt securities having the same interest payment dates will be entitled to receive payments of interest by wire transfer, if appropriate wire transfer instructions have been received by the Senior Trustee on or prior to the applicable record date. Unless the prospectus supplement that describes a particular series of debt securities provides otherwise with respect to that series, the principal, interest at maturity and premium, if any, on debt securities in the form of certificated securities will be payable in immediately available funds at the office of the Senior Trustee. (Section 2.12 of the Senior Indenture.)

All monies paid by us to a paying agent for the payment of principal, interest or premium, if any, on any debt securities that remain unclaimed at the end of two years after that principal, interest or premium has become due and payable will be repaid to us, and the holder of those debt securities will thereafter look only to us for payment of that principal, interest or premium. (Section 4.4 of the Senior Indenture.)

Events of Default

The following is a summary of events that constitute events of default under the Senior Indenture:

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(Section 7.1 of the Senior Indenture.)

If an event of default occurs and is continuing, either the Senior Trustee or the holders of a majority in principal amount of the outstanding debt securities may declare the principal amount of all debt securities to be due and payable immediately. At any time after an acceleration of the debt securities has been declared, but before a judgment or decree of the immediate payment of the principal amount of the debt securities has been obtained, if we pay or deposit with the Senior Trustee a sum sufficient to pay all matured installments of interest and the principal and any premium that has become due otherwise than by acceleration and all defaults have been cured or waived, then that payment or deposit will cause an automatic rescission and annulment of the acceleration of the debt securities. (Section 7.1 of the Senior Indenture.)

The Senior Trustee generally will be under no obligation to exercise any of its rights or powers under the Senior Indenture at the request or direction of any of the holders of debt securities unless such holders have offered reasonable indemnity to the Senior Trustee. (Section 8.2 of the Senior Indenture.) The holders of a majority in principal amount of the outstanding debt securities generally will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the Senior Trustee, or of exercising any trust or power conferred on the Senior Trustee, relating to the debt securities. (Section 7.7 of the Senior Indenture.) Each holder of a debt security has the right to institute a proceeding relating to the Senior Indenture, but this right is subject to conditions precedent specified in the Senior Indenture. (Section 7.4 and 7.7 of the Senior Indenture.) The Senior Trustee is required to give the holders of the debt securities notice of the occurrence of a default within 90 days of the occurrence of the default, unless the default is cured. Except in the case of a payment default on any debt securities, however, the Senior Trustee may withhold notice if it determines in good faith that it is in the interest of such holders to do so. (Section 7.8 of the Senior Indenture.) We are required to deliver to the Senior Trustee each year a certificate as to whether, to the knowledge of the officers signing such certificate, we are in compliance with the conditions and covenants under the Senior Indenture. (Section 5.5 of the Senior Indenture.)

Modification

We and the Senior Trustee may modify and amend the Senior Indenture from time to time.

We will not need the consent of the holders of debt securities for the following types of amendments, among others:

(Section 12.1 of the Senior Indenture.)

We will need the consent of the holders of each debt security so affected to do any of the following, among others:

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Additionally, we may not modify these requirements or reduce the percentage of outstanding securities necessary to consent to the modification or amendment of the Senior Indenture or to waive past defaults without the consent of the holders of all of the outstanding debt securities.

(Section 12.2 of the Senior Indenture.)

Amendments requiring holders’ consent, other than those described in the above paragraph, will require the approval of the holders of a majority in aggregate principal amount of the outstanding securities. (Section 12.2 of the Senior Indenture.)

Defeasance and Discharge

We may be discharged from all obligations relating to the debt securities and the Senior Indenture (except for specified obligations such as obligations to register the transfer or exchange of debt securities, replace stolen, lost or mutilated debt securities and maintain paying agencies) if we irrevocably deposit with the Senior Trustee, in trust for the benefit of holders of debt securities, cash or U.S. government obligations (or any combination thereof) sufficient to make all payments of principal, premium, if any, and interest on all outstanding debt securities on the dates those payments are due. To discharge these obligations, we must deliver to the Senior Trustee an opinion of counsel that the holders of the debt securities will not recognize income, gain or loss for federal income tax purposes as a result of the defeasance or discharge of the Senior Indenture. If we discharge our obligations as described above, the holders of debt securities must look only to the funds deposited with the Senior Trustee, and not us, for payments on the debt securities. (Section 4.1 of the Senior Indenture.)

Consolidation, Merger and Sale of Assets; No Financial Covenants

We will not merge into any other corporation or sell or otherwise transfer all or substantially all of our assets unless (1) the successor or transferee corporation assumes by supplemental indenture our obligations to pay the principal, interest and premium, if any, on all of the debt securities and our obligation to perform every covenant of the Senior Indenture that we are to perform or observe and (2) we or the successor or transferee corporation, as applicable, are not, immediately following such merger, sale or transfer, in default in the performance of any of those covenants. Upon any merger, sale or transfer of all or substantially all of our assets, the successor or transferee corporation will succeed to, and be substituted for, and may exercise all of our rights and powers under the Senior Indenture with the same effect as if the successor corporation had been named as us in the Senior Indenture, and we will be released from all obligations under the Senior Indenture. Unless the prospectus supplement that describes a particular series of debt securities provides otherwise with respect to that series, the Senior Indenture will define all or substantially all of our assets as being 50% or more of our total assets as shown on our balance sheet as of the end of the prior calendar year and specifically will permit any sale, transfer or disposition during a calendar year of less than 50% of our total assets without the consent of the holders of the securities. (Sections 11.1 and 11.2 of the Senior Indenture.)

Unless the prospectus supplement that describes a particular series of debt securities provides otherwise with respect to that series, the Senior Indenture will not contain any financial or other similar restrictive covenants.

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Resignation or Removal of Senior Trustee

The Senior Trustee may resign at any time by notifying us in writing and specifying the day upon which the resignation is to take effect. The resignation will not take effect, however, until a successor trustee has been appointed. (Section 8.10 of the Senior Indenture.)

The holders of a majority in principal amount of the outstanding securities may remove the Senior Trustee at any time. In addition, so long as no event of default or event that, with the giving of notice or lapse of time or both, would become an event of default has occurred and is continuing, we may remove the Senior Trustee upon notice to the holder of each debt security outstanding and appointment of a successor Senior Trustee. (Section 8.10 of the Senior Indenture.)

Concerning the Senior Trustee

U.S. Bank National Association is the Senior Trustee. We maintain banking relationships with the Senior Trustee in the ordinary course of business. The Senior Trustee also acts as trustee for our first mortgage bonds discussed above under “Description of the First Mortgage Bonds.”

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BOOK-ENTRY SYSTEM

Unless otherwise specified in the applicable prospectus supplement, each series of securities offered by this prospectus will be issued as fully-registered global securities representing all or part of that series of securities. This means that we will not issue certificates for that series of securities to the holders. Instead, a global security representing that series of securities will be deposited with, or on behalf of, DTC or its successor, as the depository. The global securities will be registered at the request of DTC in the name of Cede & Co., DTC’s nominee, or such other name as may be requested by an authorized representative of DTC.

DTC will keep an electronic record of its participants (for example, your broker) whose clients have purchased securities represented by a global security. Unless a global security is exchanged in whole or in part for a certificated security, a global security may not be transferred, except that DTC, its nominees and successors may transfer a global security as a whole to one another.

Beneficial interests in global securities will be shown on, and transfers of interests will be made only through, records maintained by DTC and its participants. The laws of some jurisdictions require that some purchasers take physical delivery of securities in definitive form. These laws may impair the ability to transfer beneficial interests in a global security.

We will make payments of principal, interest, if any, and premium, if any, to DTC or its nominee. We, the applicable trustee and any paying agent will treat DTC or its nominee as the owner of the global security for all purposes, including any notices and voting. Accordingly, neither we nor any trustee nor any paying agent will have any direct responsibility or liability to pay amounts due on a global security to owners of beneficial interests in a global security.

DTC is a limited-purpose trust company organized under the New York Banking Law, a “banking organization” within the meaning of the New York Banking Law, a member of the Federal Reserve System, a “clearing corporation” within the meaning of the New York Uniform Commercial Code and a “clearing agency” registered pursuant to the provisions of Section 17A of the Exchange Act. DTC holds securities that its participants, or “direct participants,” deposit with DTC. DTC also facilitates the post-trade settlement among direct participants of sales and other securities transactions in deposited securities through electronic computerized book-entry transfers and pledges between direct participants’ accounts. This eliminates the need for physical movement of securities certificates. Direct participants include both U.S. and non-U.S. securities brokers and dealers, banks, trust companies, clearing corporations and certain other organizations. DTC is a wholly owned subsidiary of The Depository Trust & Clearing Corporation, or “DTCC.” DTCC is the holding company for DTC, National Securities Clearing Corporation and Fixed Income Clearing Corporation, all of which are registered clearing agencies. DTCC is owned by the users of its regulated subsidiaries. Access to the DTC system is also available to others such as both U.S. and non-U.S. securities brokers and dealers, banks, trust companies and clearing corporations that clear through or maintain a custodial relationship with a direct participant either directly or indirectly, an “indirect participant.” Direct participants and indirect participants are referred to collectively as “participants.” The DTC Rules applicable to its participants are on file with the SEC.

Purchases of global securities under the DTC system must be made by or through direct participants, which will receive a credit for the securities on DTC’s records. The ownership interest of each actual purchaser of each security, or “beneficial owner,” is in turn to be recorded on the direct and indirect participants’ records. Beneficial owners will not receive written confirmation from DTC of their purchase. Beneficial owners are, however, expected to receive written confirmations providing details of the transaction, as well as periodic statements of their holdings, from the direct or indirect participant through which the beneficial owner entered into the transaction. Transfers of ownership interests in the global securities are to be accomplished by entries made on the books of direct and indirect participants acting on behalf of beneficial owners. Beneficial owners will not receive certificates representing their ownership interests in the global securities, except in the event that use of the book-entry system for the global securities is discontinued.

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To facilitate subsequent transfers, all securities deposited by direct participants with DTC are registered in the name of Cede & Co. or such other name as may be requested by an authorized representative of DTC. The deposit of securities with DTC and their registration in the name of Cede & Co. or such other nominee do not effect any change in beneficial ownership. DTC has no knowledge of the actual beneficial owners of the securities. DTC’s records reflect only the identity of the direct participants to whose accounts such securities are credited, which may or may not be the beneficial owners. The direct and indirect participants remain responsible for keeping account of their holdings on behalf of their customers.

Conveyance of notices and other communications by DTC to direct participants, by direct participants to indirect participants and by direct participants and indirect participants to beneficial owners will be governed by arrangements among them, subject to any statutory or regulatory requirements as may be in effect from time to time.

If a particular series of securities is redeemable at our option or at the option of the holder, redemption notices will be sent to DTC. If less than all of the securities of a series are being redeemed, DTC’s practice is to determine by lot the amount of the interest of each direct participant in such series to be redeemed. Redemption proceeds and distributions on global securities will be made to Cede & Co. or such other nominee as may be requested by an authorized representative of DTC. Upon DTC’s receipt of funds and corresponding detail information from us, any trustee or any paying agent, DTC’s practice is to credit direct participants’ accounts in accordance with the holdings information shown on DTC’s records on the payment date. Payments by participants to beneficial owners of securities will be governed by standing instructions and customary practices, as is the case with securities held for the accounts of customers in bearer form or registered in “street name.” Payments will be the responsibility of such participant and not of DTC nor its nominee, any trustee, any paying agent or us, subject to any statutory or regulatory requirements. Payment of redemption proceeds and distributions to Cede & Co. or such other nominee as may be requested by an authorized representative of DTC is the responsibility of us, the applicable trustee or the applicable paying agent, disbursement of such payments to direct participants will be the responsibility of DTC, and disbursement of such payments to the beneficial owners will be the responsibility of direct and indirect participants.

Neither DTC nor Cede & Co. or any other DTC nominee will consent or vote with respect to global securities unless authorized by a direct participant in accordance with DTC’s procedures. Under its usual procedures, DTC mails an omnibus proxy to us as soon as possible after the record date. The omnibus proxy assigns Cede & Co.’s consenting or voting rights to those direct participants to whose accounts the securities are credited on the record date as identified in a listing attached to the omnibus proxy.

Global securities will be exchangeable for corresponding certificated securities registered in the name of persons other than DTC or its nominee if (1) DTC (a) notifies us that it is unwilling or unable to continue as depository for any of the global securities or (b) at any time ceases to be a clearing agency registered under the Exchange Act, (2) an event of default occurs and is continuing with respect to the applicable series of securities or (3) we execute and deliver to the applicable trustee an order that the global securities will be so exchangeable.

The information in this section concerning DTC and DTC’s book-entry system has been obtained from DTC, and we and any underwriters, dealers or agents are not responsible for the accuracy of the information or for the performance by DTC of its obligations under the rules and procedures governing its operations or otherwise.

Any underwriters, dealers or agents of any securities may be direct participants of DTC.

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PLAN OF DISTRIBUTION

We may sell the securities offered under this prospectus through underwriters or dealers, through agents or directly to one or more purchasers. The terms under which the securities are offered and the method of distribution will be set forth in the applicable prospectus supplement.

Underwriters, dealers and agents that participate in the distribution of the securities offered under this prospectus may be underwriters as defined in the Securities Act of 1933, as amended, the “Securities Act,” and any discounts or commissions received by them from us and any profit on the resale of the offered securities by them may be treated as underwriting discounts and commissions under the Securities Act. Any underwriters or agents will be identified and their compensation, including any underwriting discount or commission, will be described in the applicable prospectus supplement. The applicable prospectus supplement will also describe other terms of the offering, including the initial public offering price and any discounts or concessions allowed or reallowed to dealers.

The distribution of the securities described in this prospectus may be effected from time to time in one or more transactions at a fixed price or prices, which may be changed, at market prices prevailing at the time of sale, at prices related to the prevailing market prices or at negotiated prices.

We may determine the price or other terms of the securities offered under this prospectus by use of an electronic auction. We will describe in the applicable prospectus supplement how any auction will be conducted to determine the price or any other terms of the securities, how potential investors may participate in the auction and, where applicable, the nature of the underwriters’ obligations with respect to the auction.

Each series of securities will be a new issue of securities and will have no established trading market. Any underwriters to whom securities are sold for public offering and sale may make a market in such securities, but such underwriters will not be obligated to do so and may discontinue any market making at any time without notice. The securities may or may not be listed on a national securities exchange.

Under agreements into which we may enter in connection with the sale of the securities, underwriters, dealers and agents who participate in the distribution of the securities may be entitled to indemnification by us against specified liabilities, including liabilities under the Securities Act.

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LEGAL OPINIONS

Unless otherwise indicated in the applicable prospectus supplement, legal opinions relating to the validity of the securities being offered by this prospectus will be rendered by our counsel, James L. Altman, Minneapolis, Minnesota. Unless otherwise indicated in the prospectus supplement relating to a particular series of securities, certain legal matters will be passed upon for the underwriters, dealers or agents named in a prospectus supplement by Hunton Andrews Kurth LLP, New York, New York. James L. Altman is the Vice President and Deputy General Counsel of Xcel Energy Services Inc., and is the beneficial owner of less than 1% of the common stock of our parent company, Xcel Energy Inc.

EXPERTS

The consolidated financial statements, and the related financial statement schedule, incorporated in this prospectus by reference from Northern States Power Company’s, a Wisconsin corporation, Annual Report on Form 10-K have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their report, which is incorporated herein by reference. Such consolidated financial statements and financial statement schedule have been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

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PROSPECTUS

PUBLIC SERVICE COMPANY OF COLORADO

1800 Larimer Street, Suite 1100

Denver, Colorado 80202

(303) 571-7511

FIRST MORTGAGE BONDS

SENIOR DEBT SECURITIES

We may offer and sell from time to time, in one or more offerings, together or separately, any combination of the securities listed above and described in this prospectus. We may offer and sell these securities to or through one or more underwriters, dealers and/or agents, or directly to purchasers, on a continuous or delayed basis.

This prospectus describes some of the general terms that may apply to the securities and the general manner in which they may be offered. The specific terms of any securities to be offered, and the specific manner in which they may be offered, will be described in a supplement to this prospectus. This prospectus may not be used to sell securities unless accompanied by a prospectus supplement.

You should carefully consider the risk factors set forth in the applicable prospectus supplement and certain of our filings with the Securities and Exchange Commission before making any decision to invest in any of the securities described in this prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is April 18, 2018.

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ABOUT THIS PROSPECTUS

This document is called a “prospectus” and it provides you with a general description of the securities we may offer. Each time we sell securities under this prospectus, we will provide a prospectus supplement containing specific information about the terms of the securities being offered. That prospectus supplement may include a discussion of any risk factors or other special considerations that apply to those securities. The prospectus supplement may also add, update or change the information in this prospectus. If there is any inconsistency between the information in this prospectus and in the prospectus supplement, you should rely on the information in the prospectus supplement. You should read this prospectus and the applicable prospectus supplement together with the additional information described under the caption “Where You Can Find More Information.” We may also prepare free writing prospectuses that describe particular securities. Any free writing prospectus should also be read in connection with this prospectus and with the prospectus supplement referred to therein. For purposes of this prospectus, any reference to an applicable prospectus supplement may also refer to a free writing prospectus, unless the context otherwise requires.

This prospectus is part of a registration statement that we filed with the Securities and Exchange Commission, or the “SEC,” using a shelf registration process. As permitted by SEC rules, this prospectus does not contain all of the information included in the registration statement and the accompanying exhibits and schedules we filed with the SEC. You should read the registration statement and the related exhibits and schedules for more information about us and our securities. The registration statement and the related exhibits and schedules can be read at the SEC’s website or at the SEC’s offices. The SEC’s website and street addresses are provided under the caption “Where You Can Find More Information.”

The distribution of this prospectus and the applicable prospectus supplement and the offering of the securities in certain jurisdictions may be restricted by law. Persons into whose possession this prospectus and the applicable prospectus supplement come should inform themselves about and observe any such restrictions. This prospectus and the applicable prospectus supplement do not constitute, and may not be used in connection with, an offer or solicitation by anyone in any jurisdiction in which such offer or solicitation is not authorized or in which the person making such offering or solicitation is not qualified to do so or to any person to whom it is unlawful to make such offer or solicitation.

This prospectus, the applicable prospectus supplement and any free writing prospectus that we prepare or authorize contain and incorporate by reference information that you should consider when making your investment decision. No one is authorized to provide you with information different from that which is contained, or deemed to be contained, in this prospectus and applicable prospectus supplement. We are not making an offer of these securities in any jurisdiction where the offer is not permitted. You should not assume that the information in this prospectus or the documents incorporated by reference is accurate as of any date other than the date on the front of those documents.

Unless otherwise specified or unless the context requires otherwise, all references in this prospectus “PSCo,” “we,” “us,” “our,” and “the Company” or similar terms refer to Public Service Company of Colorado.

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WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and current reports and other information with the SEC. Our SEC filings are available to the public on the SEC’s website at http://www.sec.gov. You may also read and copy any document we file with the SEC at the SEC’s Public Reference Room located at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information on the Public Reference Room.

The SEC allows us to “incorporate by reference” the information we file with it, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is an important part of this prospectus, and information that we file later with the SEC will automatically update and supersede this information. We incorporate by reference our Annual Report on Form 10-K for the year ended December 31, 2017, including information specifically incorporated by reference into our Form 10-K from Xcel Energy Inc.’s definitive Proxy Statement for its 2018 Annual Meeting of Shareholders, and any future filings made with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, or the Exchange Act, from the date of the prospectus until we sell all of the securities (other than, in each case, documents or information deemed to have been furnished and not filed in accordance with SEC rules).

We will provide, without charge, to each person, including any beneficial owner of our securities to whom this prospectus is delivered, upon written or oral request, a copy of any or all documents referred to above that have been incorporated by reference into this prospectus, excluding exhibits to those documents unless they are specifically incorporated by reference into those documents. You may request these documents from:

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OUR COMPANY

We were incorporated in 1924 under the laws of the State of Colorado. We are an operating utility engaged primarily in the generation, purchase, transmission, distribution and sale of electricity in Colorado. We also purchase, transport, distribute and sell natural gas to retail customers and transport customer-owned natural gas. At December 31, 2017, we provided electric utility service to approximately 1.5 million customers and natural gas utility service to approximately 1.4 million customers.

We own the following direct subsidiaries: 1480 Welton, Inc. and United Water Company, both of which own certain real estate interests; and Green and Clear Lakes Company, which owns water rights and certain real estate interests. We also hold controlling interests in several other relatively small ditch and water companies.

Our principal executive offices are located at 1800 Larimer Street, Suite 1100, Denver, Colorado 80202 and our telephone number is (303) 571-7511.

DESCRIPTION OF THE FIRST MORTGAGE BONDS

The description below contains summaries of selected provisions of the mortgage indenture, including supplemental indentures, under which the first mortgage bonds will be issued. These summaries are not complete. The mortgage indenture and the form of supplemental indenture, including the form of first mortgage bond, applicable to the first mortgage bonds have been filed or incorporated by reference as exhibits to the registration statement of which this prospectus is a part. You should read them for provisions that may be important to you. In the summaries below, we have included references to section numbers of the mortgage indenture so that you can easily locate these provisions. Capitalized terms used in the following summary have the meaning specified in the mortgage indenture unless otherwise defined below.

We are not required to issue future issues of indebtedness under the mortgage indenture described below. We are free to use other indentures or documentation, containing provisions different from those described in this prospectus, in connection with future issues of other indebtedness not issued under this prospectus.

The first mortgage bonds will be represented either by global securities registered in the name of The Depository Trust Company, or DTC, as depository, or the Depository, or its nominee, or by securities in certificated form issued to the registered owners, as set forth in the applicable prospectus supplement. See the information under the caption “Book-Entry System” in this prospectus.

General

We may issue the first mortgage bonds from time to time in one or more series under an Indenture, dated as of October 1, 1993, as previously supplemented and to be supplemented by one or more new supplemental indentures relating to the first mortgage bonds being offered by this prospectus, all from us to U.S. Bank National Association (formerly First Trust of New York, National Association) as successor trustee, which we collectively refer to as the Mortgage Indenture. We refer to the first mortgage bonds being offered by this prospectus and all other debt securities issued under the Mortgage Indenture as the first mortgage bonds, mortgage securities or mortgage bonds. References to business day(s) in this description of the first mortgage bonds means any day, other than a Saturday or Sunday, which is not a day on which banking institutions or trust companies in New York, New York (or any other city in which an office or agency is maintained for the purpose of payment of the first mortgage bonds) are generally authorized or required by law, regulation or executive order to remain closed.

The Mortgage Indenture does not limit the amount of mortgage securities that we may issue under it. However, we may issue mortgage securities under the Mortgage Indenture only on the basis of property additions, retired mortgage securities, cash or Class A Bonds (as discussed below). See “—Issuance of Additional Mortgage Securities” for more information about the limitations on the issuance of mortgage securities. At December 31, 2017, we had approximately $4.5 billion of our first mortgage bonds outstanding.

Prior to October 2005, we issued mortgage securities on the basis of Class A Bonds issued under our Indenture dated as of December 1, 1939 and supplemental indentures thereto, which we collectively refer to as the 1939 Indenture. Effective October 14, 2005, we discharged the 1939 Indenture in accordance with its terms. As a result, there are no Class A Mortgages (as discussed below) currently in effect and there are no Class A Bonds currently outstanding and the Mortgage Indenture has become the first lien on our electric properties, subject to certain permitted liens, and as described in more detail below.

The holders of outstanding first mortgage bonds do not, and, unless the prospectus supplement that describes a particular series of first mortgage bonds provides otherwise with respect to that series, the holders of any first mortgage bonds offered by this prospectus will not, have the right to require us to repurchase the first mortgage bonds if we become involved in a highly leveraged or change of control transaction. The Mortgage Indenture does not have any provision that is designed specifically in response to highly leveraged or change of

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control transactions. However, holders of first mortgage bonds would have the security afforded as described below under the caption “—Security.” In addition, any change in control transaction and any incurrence of substantial additional indebtedness, as first mortgage bonds or otherwise, by us in a transaction of that nature would require approval of state utility regulatory authorities and, possibly, of federal utility regulatory authorities. Management believes that these approvals would be unlikely in any transaction that would result in us, or our successor, having a highly leveraged capital structure.

When we offer to sell a particular series of first mortgage bonds, we will describe the specific terms of that series in a prospectus supplement relating to that series, including the following terms:

(Section 301 of the Mortgage Indenture)

Unless the prospectus supplement that describes a particular series of first mortgage bonds provides otherwise, we may from time to time, without the consent of the holders of that series of first mortgage bonds, reopen that series of first mortgage bonds and issue additional first mortgage bonds with the same terms (including maturity and interest payment terms) as that series of first mortgage bonds.

Payment of First Mortgage Bonds; Transfers; Exchanges

Unless the prospectus supplement that describes a particular series of first mortgage bonds provides otherwise with respect to that series, we will pay interest, if any, on each first mortgage bond payable on each interest payment date to the person in whose name the first mortgage bond is registered as of the close of business on the regular record date relating to that interest payment date. We will pay interest payable at maturity (whether at stated maturity, upon redemption or otherwise) to the person to whom principal is paid at maturity. If we fail to pay interest on any first mortgage bond when due, we will pay the defaulted interest to the holder of the first mortgage bond as of the close of business on a date selected by the Mortgage Indenture trustee which is not more than 30 days and not less than 10 days prior to the date we propose for payment or in any other lawful manner not inconsistent with the requirements of any securities exchange on which the first mortgage bond may be listed, if the Mortgage Indenture trustee deems the manner of payment practicable. (See Section 307 of the Mortgage Indenture)

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Unless the prospectus supplement that describes a particular series of first mortgage bonds provides otherwise with respect to that series, we will pay the principal of and premium, if any, and interest at maturity upon presentation of the first mortgage bonds at the corporate trust office of U.S. Bank National Association (formerly First Trust of New York, National Association) in New York, New York, as our paying agent. We may change the place of payment on the bonds. We may appoint one or more additional paying agents (including us) and may remove any paying agent, all at our discretion. (See Section 602 of the Mortgage Indenture and Article One of the Supplemental Indenture(s) relating to the first mortgage bonds)

Unless the prospectus supplement that describes a particular series of first mortgage bonds provides otherwise with respect to that series, you may register the transfer of first mortgage bonds, and exchange your first mortgage bonds for other first mortgage bonds of the same series and tranche, of authorized denominations and of like tenor and aggregate principal amount, at the corporate trust office of U.S. Bank National Association (formerly First Trust of New York, National Association), in New York, New York, as security registrar. We may change the place for registration of transfer and exchange of first mortgage bonds, and we may designate one or more additional places for the registration of transfer and exchange of first mortgage bonds, all at our discretion. (See Sections 305 and 602 of the Mortgage Indenture)

Unless the prospectus supplement that describes a particular series of first mortgage bonds provides otherwise with respect to that series, no service charge will be made for any transfer or exchange of the first mortgage bonds, but we may require payment of a sum sufficient to cover any tax or other governmental charge imposed in connection with any registration of transfer or exchange of the first mortgage bonds. We are not required to execute or to provide for the registration of transfer or exchange of (1) any first mortgage bonds during a period of 15 days prior to giving any notice of redemption or (2) any first mortgage bonds selected for redemption in whole or in part, except the unredeemed portion of any first mortgage bonds being redeemed in part. (See Section 305 of the Mortgage Indenture)

Redemption

The prospectus supplement that describes a particular series of first mortgage bonds will set forth any terms for the optional or mandatory redemption of that particular series. Unless the prospectus supplement that describes a particular series of first mortgage bonds provides that such series of first mortgage bonds are redeemable at the option of a holder, the first mortgage bonds will be redeemable only at our option. To exercise our option to redeem any first mortgage bonds that are redeemable at our option, we will mail you a notice of redemption at least 30 days but not more than 60 days prior to the date fixed for redemption. If we elect to redeem fewer than all the first mortgage bonds of a series or any tranche of first mortgage bonds, the security registrar will select the particular first mortgage bonds to be redeemed by the method provided for any particular series, or if there is no such provision, by a method of random selection that the security registrar deems fair and appropriate. (See Sections 503 and 504 of the Mortgage Indenture)

Any notice of redemption at our option may state that the redemption will be conditional upon receipt by the paying agent or agents, on or prior to the date fixed for the redemption, of money sufficient to pay the principal, premium, if any, and interest, if any, on the first mortgage bonds and that if the money has not been so received, the notice will be of no force and effect and we will not be required to redeem the first mortgage bonds. (See Section 504 of the Mortgage Indenture)

While the original Mortgage Indenture contains provisions for the maintenance of the mortgaged property, it does not contain any provisions for a maintenance or sinking fund and, except as the prospectus supplement may provide, there will be no provisions for any maintenance or sinking funds for the first mortgage bonds.

Security

General . Except as discussed under this caption and under the caption “—Issuance of Additional Mortgage Securities” below, all mortgage securities now or hereafter issued under the Mortgage Indenture will be secured,

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equally and ratably, primarily by the lien of the Mortgage Indenture on substantially all of our properties used or to be used in or in connection with the business of generating, purchasing, transmitting, distributing and/or selling electric energy, which lien constitutes, subject to specified exceptions, a first mortgage lien on such properties.

As discussed below under the caption “—Issuance of Additional Mortgage Securities—Class A Bonds,” if we acquire property subject to an existing mortgage and we assume all the obligations of the mortgagor under that mortgage, we could deliver to the Mortgage Indenture trustee bonds issued under that mortgage. We refer to all such pre-existing mortgages collectively as Class A Mortgages. If we were to deliver to the Mortgage Indenture trustee bonds issued under a Class A Mortgage, the mortgage securities would be secured by those bonds and, indirectly, by the lien of that Class A Mortgage on the properties subject to that Class A Mortgage in addition to the lien of the Mortgage Indenture on those properties and the other properties of the Company as discussed above. The lien of the Mortgage Indenture on the properties subject to that Class A Mortgage would be junior to the liens of the Class A Mortgage on those properties. We refer to all bonds that may be issued under the Class A Mortgages collectively as Class A Bonds.

So long as no Class A Mortgages are in effect, the Mortgage Indenture will constitute a first mortgage lien on all of our property subject to such lien, subject to specified permitted liens (as discussed below under the caption “—Lien of the Mortgage Indenture”). As discussed below under the caption “—Issuance of Additional Mortgage Securities—Class A Bonds,” at the date of this prospectus, there are no Class A Mortgages in effect.

Lien of the Mortgage Indenture. The Mortgage Indenture constitutes a first mortgage lien on the property specifically or generally described or referred to in the Mortgage Indenture as subject to the lien of the Mortgage Indenture, except any property that has been disposed of or released from the lien of the Mortgage Indenture in accordance with the terms of the Mortgage Indenture, subject to no liens prior to the lien of the Mortgage Indenture other than the liens of any other Class A Mortgages and permitted liens.

Subject to recordation of appropriate supplements in the proper offices, the Mortgage Indenture effectively subjects to the lien of the Mortgage Indenture property used or to be used in the electric utility business (other than excepted property) that we acquired after the date of the execution and delivery of the Mortgage Indenture to the extent, and subject to the qualifications, described below. In addition, the mortgage securities will have the benefit of the prior lien of any Class A Mortgage on any property subject to such additional Class A Mortgage, to the extent of the aggregate principal amount of Class A Bonds issued under the respective Class A Mortgages and held by the Mortgage Indenture trustee for the benefit of holders of mortgage securities.

The properties subject to the lien of the Mortgage Indenture, whether currently owned or subsequently acquired, are our properties used or to be used in or in connection with the electric utility business (whether or not this is the sole use of the properties). Properties relating exclusively to our gas and steam businesses are not subject to the lien of the Mortgage Indenture.

The lien of the Mortgage Indenture is subject to permitted liens, which include:

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(See Granting Clauses and Section 101 of the Mortgage Indenture)

There are excepted from the lien of the Mortgage Indenture, among other things:

(See “Excepted Property” in Granting Clauses of the Mortgage Indenture)

Without the consent of the holders, we and the Mortgage Indenture trustee may enter into supplemental indentures in order to subject to the lien of the Mortgage Indenture additional property, whether or not used or to be used in or in connection with the electric utility business (including property which would otherwise be excepted from the lien). (See Section 1401 of the Mortgage Indenture) Any such additional property would then constitute property additions (so long as it would otherwise qualify as “property additions” as described below) and be available as a basis for the issuance of mortgage securities. See “—Issuance of Additional Mortgage Securities.”

As discussed above, the Mortgage Indenture subjects after-acquired property used or to be used in the electric utility business to its lien. These provisions are limited in the case of consolidation or merger (whether or not we are the surviving corporation) or transfer of the mortgaged property as, or substantially as, an entirety. In the event of consolidation or merger or the transfer of the mortgaged property as or substantially as an entirety, the Mortgage Indenture will not be required to be a lien upon any of the properties then owned or subsequently

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acquired by the successor corporation except properties acquired from us in or as a result of the transaction and improvements, extensions and additions to the properties and renewals, replacements and substitutions of or for any part or parts of the properties. (See Article 13 of the Mortgage Indenture and “—Consolidation, Merger, etc.” below) In addition, after-acquired property may be subject to liens existing or placed on the after-acquired property at the time of acquisition of the property, including, but not limited to, purchase money liens and the lien of any Class A Mortgage.

The Mortgage Indenture trustee has a lien, prior to the lien on behalf of the holders of mortgage securities, upon the mortgaged property for the payment of its reasonable compensation and expenses and for indemnity against specified liabilities. (See Section 1107 of the Mortgage Indenture)

Issuance of Additional Mortgage Securities

General . Except as described below, the aggregate principal amount of mortgage securities that we can issue under the Mortgage Indenture is unlimited. (See Section 301 of the Mortgage Indenture) We can issue mortgage securities of any series from time to time on the basis, and in an aggregate principal amount not exceeding the sum, of:

(See Article Four of the Mortgage Indenture)

As of December 31, 2017, the approximate amount of property additions and the amount of retired bonds available for use as the basis for the issuance of mortgage securities were $6.8 billion and $263 million, respectively.

Net Earnings Test. In general, we cannot issue any mortgage securities unless at that time our adjusted net earnings for 12 consecutive months within the preceding 18 months is at least twice the annual interest requirements on the sum of:

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For purposes of calculating our interest requirements, any variable rate debt will be computed based on the rates in effect at the time we make the interest requirements calculation.

Adjusted net earnings are calculated before, among other things, provisions for income taxes; depreciation or amortization of property; interest and amortization of debt discount and expense; any non-recurring charge to income or retained earnings; and any refund of revenues that we previously collected or accrued subject to possible refund. In addition, profits or losses from the sale or other disposition of property, or non-recurring items of revenue, income or expense, are not included for purposes of calculating adjusted net earnings. (See Sections 103 and 401 of the Mortgage Indenture)

We do not have to satisfy the net earnings requirement if the additional mortgage securities to be issued will not have a stated interest rate prior to maturity. In addition, we are not required to satisfy the net earnings requirement prior to the issuance of mortgage securities:

For mortgage securities of a series subject to a periodic offering (such as a medium-term note program), the Mortgage Indenture trustee will be entitled to receive a certificate evidencing compliance with the net earnings requirements only once, at or prior to the time of the first authentication and delivery of the mortgage securities of the series. (See Article Four of the Mortgage Indenture)

At December 31, 2017, our adjusted net earnings would be 4.74 times the annual interest requirements on our mortgage securities.

Class  A Bonds. To the extent that we issue the first mortgage bonds on the basis of Class A Bonds, the Mortgage Indenture trustee will own and hold these Class A Bonds, subject to the provisions of the Mortgage Indenture, for the benefit of the holders of all mortgage securities outstanding from time to time, and we will have no interest in the Class A Bonds. Class A Bonds issued as the basis of authentication and delivery of a series of mortgage securities:

Class A Bonds issued as the basis for the authentication and delivery of mortgage securities are not required to bear interest. To the extent that any such Class A Bonds do not bear interest, holders of mortgage securities will not have the benefit of the lien of the Class A Mortgage in respect of an amount equal to accrued interest, if any, on the first mortgage bonds; however, those holders will have the benefit of the lien of the Mortgage Indenture in respect of that amount.

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The Mortgage Indenture trustee will apply any of our payments of principal, premium or interest on the Class A Bonds held by the Mortgage Indenture trustee to the payment of any principal, premium or interest, as the case may be, in respect of the mortgage securities that is then due. Our obligation under the Mortgage Indenture to make the payment in respect of the mortgage securities will at that time be deemed satisfied and discharged. If, at the time of any payment of principal of Class A Bonds, no principal is then due in respect of the mortgage securities, the payment in respect of the Class A Bonds will be deemed to constitute funded cash and will be held by the Mortgage Indenture trustee as part of the mortgaged property, to be withdrawn, used or applied as provided in the Mortgage Indenture. Any payment by us of principal, premium or interest on the mortgage securities authenticated and delivered on the basis of the issuance and delivery to the Mortgage Indenture trustee of Class A Bonds (other than by application of the proceeds of a payment in respect of the Class A Bonds) will be deemed to satisfy and discharge our obligation to make a payment of principal, premium or interest, in respect of the Class A Bonds that is then due. (See Section 702 of the Mortgage Indenture)

The Mortgage Indenture trustee may not sell, assign or otherwise transfer any Class A Bonds except to a successor trustee under the Mortgage Indenture. (See Section 704 of the Mortgage Indenture) At the time any mortgage securities of any series or tranche that have been authenticated and delivered upon the basis of the issuance and delivery to the Mortgage Indenture trustee of Class A Bonds cease to be outstanding (other than as a result of the application of the proceeds of the payment or redemption of the Class A Bonds), the Mortgage Indenture trustee will surrender to us an equal principal amount of those Class A Bonds. (See Section 703 of the Mortgage Indenture)

Under the terms of the Mortgage Indenture, if a corporation that was a mortgagor under a mortgage has merged into or consolidated with us, or has conveyed or otherwise transferred property to us subject to the lien of such a mortgage and we have assumed all the obligations of the mortgagor under such existing mortgage, and in either case such existing mortgage constitutes a lien on properties of such other corporation or on the transferred properties, as the case may be, prior to the lien of the Mortgage Indenture, we may designate the existing mortgage as a Class A Mortgage. Bonds subsequently issued under an additional mortgage would be Class A Bonds and could provide the basis for the authentication and delivery of mortgage securities. (See Section 706 of the Mortgage Indenture) When no Class A Bonds are outstanding under a Class A Mortgage except for Class A Bonds held by the Mortgage Indenture trustee, then, at our request and subject to satisfaction of specified conditions, the Mortgage Indenture trustee will surrender the Class A Bonds for cancellation and the related Class A Mortgage will be satisfied and discharged, the lien of the Class A Mortgage on our property will cease to exist and the priority of the lien of the Mortgage Indenture will be increased accordingly. (See Section 707 of the Mortgage Indenture)

The Mortgage Indenture contains no restrictions on the issuance of Class A Bonds in addition to Class A Bonds issued to the Mortgage Indenture trustee as the basis for the authentication and delivery of the mortgage securities.

DESCRIPTION OF THE SENIOR DEBT SECURITIES

The description below contains summaries of selected provisions of the indenture, including supplemental indentures, under which the unsecured senior debt securities, which we refer to as debt securities or senior debt securities, will be issued. These summaries are not complete. The indenture and the form of supplemental indenture, including the form of senior debt security, applicable to the senior debt securities have been filed or incorporated by reference as exhibits to the registration statement of which this prospectus is a part. You should read them for provisions that may be important to you. In the summaries below, we have included references to section numbers of the indenture so that you can easily locate these provisions. Capitalized terms used in the following summary have the meaning specified in the indenture unless otherwise defined below.

We are not required to issue future issues of indebtedness under the indenture described below. We are free to use other indentures or documentation, containing provisions different from those described in this prospectus, in connection with future issues of other indebtedness not issued under this prospectus.

The senior debt securities will be represented either by global securities registered in the name of DTC, as the Depository, or its nominee, or by securities in certificated form issued to the registered owners, as set forth in the applicable prospectus supplement. See the information under the caption “Book-Entry System” in this prospectus.

General

We may issue senior debt securities from time to time in one or more series under an Indenture, dated as of July 1, 1999, as previously supplemented and to be supplemented by one or more supplemental indentures relating to the senior debt securities being offered by this prospectus, all from us to The Bank of New York Mellon Trust Company, N.A., as trustee, which we collectively refer to as the Indenture. The Indenture does not contain any debt covenants or provisions that would afford holders of the senior debt securities protection in the event of a highly leveraged transaction.

The senior debt securities will be our unsecured obligations. The Indenture does not limit the aggregate principal amount of senior debt securities that we may issue under the Indenture and does not limit the incurrence or issuance of other secured or unsecured debt by us. (See Section 301 of the Indenture) As of December 31, 2017, there were no senior debt securities outstanding under the Indenture. As of December 31, 2017, there was approximately $4.5 billion aggregate principal amount of our first mortgage bonds outstanding under our Mortgage Indenture. The Mortgage Indenture constitutes, subject to specified exceptions, a first mortgage lien on substantially all of our properties used or to be used in or in connection with the business of generating, purchasing, transmitting, distributing and/or selling electric energy (See “Description of the First Mortgage Bonds”).

The senior debt securities will rank as equal in right of payment to our other unsecured indebtedness, except for any indebtedness that, by its terms, is subordinate to the senior debt securities.

When we offer to sell a particular series of senior debt securities, we will describe the specific terms of that series in a prospectus supplement relating to that series, including the following terms:

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(See Section 301 of the Indenture)

Unless the prospectus supplement that describes a particular series of senior debt securities provides otherwise, we may from time to time, without the consent of the holders of that series of senior debt securities, reopen that series of senior debt securities and issue additional senior debt securities with the same terms (including maturity and interest payment terms) as that series of senior debt securities.

Periodic Offering

We may offer senior debt securities of any series in a periodic offering in which any or all of the specific terms of each security of the series may vary from other securities of that series, including with respect to rate or rates of interest on the securities, if any, the stated maturity of each security, the redemption provisions, if any, and such other terms as may be permitted by the Indenture and determined by us from time to time as provided in the Indenture and described in the applicable prospectus supplement.

Discount Security

A senior debt security may provide that an amount less than the principal amount of the senior debt security would be due and payable if it were to be accelerated because of an event of default. Senior debt securities containing such a provision would be offered and sold at a substantial discount below their principal amount. Special federal income tax, accounting and other considerations relating to those securities will be described in the applicable prospectus supplement.

Payment of Senior Debt Securities; Transfers; Exchanges

Unless the prospectus supplement that describes a particular series of senior debt securities says otherwise with respect to that series, we will pay interest, if any, on each senior debt security payable on each interest payment date to the person in whose name the senior debt security is registered as of the close of business on the regular record date relating to that interest payment date. We will pay interest payable at maturity to the person to whom principal is paid at maturity. If there has been a default in the payment of interest on any senior debt security, the defaulted interest may be paid to the holder of the senior debt security as of the close of business on a date selected by the senior debt security trustee. The date selected must not be more than 15 days and not less

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than 10 days prior to the date we propose for payment of the defaulted interest. Defaulted interest may also be paid in any other lawful manner permitted by requirements of any securities exchange on which the senior debt security may be listed, if the Indenture trustee deems the manner of payment practicable. (See Section 307 of the Indenture)

Unless the prospectus supplement that describes a particular series of senior debt securities says otherwise with respect to that series, the principal of and premium, if any, and interest at maturity will be payable upon presentation of the senior debt securities at the corporate trust office of The Bank of New York Mellon Trust Company, N.A., as our Paying Agent. We may change the place of payment. We may appoint one or more additional paying agents and may remove any paying agent, all at our discretion. (See Section 1002 of the Indenture)

Unless the prospectus supplement that describes a particular series of senior debt securities says otherwise with respect to that series, the transfer of senior debt securities may be registered, and senior debt securities may be exchanged for other senior debt securities of the same series and tranche, of authorized denominations and of like tenor and aggregate principal amount, at the corporate trust office of The Bank of New York Mellon Trust Company, N.A., as security registrar. We may change the place for registration of transfer and exchange of senior debt securities, and we may designate one or more additional places for the registration of transfer and exchange of senior debt securities, all at our discretion. (See Sections 305 and 1002 of the Indenture)

Unless the prospectus supplement that describes a particular series of senior debt securities says otherwise with respect to that series, no fee for service will be charged for any transfer or exchange of the senior debt securities, but we may require payment of a sum sufficient to cover any tax or other governmental charge imposed in connection with any registration of transfer or exchange of the senior debt securities. We are not required to execute or to provide for the registration of transfer or exchange of (1) any senior debt security during a period of 15 days prior to giving any notice of redemption or (2) any senior debt security selected for redemption in whole or in part, except the unredeemed portion of any senior debt security being redeemed in part. (See Section 305 of the Indenture)

Redemption

The prospectus supplement that describes a series of senior debt securities will set forth any terms for the optional or mandatory redemption of that particular series. Unless the prospectus supplement says that senior debt securities are redeemable at the option of a holder, senior debt securities that are redeemable will be redeemable only at our option upon notice by mail at least 30 days prior to the date fixed for redemption. If fewer than all the senior debt securities of a series are to be redeemed, the particular senior debt securities to be redeemed will be selected by the trustee by the method provided for that series or, if no method is provided, substantially pro rata, by lot or by any other method as the trustee considers fair and appropriate and which complies with the requirement of the principal national securities exchange, if any, on which the senior debt securities are listed. If senior debt securities of a series or tranche have different terms and different maturities, we may select the particular senior debt securities to be redeemed. (See Sections 1103 and 1104 of the Indenture)

If redemption is at our option, the notice of redemption may state that the redemption will be conditional upon receipt by the paying agent or agents, on or prior to the date fixed for the redemption, of money sufficient to redeem all of the senior debt securities called for redemption, including accrued interest, if any. If no money has been received, the notice will not be effective and we will not be required to redeem the senior debt securities. (See Section 1104 of the Indenture)

Consolidation, Merger or Sale

The Indenture provides that we will not consolidate with or merge with or into any other corporation, whether or not we are the surviving corporation, or sell, assign, transfer or lease all or substantially all of our

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properties and assets as an entirety or substantially as an entirety to any person or group of affiliated persons, in one transaction or a series of related transactions, unless:

(See Article Eight of the Indenture)

Events of Default

The following are events of default under the Indenture with respect to senior debt securities of any series issued under the Indenture:

(See Section 501 of the Indenture)

Remedies

Acceleration of Maturity . If an event of default with respect to senior debt securities of any series, other than due to events of bankruptcy, insolvency or reorganization, occurs and is continuing, the Indenture trustee or

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the holders of at least 25% in aggregate principal amount of the outstanding senior debt securities of that series, by notice in writing to us, and to the Indenture trustee if given by the holders of at least 25% in aggregate principal amount of the senior debt securities of that series, may declare the unpaid principal of and accrued interest to the date of acceleration, or, if the senior debt securities are original issue discount securities, the portion of that principal as may be specified in the terms of the Indenture, on all the outstanding senior debt securities of that series to be due and payable immediately and, upon any such declaration, the senior debt securities of that series, or specified principal amount, will become immediately due and payable. (See Section 502 of the Indenture)

If an event of default occurs due to bankruptcy, insolvency or reorganization, all unpaid principal of and accrued interest on the outstanding senior debt securities of all series will become immediately due and payable without any declaration or other act on the part of the Indenture trustee or any holder of any senior debt security. (See Section 502 of the Indenture)

The holders of a majority of the principal amount of the outstanding senior debt securities of that series, upon the conditions provided in the Indenture, may rescind an acceleration and its consequences. (See Section 502 of the Indenture)

Right to Direct Proceedings. The holders of a majority in principal amount of the outstanding senior debt securities of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the Indenture trustee, or exercising any trust or power conferred on the Indenture trustee, with respect to the senior debt securities of that series; provided that (1) the direction is not in conflict with any law or the Indenture; (2) the Indenture trustee may take any other action deemed proper by the Indenture trustee that is not inconsistent with the direction; and (3) subject to its duties under the Trust Indenture Act, the Indenture trustee need not take any action that might involve the Indenture trustee in personal liability or might be unduly prejudicial to the holders not joining in the action. (See Section 512 of the Indenture)

Limitation on Rights to Institute Proceedings. No holder of the senior debt securities of any series will have any right to institute any proceeding with respect to the Indenture, or for the appointment of a receiver or a trustee, or for any other remedy under the Indenture, unless:

(See Section 507 of the Indenture)

No Impairment of Right to Receive Payment. Notwithstanding any other provision of the Indenture, the holder of any senior debt security will have the absolute and unconditional right to receive payment of the principal of (and premium, if any) and interest on that senior debt security when due, and to institute suit for enforcement of that payment. This right may not be impaired without the consent of the holder. (See Section 508 of the Indenture)

Notice of Default. The Indenture provides that the Indenture trustee must, within 30 days after the occurrence of any default or event of default with respect to senior debt securities of any series issued under the Indenture, give the holders of senior debt securities of that series notice of all uncured defaults or events of

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default known to it (the term “default” includes any event that after notice or passage of time or both would be an event of default); provided, however, that, except in the case of an event of default or a default in payment on any senior debt securities of any series, the Indenture trustee will be protected in withholding the notice if and so long as the board of directors, the executive committee or directors or responsible officers of the Indenture trustee in good faith determine that the withholding of the notice is in the interest of the holders of senior debt securities of the affected series. (See Section 602 of the Indenture)

Indemnification of Trustee. Subject to the provisions of the Indenture relating to the duties of the Indenture trustee if an event of default occurs and is continuing, the Indenture trustee will be under no obligation to exercise any of its rights or powers under the Indenture at the request or direction of any of the holders, unless the holders have offered to the Indenture trustee reasonable indemnity. (See Section 603 of the Indenture)

Waiver. The holders of not less than a majority in aggregate principal amount of the outstanding senior debt securities of any series may on behalf of the holders of all senior debt securities of that series waive any default or event of default with respect to that series, except a default or event of default in the payment of the principal of, or premium, if any, or any interest, if any, on any senior debt securities of that series or in respect of a provision that under the Indenture cannot be modified or amended without the consent of the holder of each outstanding senior debt securities of that series affected. (See Section 513 of the Indenture)

Modification of Indenture

We and the Indenture trustee may modify the Indenture, without notice to or the consent of any holders of senior debt securities, with respect to specified matters, including:

If the Trust Indenture Act is amended after the date of the original Indenture in such a way as to require or permit changes to the Indenture, or the elimination of provisions that, at the date of the original Indenture or at any time subsequently were required by the Trust Indenture Act, the Indenture will be automatically amended to conform to the amendment or to make the changes or elimination. The Indenture trustee will, at our request, enter into one or more supplemental indentures with us to evidence or effect the amendment. (See Section 901 of the Indenture)

In addition, we, together with the Indenture trustee, may modify some of our rights and obligations and the rights of holders of the senior debt securities with the consent of the holders of at least a majority in aggregate principal amount of the outstanding senior debt securities of each series affected thereby.

No amendment or modification may, without the consent of each holder of any outstanding senior debt security affected:

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(See Article Nine of the Indenture)

Defeasance

When we use the term defeasance, we mean discharge from some or all of our obligations under the Indenture. If we deposit with the trustee funds or U.S. government obligations the scheduled payments of principal and interest in respect of which is sufficient to make payments of principal of (and premium, if any) and interest on the senior debt securities of a series or tranche thereof on the dates those payments are due and payable, then, at our option, either of the following will occur:

So long as no default or event of default with respect to the senior debt securities of any series has occurred and is continuing, we may affect either a legal defeasance or a covenant defeasance in respect of senior debt securities of that series or tranche by:

(See Section 1304 of the Indenture)

Evidence to be Furnished to the Indenture Trustee

The Indenture provides that we must periodically file statements with the Indenture trustee regarding our compliance with all conditions and covenants of the Indenture. (See Section 704 of the Indenture)

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Concerning the Indenture Trustee

The Bank of New York Mellon Trust Company, N.A., is the Indenture Trustee. We and our affiliates conduct banking transactions with the Indenture trustee in the normal course of business.

Governing Law

The Indenture is governed by and construed in accordance with the laws of the State of New York, without regard to conflict of laws principles, except to the extent that the Trust Indenture Act is applicable.

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BOOK-ENTRY SYSTEM

Unless otherwise specified in the applicable prospectus supplement, each series of securities offered by this prospectus will be issued as fully-registered global securities representing all or part of that series of securities. This means that we will not issue certificates for that series of securities to the holders. Instead, a global security representing that series of securities will be deposited with, or on behalf of, DTC or its successor, as the depository. The global securities will be registered at the request of DTC in the name of Cede & Co., DTC’s nominee, or such other name as may be requested by an authorized representative of DTC.

DTC will keep an electronic record of its participants (for example, your broker) whose clients have purchased securities represented by a global security. Unless a global security is exchanged in whole or in part for a certificated security, a global security may not be transferred, except that DTC, its nominees and successors may transfer a global security as a whole to one another.

Beneficial interests in global securities will be shown on, and transfers of interests will be made only through, records maintained by DTC and its participants. The laws of some jurisdictions require that some purchasers take physical delivery of securities in definitive form. These laws may impair the ability to transfer beneficial interests in a global security.

We will make payments of principal, interest, if any, and premium, if any, to DTC or its nominee. We, the applicable trustee and any paying agent will treat DTC or its nominee as the owner of the global security for all purposes, including any notices and voting. Accordingly, neither we nor any trustee nor any paying agent will have any direct responsibility or liability to pay amounts due on a global security to owners of beneficial interests in a global security.

DTC is a limited-purpose trust company organized under the New York Banking Law, a “banking organization” within the meaning of the New York Banking Law, a member of the Federal Reserve System, a “clearing corporation” within the meaning of the New York Uniform Commercial Code and a “clearing agency” registered pursuant to the provisions of Section 17A of the Exchange Act. DTC holds securities that its participants, or “direct participants,” deposit with DTC. DTC also facilitates the post-trade settlement among direct participants of sales and other securities transactions in deposited securities through electronic computerized book-entry transfers and pledges between direct participants’ accounts. This eliminates the need for physical movement of securities certificates. Direct participants include both U.S. and non-U.S. securities brokers and dealers, banks, trust companies, clearing corporations and certain other organizations. DTC is a wholly owned subsidiary of The Depository Trust & Clearing Corporation, or “DTCC.” DTCC is the holding company for DTC, National Securities Clearing Corporation and Fixed Income Clearing Corporation, all of which are registered clearing agencies. DTCC is owned by the users of its regulated subsidiaries. Access to the DTC system is also available to others such as both U.S. and non-U.S. securities brokers and dealers, banks, trust companies and clearing corporations that clear through or maintain a custodial relationship with a direct participant either directly or indirectly, an “indirect participant.” Direct participants and indirect participants are referred to collectively as “participants.” The DTC Rules applicable to its participants are on file with the SEC.

Purchases of global securities under the DTC system must be made by or through direct participants, which will receive a credit for the securities on DTC’s records. The ownership interest of each actual purchaser of each security, or “beneficial owner,” is in turn to be recorded on the direct and indirect participants’ records. Beneficial owners will not receive written confirmation from DTC of their purchase. Beneficial owners are, however, expected to receive written confirmations providing details of the transaction, as well as periodic statements of their holdings, from the direct or indirect participant through which the beneficial owner entered into the transaction. Transfers of ownership interests in the global securities are to be accomplished by entries made on the books of direct and indirect participants acting on behalf of beneficial owners. Beneficial owners will not receive certificates representing their ownership interests in the global securities, except in the event that use of the book-entry system for the global securities is discontinued.

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To facilitate subsequent transfers, all securities deposited by direct participants with DTC are registered in the name of Cede & Co. or such other name as may be requested by an authorized representative of DTC. The deposit of securities with DTC and their registration in the name of Cede & Co. or such other nominee do not effect any change in beneficial ownership. DTC has no knowledge of the actual beneficial owners of the securities. DTC’s records reflect only the identity of the direct participants to whose accounts such securities are credited, which may or may not be the beneficial owners. The direct and indirect participants remain responsible for keeping account of their holdings on behalf of their customers.

Conveyance of notices and other communications by DTC to direct participants, by direct participants to indirect participants and by direct participants and indirect participants to beneficial owners will be governed by arrangements among them, subject to any statutory or regulatory requirements as may be in effect from time to time.

If a particular series of securities is redeemable at our option or at the option of the holder, redemption notices will be sent to DTC. If less than all of the securities of a series are being redeemed, DTC’s practice is to determine by lot the amount of the interest of each direct participant in such series to be redeemed. Redemption proceeds and distributions on global securities will be made to Cede & Co. or such other nominee as may be requested by an authorized representative of DTC. Upon DTC’s receipt of funds and corresponding detail information from us, any trustee or any paying agent, DTC’s practice is to credit direct participants’ accounts in accordance with the holdings information shown on DTC’s records on the payment date. Payments by participants to beneficial owners of securities will be governed by standing instructions and customary practices, as is the case with securities held for the accounts of customers in bearer form or registered in “street name.” Payments will be the responsibility of such participant and not of DTC nor its nominee, any trustee, any paying agent or us, subject to any statutory or regulatory requirements. Payment of redemption proceeds and distributions to Cede & Co. or such other nominee as may be requested by an authorized representative of DTC is the responsibility of us, the applicable trustee or the applicable paying agent, disbursement of such payments to direct participants will be the responsibility of DTC, and disbursement of such payments to the beneficial owners will be the responsibility of direct and indirect participants.

Neither DTC nor Cede & Co. or any other DTC nominee will consent or vote with respect to global securities unless authorized by a direct participant in accordance with DTC’s procedures. Under its usual procedures, DTC mails an omnibus proxy to us as soon as possible after the record date. The omnibus proxy assigns Cede & Co.’s consenting or voting rights to those direct participants to whose accounts the securities are credited on the record date as identified in a listing attached to the omnibus proxy.

Global securities will be exchangeable for corresponding certificated securities registered in the name of persons other than DTC or its nominee if (1) DTC (a) notifies us that it is unwilling or unable to continue as depository for any of the global securities or (b) at any time ceases to be a clearing agency registered under the Exchange Act, (2) an event of default occurs and is continuing with respect to the applicable series of securities or (3) we execute and deliver to the applicable trustee an order that the global securities will be so exchangeable.

The information in this section concerning DTC and DTC’s book-entry system has been obtained from DTC, and we and any underwriters, dealers or agents are not responsible for the accuracy of the information or for the performance by DTC of its obligations under the rules and procedures governing its operations or otherwise.

Any underwriters, dealers or agents of any securities may be direct participants of DTC.

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PLAN OF DISTRIBUTION

We may sell the securities offered under this prospectus through underwriters or dealers, through agents or directly to one or more purchasers. The terms under which the securities are offered and the method of distribution will be set forth in the applicable prospectus supplement.

Underwriters, dealers and agents that participate in the distribution of the securities offered under this prospectus may be underwriters as defined in the Securities Act of 1933, as amended, the “Securities Act,” and any discounts or commissions received by them from us and any profit on the resale of the offered securities by them may be treated as underwriting discounts and commissions under the Securities Act. Any underwriters or agents will be identified and their compensation, including any underwriting discount or commission, will be described in the applicable prospectus supplement. The applicable prospectus supplement will also describe other terms of the offering, including the initial public offering price and any discounts or concessions allowed or reallowed to dealers.

The distribution of the securities described in this prospectus may be effected from time to time in one or more transactions at a fixed price or prices, which may be changed, at market prices prevailing at the time of sale, at prices related to the prevailing market prices or at negotiated prices.

We may determine the price or other terms of the securities offered under this prospectus by use of an electronic auction. We will describe in the applicable prospectus supplement how any auction will be conducted to determine the price or any other terms of the securities, how potential investors may participate in the auction and, where applicable, the nature of the underwriters’ obligations with respect to the auction.

Each series of securities will be a new issue of securities and will have no established trading market. Any underwriters to whom securities are sold for public offering and sale may make a market in such securities, but such underwriters will not be obligated to do so and may discontinue any market making at any time without notice. The securities may or may not be listed on a national securities exchange.

Under agreements into which we may enter in connection with the sale of the securities, underwriters, dealers and agents who participate in the distribution of the securities may be entitled to indemnification by us against specified liabilities, including liabilities under the Securities Act.

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LEGAL OPINIONS

Unless otherwise indicated in the applicable prospectus supplement, legal opinions relating to the validity of the securities being offered by this prospectus and certain other matters will be rendered by Faegre Baker Daniels LLP, Denver, Colorado, counsel for our company. Unless otherwise indicated in the prospectus supplement relating to a particular series of securities, certain legal matters will be passed upon for the underwriters, dealers or agents named in a prospectus supplement by Hunton Andrews Kurth LLP, New York, New York.

EXPERTS

The consolidated financial statements, and the related financial statement schedule, incorporated in this prospectus by reference from Public Service Company of Colorado’s Annual Report on Form 10-K have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their report, which is incorporated herein by reference. Such consolidated financial statements and financial statement schedule have been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

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PROSPECTUS

SOUTHWESTERN PUBLIC SERVICE

COMPANY

(a New Mexico corporation)

790 South Buchanan Street

Amarillo, Texas 79101

(303) 571-7511

FIRST MORTGAGE BONDS

SENIOR UNSECURED DEBT SECURITIES

We may offer and sell from time to time, in one or more offerings, together or separately, any combination of the securities listed above and described in this prospectus. We may offer and sell these securities to or through one or more underwriters, dealers and/or agents, or directly to purchasers, on a continuous or delayed basis.

This prospectus describes some of the general terms that may apply to the securities and the general manner in which they may be offered. The specific terms of any securities to be offered, and the specific manner in which they may be offered, will be described in a supplement to this prospectus. This prospectus may not be used to sell securities unless accompanied by a prospectus supplement.

You should carefully consider the risk factors set forth in the applicable prospectus supplement and certain of our filings with the Securities and Exchange Commission before making any decision to invest in any of the securities described in this prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is April 18, 2018.

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ABOUT THIS PROSPECTUS

This document is called a “prospectus” and it provides you with a general description of the securities we may offer. Each time we sell securities under this prospectus, we will provide a prospectus supplement containing specific information about the terms of the securities being offered. That prospectus supplement may include a discussion of any risk factors or other special considerations that apply to those securities. The prospectus supplement may also add, update or change the information in this prospectus. If there is any inconsistency between the information in this prospectus and in the prospectus supplement, you should rely on the information in the prospectus supplement. You should read this prospectus and the applicable prospectus supplement together with the additional information described under the caption “Where You Can Find More Information.” We may also prepare free writing prospectuses that describe particular securities. Any free writing prospectus should also be read in connection with this prospectus and with the prospectus supplement referred to therein. For purposes of this prospectus, any reference to an applicable prospectus supplement may also refer to a free writing prospectus, unless the context otherwise requires.

This prospectus is part of a registration statement that we filed with the Securities and Exchange Commission, or the “SEC,” using a shelf registration process. As permitted by SEC rules, this prospectus does not contain all of the information included in the registration statement and the accompanying exhibits and schedules we filed with the SEC. You should read the registration statement and the related exhibits and schedules for more information about us and our securities. The registration statement and the related exhibits and schedules can be read at the SEC’s website or at the SEC’s offices. The SEC’s website and street addresses are provided under the caption “Where You Can Find More Information.”

The distribution of this prospectus and the applicable prospectus supplement and the offering of the securities in certain jurisdictions may be restricted by law. Persons into whose possession this prospectus and the applicable prospectus supplement come should inform themselves about and observe any such restrictions. This prospectus and the applicable prospectus supplement do not constitute, and may not be used in connection with, an offer or solicitation by anyone in any jurisdiction in which such offer or solicitation is not authorized or in which the person making such offering or solicitation is not qualified to do so or to any person to whom it is unlawful to make such offer or solicitation.

This prospectus, the applicable prospectus supplement and any free writing prospectus that we prepare or authorize contain and incorporate by reference information that you should consider when making your investment decision. No one is authorized to provide you with information different from that which is contained, or deemed to be contained, in this prospectus and applicable prospectus supplement. We are not making an offer of these securities in any jurisdiction where the offer is not permitted. You should not assume that the information in this prospectus or the documents incorporated by reference is accurate as of any date other than the date on the front of those documents.

Unless otherwise specified or unless the context requires otherwise, all references in this prospectus to “Southwestern Public Service Company,” “SPS,” “our company,” “we,” “us,” or similar terms refers to Southwestern Public Service Company.

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WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and current reports and other information with the SEC. Our SEC filings are available to the public on the SEC’s website at http://www.sec.gov. You may also read and copy any document we file with the SEC at the SEC’s Public Reference Room located at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information on the Public Reference Room.

The SEC allows us to “incorporate by reference” the information we file with it, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is an important part of this prospectus, and information that we file later with the SEC will automatically update and supersede this information. We incorporate by reference our Annual Report on Form 10-K for the year ended December 31, 2017, including information specifically incorporated by reference into our Form 10-K from Xcel Energy Inc.’s definitive Proxy Statement for its 2018 Annual Meeting of Shareholders, and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, or the “Exchange Act,” (other than information deemed to have been “furnished” rather than “filed” in accordance with SEC rules) from the date of this prospectus until we sell all of the securities offered by this prospectus (other than, in each case, documents or information deemed to have been furnished and not filed in accordance with SEC rules).

We will provide, without charge, to each person, including any beneficial owner of our securities to whom this prospectus is delivered, upon written or oral request, a copy of any or all documents referred to above that have been incorporated by reference into this prospectus, excluding exhibits to those documents unless they are specifically incorporated by reference into those documents. You may request these documents from:

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OUR COMPANY

We were incorporated in 1921 under the laws of the State of New Mexico. We are a utility engaged primarily in the generation, purchase, transmission, distribution and sale of electricity in portions of Texas and New Mexico. At December 31, 2017, we provided electric utility service to approximately 390,000 retail customers in Texas and New Mexico.

Our principal executive offices are located at 790 South Buchanan Street, Amarillo, Texas 79101 and our telephone number is (303) 571-7511.

DESCRIPTION OF THE FIRST MORTGAGE BONDS

The description below contains summaries of selected provisions of the mortgage indenture, including supplemental indentures, under which the first mortgage bonds, which we sometimes refer to as “first mortgage bonds,” “mortgage securities,” or “mortgage bonds,” will be issued. These summaries are not complete. The mortgage indenture and the form of supplemental indenture, including the form of first mortgage bond, applicable to the first mortgage bonds have been filed as exhibits to the registration statement of which this prospectus is a part. You should read them for provisions that may be important to you. In the summaries below, we have included references to section numbers of the mortgage indenture so that you can easily locate these provisions. Certain terms used but not defined in the following summary have the meaning specified in the mortgage indenture.

This section describes the general terms and provisions of our first mortgage bonds. The prospectus supplement will describe the specific terms of the first mortgage bonds offered through that prospectus supplement and any general terms outlined in this section that will not apply to those first mortgage bonds.

General

We may issue the first mortgage bonds from time to time in one or more series under the Indenture dated as of August 1, 2011, as supplemented from time to time by supplemental indentures relating to the first mortgage bonds being offered by this prospectus, which we collectively refer to as the “mortgage indenture,” between us and U.S. Bank National Association, as trustee, which we refer to as the “mortgage trustee.” The mortgage indenture will govern the first mortgage bonds offered by this prospectus.

The amount of mortgage securities that we may issue under the mortgage indenture is unlimited. The mortgage securities may be issued in series up to the aggregate principal amount that may be authorized by us from time to time. Although the mortgage indenture does not limit the amount of mortgage securities that we may issue under it, we may only issue mortgage securities under the mortgage indenture on the basis of property additions, retired mortgage securities or cash (as discussed below). See “—Issuance of Additional Mortgage Securities” for more information about the limitations on the issuance of mortgage securities.

The holders of outstanding first mortgage bonds do not, and, unless the prospectus supplement that describes a particular series of first mortgage bonds provides otherwise with respect to that series, the holders of any first mortgage bonds offered by this prospectus will not, have the right to require us to repurchase the first mortgage bonds if we become involved in a highly leveraged or change of control transaction. The mortgage indenture does not have any provision that is designed specifically in response to highly leveraged or change of control transactions. However, holders of first mortgage bonds would have the security afforded as described below under the caption “—Security.”

When we offer to sell a particular series of first mortgage bonds, we will describe the specific terms of that series in a prospectus supplement relating to that series, including the following terms:

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