Exhibit 4.1

WESTAR ENERGY, INC.

TO

BNY MIDWEST TRUST COMPANY

as Trustee

(as Successor to

HARRIS TRUST AND SAVINGS BANK)

THIRTY-SIXTH SUPPLEMENTAL INDENTURE

Dated as of June 1, 2004

First Mortgage Bonds, Pollution Control Refunding Revenue Series Due 2033

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THIRTY-SIXTH SUPPLEMENTAL INDENTURE, dated as of the 1st day of June, Two Thousand and Four, made by and between Westar Energy, Inc., formerly The Kansas Power and Light Company, a corporation organized and existing under the laws of the State of Kansas (hereinafter called the “ Company ”), party of the first part, and BNY Midwest Trust Company, an Illinois trust company whose mailing address is 2 North LaSalle Street, Suite 1020, Chicago, IL 60602 (hereinafter called the “ Trustee ”), as Trustee (as successor to Harris Trust and Savings Bank), under the Mortgage and Deed of Trust dated July 1, 1939, hereinafter mentioned, party of the second part;

WHEREAS, the Company has heretofore executed and delivered to the Trustee its Mortgage and Deed of Trust dated July 1, 1939 (hereinafter referred to as the “ Original Indenture ”), to provide for and to secure the issue of First Mortgage Bonds of the Company, issuable in series, and to declare the terms and conditions upon which the Bonds (as defined in the Original Indenture) are to be issued thereunder; and

WHEREAS, the Company has heretofore executed and delivered to the Trustee Thirty-Five Supplemental Indentures supplemental to said Original Indenture, of which Thirty-Three provided for the issuance thereunder of series of the Company’s First Mortgage Bonds, and there is set forth below information with respect to such Supplemental Indentures as have provided for the issuance of Bonds, and the principal amount of Bonds which remain outstanding as of June 1, 2004.

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; and

WHEREAS, the Company is entitled at this time to have authenticated and delivered additional bonds in substitution for refundable Bonds, upon compliance with the provisions of Article III of the Original Indenture, as amended; and

WHEREAS, the Company desires by this Thirty-Sixth Supplemental Indenture (hereinafter referred to as this “ Supplemental Indenture ”) to supplement the Original Indenture and to provide for the creation of a new series of bonds under the Original Indenture to be designated “First Mortgage Bonds, Pollution Control Refunding Revenue Series Due 2033”(hereinafter called “Bonds

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of the 2033 Series); and the Original Indenture provides that certain terms and provisions, as determined by the Board of Directors of the Company, of the Bonds of any particular series may be expressed in and provided by the execution of an appropriate supplemental indenture; and

WHEREAS, the Company in the exercise of the powers and authority conferred upon and reserved to it under the provisions of the Original Indenture and indentures supplemental thereto, and pursuant to appropriate resolutions of its Board of Directors, has duly resolved and determined to make, execute and deliver to the Trustee a supplemental indenture in the form hereof for the purposes herein provided; and

WHEREAS, all conditions and requirements necessary to make this Thirty-Sixth Supplemental Indenture a valid, binding and legal instrument have been done, performed and fulfilled, and the execution and delivery hereof have been in all respects duly authorized;

NOW, THEREFORE, THIS INDENTURE WITNESSETH: That, in consideration of the premises and of the mutual covenants herein contained and of the sum of One Dollar duly paid by the Trustee to the Company at or before the time of the execution of these presents, and of other valuable considerations, the receipt whereof is hereby acknowledged, and in order further to secure the payment of the principal of and interest and premium, if any, on all Bonds at any time issued and outstanding under the Original Indenture as amended by all indentures supplemental thereto (hereinafter sometimes collectively called the “ Indenture ”) according to their tenor, purport and effect, and to declare certain terms and conditions upon and subject to which Bonds are to be issued and secured, the Company has executed and delivered this Supplemental Indenture, and by these presents grants, bargains, sells, warrants, aliens, releases, conveys, assigns, transfers, mortgages, pledges, sets over and ratifies and confirms unto BNY Midwest Trust Company, as Trustee, and to its successors in trust under the Indenture forever, all and singular the following described properties (in addition to all other properties heretofore specifically subjected to the lien of the Indenture and not heretofore released from the lien thereof), that is to say:

FIRST.

All and singular the rents, real estate, chattels real, easements, servitudes, and leaseholds of the Company, or which, subject to the provisions of Article XII of the Original Indenture, the Company may hereafter acquire, including, among other things, the property described in Appendix A hereto under the caption “First”, which description is hereby incorporated herein by reference and made a part hereof as if fully set forth herein, together with all improvements of any type located thereon.

Also all power houses, plants, buildings and other structures, dams, dam sites, substations, heating plants, gas works, holders and tanks, compressor stations, gasoline extraction plants, together with all and singular the electric heating, gas and mechanical appliances appurtenant thereto of every nature whatsoever, now owned by the Company or which it may hereafter acquire, including all and singular the machinery, engines, boilers, furnaces, generators, dynamos, turbines and motors, and all and every character of mechanical appliance for generating or producing electricity, steam, water, gas and other agencies for light, heat, cold or power or any other purpose whatsoever.

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SECOND.

Also all transmission and distribution systems used for the transmission and distribution of electricity, steam, water, gas and other agencies for light, heat, cold or power, or any other purpose whatever, whether underground or overhead or on the surface or otherwise of the Company, or which, subject to the provisions of Article XII of the Original Indenture, the Company may hereafter acquire, including all poles, posts, wires, cables, conduits, mains, pipes, tubes, drains, furnaces, switchboards, transformers, insulators, meters, lamps, fuses, junction boxes, water pumping stations, regulator stations, town border metering stations and other electric, steam, water and gas fixtures and apparatus.

THIRD.

Also all franchises and all permits, ordinances, easements, privileges and immunities and licenses, all rights to construct, maintain and operate overhead, surface and underground systems for the distribution and transmission of electricity, gas, water or steam for the supply to itself or others of light, heat, cold or power or any other purpose whatsoever, all rights-of-way, all waters, water rights and flowage rights and all grants and consents, now owned by the Company or, subject to the provisions of Article XII of the Original Indenture, which it may hereafter acquire.

Also all inventions, patent rights and licenses of every kind now owned by the Company or, subject to the provisions of Article XII of the Original Indenture, which it may hereafter acquire.

FOURTH.

Also, subject to the provisions of Article XII of the Original Indenture, all other property, real, personal and mixed (except as therein or herein expressly excepted) of every nature and kind and wheresoever situated now or hereafter possessed by or belonging to the Company, or to which it is now, or may at any time hereafter be, in any manner entitled at law or in equity.

FIFTH.

Also any and all property of any kind or description which may from time to time after the date of the Original Indenture by delivery or by writing of any kind be conveyed, mortgaged, pledged, assigned or transferred to the Trustee by the Company or by any person, copartnership or corporation, with the consent of the Company or otherwise, and accepted by the Trustee, to be held as part of the mortgaged property; and the Trustee is hereby authorized to accept and receive any such property and any such conveyance, mortgage, pledge, assignment and transfer, as and for additional security hereunder, and to hold and apply any and all such property subject to and in accordance with the terms and provisions upon which such conveyance, mortgage, pledge, assignment or transfer shall be made.

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SIXTH.

Together with all and singular, the tenements, hereditaments and appurtenances belonging or in any wise appertaining to the aforesaid property or any part thereof, with the reversion and reversions, remainder and remainders, tolls, rents, revenues, issues, income, products and profits thereof, and all the estate, right, title, interest and claim whatsoever, at law and in equity, which the Company now has or may hereafter acquire in and to the aforesaid property and franchises and every part and parcel thereof.

EXPRESSLY EXCEPTING AND EXCLUDING, HOWEVER, all properties of the character excepted from the lien of the Original Indenture.

TO HAVE AND TO HOLD all said properties, real, personal and mixed, mortgaged, pledged and conveyed by the Company as aforesaid, or intended so to be, unto the Trustee and its successors and assigns forever;

SUBJECT, HOWEVER, to the exceptions and reservations hereinabove referred to, to existing leases other than leases which by their terms are subordinate to the lien of the Indenture, to existing liens upon rights-of-way for transmission or distribution line purposes, as defined in Article I of the Original Indenture; and any extensions thereof, and subject to existing easements for streets, alleys, highways, rights-of-way and railroad purposes over, upon and across certain of the property herein before described and subject also to all the terms, conditions, agreements, covenants, exceptions and reservations expressed or provided in the deeds or other instruments respectively under and by virtue of which the Company acquired the properties hereinabove described and to undetermined liens and charges, if any, incidental to construction or other existing permitted liens as defined in Article I of the Original Indenture;

IN TRUST, NEVERTHELESS, upon the terms and trusts in the Original Indenture, and the indentures supplemental thereto, including this Supplemental Indenture, set forth, for the equal and proportionate benefit and security of all present and future holders of the Bonds and coupons issued and to be issued thereunder, or any of them, without preference of any of said Bonds and coupons of any particular series over the Bonds and coupons of any other series by reason of priority in the time of issue, sale or negotiation thereof, or by reason of the purpose of issue or otherwise howsoever, except as otherwise provided in Section 2 of Article IV of the Original Indenture.

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AND IT IS HEREBY COVENANTED, DECLARED AND AGREED, by and between the parties hereto for the benefit of those who shall hold the Bonds and coupons, or any of them, to the be issued under the Indenture as follows:

ARTICLE I

DESCRIPTION OF BONDS OF THE

2033 SERIES

SECTION 1. The 2033 series of Bonds to be executed, authenticated and delivered under and secured by the Original Indenture shall be designated as “First Mortgage Bonds, Pollution Control Refunding Revenue Series Due 2033” of the Company (herein called “ Bonds of the 2033 Series ”). The Bonds of the 2033 Series shall be executed, authenticated and delivered in accordance with the provisions of, and shall in all respects be subject to, all of the terms, conditions and covenants of the Original Indenture, as amended, and subject to all the terms, conditions and covenants of this Supplemental Indenture.

Bonds of the 2033 Series shall mature February 1, 2033 and shall bear from time to time interest at a rate equal to the interest rate then borne by the City of Wamego, Kansas, Pollution Control Refunding Revenue Bonds (Westar Energy, Inc. Project) Series 2004 (hereinafter referred to as “Revenue Bonds”), issued pursuant to the Indenture of Trust, dated as of June 1, 2004 (hereinafter referred to as the “Revenue Bond Indenture”), from the City of Wamego, Kansas, to Deutsche Bank Trust Company Americas, as trustee thereunder (the “Revenue Bond Trustee”) which rate shall initially be five percent (5.00%) per annum, payable at the same times as interest is payable on the Revenue Bonds, initially semi-annually on the first day of February and August in each year, commencing February 1, 2005. Every Bond of the 2033 Series shall be dated the date of authentication except that, notwithstanding the provisions of Section 6 of Article II of the Original Indenture, if any Bond of the 2033 Series shall be authenticated at any time subsequent to the record date (as hereinafter in this Section defined) for any interest payment date but prior to the day following such interest payment date, it shall be dated as of the day following such interest payment date, provided, however, if at the time of authentication of any Bond of the 2033 Series interest shall be in default on any Bonds of the 2033 Series, such Bond shall be dated as of the day following the interest payment date to which interest has previously been paid in full or made available for payment in full on outstanding Bonds of the 2033 Series, as the case may be, or, if no interest has been paid or made available for payment, as of the date of initial authentication and delivery of such Bond. Every Bond of the 2033 Series shall bear interest from the February 1, or August 1, next preceding the date thereof, unless such Bond shall be dated prior to February 1, 2005, in which case it shall bear interest from June 1, 2004; provided, that if interest is no longer payable on February 1 and August 1 then from the interest payment date next preceding the date thereof.

The person in whose name any Bond of the 2033 Series is registered at the close of business on any record date with regard to any interest payment date shall be entitled to receive the interest payable thereon on such interest payment date notwithstanding the cancellation of such Bond upon the transfer or exchange thereof subsequent to such record date and prior to the day following such interest payment date, unless the Company shall default in the payment of the interest due on such interest payment date, in which case such defaulted interest shall be paid to the person in whose name such Bond is registered on the date of payment of such defaulted interest. The term “ record date ” as used in this Section shall mean the close of business on the record date for the Revenue Bonds pursuant

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to the Revenue Bond Indenture. The Bonds of the 2033 Series shall be payable as to principal, premium, if any, and interest, in any coin or currency of the United States of America which at the time of payment is legal tender for public and private debts, at the agency of the Company in the City of Chicago, Illinois, or at the option of the holder thereof at the agency of the Company in the Borough of Manhattan, The City of New York, provided that at the option of the Company interest may be paid by check mailed to the holder at such holder’s registered address.

The obligation of the Company to make payments with respect to the principal of and premium, if any, and interest on Bonds of the 2033 Series shall be fully or partially, as the case may be, satisfied and discharged (1) to the extent that the then due payments with respect to the principal and premium, if any, and interest on the Revenue Bonds (other than Revenue Bonds which have been redeemed or called for redemption, or which have been surrendered in lieu of, in substitution for or in exchange for other Revenue Bonds or surrendered upon registration of transfer of Revenue Bonds to the Revenue Bond Indenture) shall have been fully or partially satisfied and discharged, and (2) to the extent that at the time any payment of principal or premium, if any, or interest on the Revenue Bond becomes due, either at or before maturity, there shall be in the Bond Fund established pursuant to the Revenue Bond Indenture sufficient cash (whether received by the Revenue Bond Trustee under the Sublease dated as of June 1, 2004, (the “Sublease”), between the City of Wamego, Kansas, and the Company, or otherwise) available to pay the principal of and premium, if any, and interest on the Revenue Bonds then due. The obligation of the Company to make payments with respect to the principal of and premium, if any, and interest on the Bonds of the 2033 Series shall also be satisfied and discharged at such time pursuant to the provisions of Article X of the Revenue Bond Indenture, the principal and premium, if any, and interest on the Revenue Bonds has been paid or the Revenue Bond Trustee shall hold moneys or Investment Obligations (meeting the requirements of such Article X) sufficient to pay the principal of and premium, if any, and interest on the Revenue Bonds and to the extent in such Article X provided, and provision for paying all other sums required by such Article X shall have been made. In this case, the entire principal amount of the Bonds of the 2033 Series then outstanding shall be deemed to be satisfied and discharged. Neither the invalidity nor the unenforceability, in whole or in part, of the Sublease or any provision thereof (whether by reason of bankruptcy or otherwise) shall impair or limit the obligation of the Company to pay the principal of and premium, if any, and interest on the Bonds of the 2033 Series when and as they become due and payable. The Trustee may conclusively presume that the obligation of the Company to make payment with respect to the principal of and premium, if any, and interest on the Bonds of the 2033 Series shall have been satisfied and discharged unless and until the Trustee shall have received a written notice from the Revenue Bond Trustee stating (i) that timely payment of the principal of or premium, if any, or interest on the Revenue Bonds has not been made, (ii) that there are not sufficient available funds in such Bond Fund to make such payment and (iii)the amount of funds required to make such payment.

SECTION 2. The Bonds of the 2033 Series shall be registered bonds without coupons of the denominations of $5,000 and of any multiples of $5,000, numbered consecutively from R 1 upwards. Bonds of the 2033 Series may each be interchanged for each other bonds within a respective Series in authorized denominations and in the same aggregate principal amounts, without charge, except for any tax or governmental charge imposed in connection with such interchange.

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SECTION 3. The Bonds of the 2033 Series, and the Trustee’s Certificate with respect thereto, shall be substantially in the following forms, respectively:

[FORM OF BOND OF THE 2033 SERIES]

CUSIP             

WESTAR ENERGY, INC.

(Incorporated under the laws of the State of Kansas)

FIRST MORTGAGE BOND, POLLUTION CONTROL REFUNDING REVENUE SERIES DUE 2033

DUE February 1, 2033

WESTAR ENERGY, INC., a corporation organized and existing under the laws of the State of Kansas (hereinafter called the “ Company ”, which term shall include any successor entity as defined in the Indenture hereinafter referred to), for value received, hereby promises to pay to              or registered assigns, on the 1st day of February, 2033, the sum of              Dollars in any coin or currency of the United States of America which at the time of payment is legal tender for public and private debts, and to pay interest thereon in like coin or currency from the first day of February or August next preceding the date of this Bond (or the interest payment date next preceding the date hereof, if different from February 1 or August 1), unless no interest has been paid on this Bond, in which case from June 1, 2004, at a rate equal to the interest rate then borne by the City of Wamego, Kansas, Pollution Control Refunding Revenue Bonds (Westar Energy, Inc. Project) Series 2004 (hereinafter referred to as “ Revenue Bonds ”), issued pursuant to the Indenture of Trust, dated as of June, 1 2004 (hereinafter referred to as the “ Revenue Bond Indenture ”), from the City of Wamego, Kansas, to Deutsche Bank Trust Company Americas, as trustee thereunder (the “ Revenue Bond Trustee ”) which rate shall initially be five percent (5.00%) per annum, payable semiannually, on the first days of February and August in each year, commencing February 1, 2005, or as otherwise provided in the Indenture, until maturity, or, if this Bond shall be duly called for redemption or submitted for repurchase, until the redemption date or repurchase date, as the case may be, or, if the Company shall default in the payment of the principal or premium hereof, until the Company’s obligation with respect to the payment of such principal or premium shall be discharged as provided in the Indenture hereinafter mentioned. The interest payable on any interest payment date as aforesaid will be paid to the person in whose name this Bond is registered at the close of business on the record date for the Revenue Bonds pursuant to the Revenue Bond Indenture (the “ record date ”), unless the Company shall default in the payment of the interest due on such interest payment date, in which case such defaulted interest shall be paid to the person in whose name this Bond is registered on the date of payment of such defaulted interest. Principal of, premium, if any, and interest on, this Bond are payable at the agency of the Company in the City of Chicago, Illinois in immediately available funds or at the option of the holder thereof at the agency of the Company in the Borough of Manhattan, The City of New York, provided that at the option of the Company interest may be paid by check mailed to the holder at such holder’s registered address.

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The obligation of the Company to make payments with respect to the principal of and premium, if any, and interest on Bonds of this Series shall be satisfied and discharged (1) to the extent that the then due payments with respect to the principal and premium, if any, and interest on the Revenue Bonds (other than Revenue Bonds which have been redeemed or called for redemption, or which have been surrendered in lieu of, in substitution for or in exchange for other Revenue Bonds or surrendered upon registration of transfer of Revenue Bonds to the Revenue Bond Indenture), shall have been fully or partially satisfied and discharged, and (2) to the extent that at the time any payment of principal or premium, if any, or interest on the Revenue Bond becomes due, either at or before maturity, there shall be in the Bond Fund established pursuant to the Revenue Bond Indenture sufficient cash (whether received by the Revenue Bond Trustee under the Sublease dated as of June 1, 2004, (the “Sublease”), between the City of Wamego, Kansas, and the Company, or otherwise) available to pay the principal of and premium, if any, and interest on the Revenue Bonds then due, and (3) at such time pursuant to the provisions of Article X of the Revenue Bond Indenture, the principal and premium, if any, and interest on the Revenue Bonds has been paid or the Revenue Bond Trustee shall hold moneys or Investment Obligations (meeting the requirements of such Article X) sufficient to pay the principal of and premium, if any, and interest on the Revenue Bonds and to the extent in such Article X provided, and provision for paying all other sums required by such Article X shall have been made.

This Bond is one of a duly authorized issue of Bonds of the Company (herein called the “ Bonds ”), in unlimited aggregate principal amount, of the series hereinafter specified, all issued and to be issued under and equally secured by a Mortgage and Deed of Trust, dated July 1, 1939, executed by the Company to BNY Midwest Trust Company (herein called the “ Trustee ”), as Trustee (as successor to Harris Trust and Savings Bank), as amended by the indentures supplemental thereto including the thirty-sixth indenture supplemental thereto dated as of June 1, 2004 (herein called the “ Supplemental Indenture ”), between the Company and the Trustee (said Mortgage and Deed of Trust, as so amended, being herein called the “ Indenture ”), to which Indenture and all indentures supplemental thereto reference is hereby made for a description of the properties mortgaged and pledged, the nature and extent of the security, the rights of the bearers or registered owners of the Bonds and of the Trustee in respect thereto, and the terms and conditions upon which the Bonds are, and are to be, secured. The Bonds may be issued in series, for various principal sums, may mature at different times, may bear interest at different rates and may otherwise vary as in the Indenture provided. This Bond is one of a series designated as the “First Mortgage Bonds, Pollution Control Refunding Revenue Series Due 2033” (herein called “ Bonds of the 2033 Series ”) of the Company, issued under and secured by the Indenture executed by the Company to the Trustee.

To the extent permitted by, and as provided in the Indenture, modifications or alterations of the Indenture or of any indenture supplemental thereto, and of the rights and obligations of the Company and of the holders of the Bonds and coupons, may be made with the consent of the Company by an affirmative vote of not less than 60% in principal amount of the Bonds entitled to vote then outstanding, at a meeting of Bondholders called and held as provided in the Indenture, and

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by an affirmative vote of not less than 60% in principal amount of the Bonds of any series entitled to vote then outstanding and affected by such modification or alteration, in case one or more but less than all of the series of Bonds then outstanding under the Indenture are so affected. No modification or alteration shall be made which will affect the terms of payment of the principal of or premium, if any, or interest on, this Bond, which are unconditional. The Company has reserved the right to make certain amendments to the Indenture, without any consent or other action by holders of the Bonds of this series (i) to the extent necessary from time to time to qualify the Indenture under the Trust Indenture Act of 1939, (ii) to delete the requirement that the Company meet a net earnings test as a condition to authenticating additional Bonds or merging into another company and (iii) to make certain other amendments which make the provisions for the release of mortgaged property less restrictive, all as more fully provided in the Indenture and in the Supplemental Indenture. In addition, once all Bonds issued prior to January 1, 1997 are no longer outstanding, the Company will be permitted to issue additional Bonds in an amount equal to 70% of the value of net bondable property additions not subject to an unfunded prior lien, as provided in the Original Indenture.

The Bonds of the 2033 Series are subject to immediate redemption in whole, at the principal amount thereof, but without premium, together with accrued interest to the redemption date, upon receipt by the Trustee of a written demand from the Revenue Bond Trustee stating that the principal amount of all the Revenue Bonds then outstanding under the Revenue Bond Indenture has been declared immediately due and payable pursuant to Section 7.2 of the Revenue Bond Indenture and that the Revenue Bond Trustee, as holder of all of the Bonds of the 2033 Series, waives notice of such redemption. As in the Indenture provided, such notice of redemption will be rescinded and become null and void for all purposes under the Indenture upon rescission of the aforesaid written demand under the Revenue Bond Indenture, and thereupon no such redemption of the Bonds of the 2033 Series will be made.

The Bonds of the 2033 Series are also subject to mandatory redemption, (i) either as a whole or in part, at any time, upon receipt by the Company of a written notice pursuant to paragraph (a) of Section 3.1 of the Revenue Bond Indenture, and (ii) in such principal amounts and on such dates as Revenue Bonds are subject to redemption pursuant to paragraph (b) of Section 3.1 of the Revenue Bond Indenture. Bonds of the 2033 Series equal in principal amount to the principal amount of such Revenue Bonds to be redeemed will be redeemed on the date fixed for redemption of the Revenue Bonds upon payment of the principal amount thereof, but without premium, together with accrued interest to the redemption date.

In addition, Bonds of the 2033 Series are subject to redemption upon payment of the principal amount thereof, together with accrued interest to the redemption date, and premium, if any, (i) in such principal amounts and on such dates as Revenue Bonds are subject to redemption pursuant to Section 3.2 of the Revenue Bond Indenture, (ii) in such principal amounts and on such dates as the Revenue Bonds are subject to redemption pursuant to Section 3.3 of the Revenue Bond Indenture, (iii) in such principal amounts and on such dates as Revenue Bonds are subject to redemption pursuant to Section 3.4 of the Revenue Bond Indenture, (iv) in such principal amounts and on such dates as Revenue Bonds are subject to redemption pursuant to Section 3.5 of the Revenue Bond Indenture, and (v) in such principal amounts and on such dates as Revenue Bonds are subject to redemption pursuant to

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Section 3.6 of the Revenue Bond Indenture. Upon receipt by the Trustee of written notice from the Revenue Bond Trustee that a stated principal amount of Revenue Bonds has been called for redemption pursuant to any of such provisions, stating the redemption date and the redemption price therefor, and that the Revenue Bond Trustee, as holder of all of the Bonds of the 2033 Series, waives notice, Bonds of the 2033 Series shall be redeemed on the same date in the same principal amount and at the same redemption price as the Revenue Bonds.

The Company or a successor entity may deliver to the Trustee in substitution for any Bonds of the 2033 Series, mortgage bonds or other similar instruments as set forth in Article III, Section [6] of the Supplemental Indenture.

In case an event of default, as defined in the Indenture, shall occur, the principal of all of the Bonds at any such time outstanding under the Indenture may be declared or may become due and payable, upon the conditions and in the manner and with the effect provided in the Indenture. The Indenture provides that such declaration may in certain events be waived by the holders of a majority in principal amount of the Bonds outstanding.

This Bond is transferable by the registered owner hereof, in person or by duly authorized attorney, on the books of the Company to be kept for that purpose at the agency of the Company in the City of Chicago, Illinois, and at the agency of the Company in the Borough of Manhattan, The City of New York, upon surrender and cancellation of this Bond and on presentation of a duly executed written instrument of transfer, and thereupon a new registered Bond or Bonds of the same series, of the same aggregate principal amount and in authorized denominations will be issued to the transferee or transferees in exchange herefor; and this Bond, with or without others of like form and series, may in like manner be exchanged for one or more new registered Bonds of the same series of other authorized denominations but of the same aggregate principal amount; all upon payment of the charges and subject to the terms and conditions set forth in the Indenture.

No recourse shall be had for the payment of the principal of or premium, if any, or interest on this Bond, or for any claim based hereon or on the Indenture or any indenture supplemental thereto, against any incorporator, or against any stockholder, director or officer, past, present or future, of the Company, or of any predecessor or successor entity, as such, either directly or through the Company or any such predecessor or successor entity, whether by virtue of any constitution, statute or rule of law, or by the enforcement of any assessment or penalty or otherwise, all such liability, whether at common law, in equity, by any constitution, statute or otherwise, of incorporators, stockholders, directors or officers being released by every owner hereof by the acceptance of this Bond and as part of the consideration for the issue hereof, and being likewise released by the terms of the Indenture.

No director, officer, employee or stockholder of the Company will have any liability for any obligations of the Company under the Bonds or Indenture or for any claim based on, in respect of, or by reason of, such obligations or their creation. Each holder by accepting a Bond waives and releases all such liability. The waiver and release are part of the consideration for issuance of the Bonds. The waiver may not be effective to waive liabilities under the federal securities laws. It is the view of the Securities and Exchange Commission that this type of waiver is against public policy.

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This Bond shall not be entitled to any benefit under the Indenture or any indenture supplemental thereto, or become valid or obligatory for any purpose, until BNY Midwest Trust Company, the Trustee (as successor to Harris Trust and Savings Bank) under the Indenture, or a successor trustee thereto under the Indenture, shall have signed the form of certificate endorsed hereon.

IN WITNESS WHEREOF, WESTAR ENERGY, INC. has caused this Bond to be signed in its name by its Chairman of the Board, President and Chief Executive Officer or a Vice President, manually or by facsimile, and its corporate seal (or a facsimile thereof) to be hereto affixed and attested by its Secretary or an Assistant Secretary, manually or by facsimile.

Dated:

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[FORM OF TRUSTEE’S CERTIFICATE]

This Bond is one of the Bonds, of the series designated herein, described in the within-mentioned Mortgage and Deed of Trust of July 1, 1939 and Supplemental Indenture dated as of June 1, 2004.

SECTION 4. Until Bonds of the 2033 Series in definitive form are ready for delivery, the Company may execute, and upon its request in writing the Trustee shall authenticate and deliver, in lieu thereof, Bonds of the 2033 Series in temporary form, as provided in Section 9 of Article II of the Original Indenture.

ARTICLE II

ISSUE OF BONDS OF THE 2033 SERIES

SECTION 1. The total principal amount of Bonds of the 2033 Series which may be authenticated and delivered hereunder is not limited except as the Original Indenture and this Supplemental Indenture limit the principal amount of Bonds which may be issued thereunder.

SECTION 2. Bonds of the 2033 Series for the aggregate principal amount of $58,340,000 may forthwith be executed by the Company and delivered to the Trustee and shall be authenticated by the Trustee and delivered (either before or after the filing or recording hereof) to or upon the order of the Company, upon receipt by the Trustee of the resolutions, certificates, instruments and opinions required by Article III and Article XVIII of the Original Indenture, as amended.

ARTICLE III

REDEMPTION AND SUBSTITUTION

SECTION 1. Upon the redemption, in whole or in part, of the Revenue Bonds, Bonds of the 2033 Series shall be redeemed in whole or in like part. To effect the redemption of Bonds of the 2033 Series, the Revenue Bond Trustee shall deliver to the Corporate Trustee (and mail a copy thereof to the Company) a written demand (hereinafter referred to as a “Redemption Demand”) for the redemption of Bonds of the 2033 Series equal in principal amount to the principal amount of the Revenue Bonds to be redeemed. The Redemption Demand shall be signed by the President, a Vice President, an Assistant Vice President or a Trust Officer of the Revenue Bond Trustee and shall state: (1) the aggregate principal amount of the Revenue Bonds then outstanding under the Indenture of Trust; (2) the principal amount of the Revenue Bonds to be redeemed; (3) the interest thereon and

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premium, if any, to be payable on the redemption date; (4) the redemption date and that notice thereof has been given as required in the Revenue Bond Indenture; and (5) that the Corporate Trustee is thereby instructed to call for redemption of Bonds of the 2033 Series equal in principal amount to the principal amount of the Revenue Bonds specified in (2) above. The Redemption Demand shall also contain a waiver of notice of such redemption by the Revenue Bond Trustee, as holder of all Bonds of the 2033 Series then outstanding. The Corporate Trustee may conclusively presume the statements contained in the Wamego Redemption Demand to be correct. Redemption of the Bonds of the 2033 Series shall be at the principal amount of the bonds to be redeemed, together with premium, if any, and the accrued interest to the redemption date, and such amount shall become and be due and payable on the redemption date. The Company hereby covenants that, if a Redemption Demand shall be delivered to the Corporate Trustee, the Company, on or before the redemption date, with the Corporate Trustee, in accordance with Article V of the Original Indenture, an amount in cash sufficient to redeem the Bonds of the 2033 Series so called for redemption.

SECTION 2. The Bonds of the 2033 Series are subject to immediate redemption in whole, at the principal amount thereof, but without premium, together with accrued interest to the redemption date, upon receipt by the Trustee of a written demand from the Revenue Bond Trustee stating that the principal amount of all the Revenue Bonds then outstanding under the Revenue Bond Indenture has been declared immediately due and payable pursuant to Section 7.2 of the Revenue Bond Indenture and that the Revenue Bond Trustee, as holder of all of the Bonds of the 2033 Series, waives notice of such redemption. Such notice of redemption will be rescinded and become null and void for all purposes under the Indenture upon rescission of the aforesaid written demand under the Revenue Bond Indenture, and thereupon no such redemption of the Bonds of the 2033 Series will be made.

SECTION 3. The provisions of Article V of the Original Indenture shall be applicable to the redemptions of Bonds of the 2033 Series pursuant to provisions of Section 1 or 2 of this Article III; provided, however, that, with respect to any redemption of Bonds of the 2033 Series pursuant to such Section 1 or 2 an election to redeem shall be made in the manner provided in such Section 1 or 2, respectively. The principal amount of the Bonds of the 2033 to be redeemed on any partial redemption shall be $5,000 or a multiple thereof.

SECTION 4. Any Bonds of the 2033 Series redeemed pursuant to Section 1 or 2 of this Article III are hereby expressly permitted to be used as refundable Bonds for execution, authentication and delivery of additional Bonds pursuant to Section 6 of Article III of the Original Indenture.

SECTION 5. Any written notice to the Trustee from the Revenue Bond Trustee shall be signed by an officer of the Revenue Bond Trustee duly authorized by such purpose.

SECTION 6. The Company may deliver to the Trustee in substitution for any Bonds of the 2033 Series, mortgage bonds or other similar instruments of the Company or any successor entity, whether by merger, combination or acquisition of all or substantially all of the assets of the Company, or otherwise, issued under a mortgage and deed of trust or similar instrument of the Company or any successor entity in like principal amount of like term and bearing the same rate of interest as the Bonds of the 2033 Series (such substituted bonds hereinafter being referred to as the “Substituted

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Mortgage Bonds”). The Substituted Mortgage Bonds may only be delivered to the Trustee upon receipt by the Trustee of (i) a letter from Moody’s (as hereinafter defined), dated within ten days prior to the date of delivery of the Substituted Mortgage Bonds, stating that its rating of the Substituted Mortgage Bonds is at least equal to its then current rating on the Bonds of the 2033 Series , (ii) a letter from S&P (as hereinafter defined), dated within ten days prior to the date of delivery of the Substituted Mortgage Bonds, stating that its rating to the Substituted Mortgage Bonds is at least equal to its then current rating on the Bonds of the 2033 Series, (iii) an opinion of counsel which may be counsel to the Company or any successor entity, to the effect that the Substituted Mortgage Bonds shall have been duly and validly authorized, executed, authenticated, and delivered and shall constitute the valid, legally binding and enforceable obligations of the Company or any successor entity enforceable in accordance with their terms, except as limited by bankruptcy, insolvency or other laws affecting the enforcement of mortgagees’ and other creditors’ rights and shall be entitled to the benefit of the mortgage and deed of trust or other similar instrument pursuant to which they shall have been issued, (iv) an opinion of Bond Counsel, as defined in the Revenue Bond Indenture, to the effect that the substitution of the Substituted Mortgage Bonds will not adversely affect the exemption from federal income taxes of interest on the Revenue Bonds and (v) such other certificates and documents with respect to the issuance and delivery of the Substituted Mortgage Bonds as may be required by law or as the Trustee may reasonably request.

“Moody’s” means Moody’s Investor Services, Inc., a corporation organized and existing under the laws of the State of Delaware, its successors and their assigns, except that if such corporation shall be dissolved or liquidated or shall no longer perform the functions of a securities rating agency, then the term “Moody’s” shall be deemed to refer to any other nationally recognized securities rating agency selected by the Company.

“S&P” means Standard & Poor’s Ratings Services, a division of The McGraw Hill Companies, Inc., duly organized and existing under and by virtue of the laws of the State of New York, and its successors and assigns, except that if such rating agency shall be dissolved or liquidated or shall no longer perform the functions of a securities rating agency, then the term “S&P” shall be deemed to refer to any other nationally recognized securities rating agency selected by the Company.

SECTION 7. Bonds of the 2033 Series shall not be subject to redemption prior to maturity, except as provided in this Article III.

ARTICLE IV

ADDITIONAL COVENANTS

The Company hereby covenants, warrants and agrees:

SECTION 1. That the Company is lawfully seized and possessed of all of the mortgaged property described in the granting clauses of this Supplemental Indenture; that it has good, right and lawful authority to mortgage the same as provided in this Supplemental Indenture; and that such mortgaged property is, at the actual date of the initial issue of the Bonds of the 2033 Series, free and clear of any deed of trust, mortgage, lien, charge or encumbrance thereon or affecting the title

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thereto prior to the Indenture, except as set forth in the granting clauses of the Original Indenture, the Twenty-Eighth Supplemental Indenture, the Thirtieth Supplemental Indenture, the Thirty-First Supplemental Indenture, the Thirty-Second Supplemental Indenture or the Thirty-fifth Supplemental Indenture or this Supplemental Indenture.

SECTION 2. So long as any Bonds of any series originally issued prior to January 1, 1997 are outstanding, in the event all or substantially all of the electric properties shall have been released as an entirety from the lien of the Original Indenture, the Company will, at any time or from time to time within six months after the date of such release, retire Bonds outstanding under the Original Indenture in an aggregate principal amount equal to the fair value of the electric properties so released pursuant to Section 3 of Article VII of the Original Indenture, as stated in the engineer’s certificate required by Section 3(b) of said Article VII, and the proceeds of the electric properties so released pursuant to Section 5 of said Article VII. Such retirement of Bonds shall be effected in either one or both of the following methods:

(a) By the withdrawal pursuant to Section 2 of Article VIII of the Original Indenture of any moneys deposited with the Trustee pursuant to Sections 3(d), 4(d) and 5 of Article VII of the Original Indenture upon such release; or

(b) By causing the Trustee to purchase or redeem bonds, pursuant to Section 8 of Article VIII of the Original Indenture, out of any moneys deposited with the Trustee pursuant to Sections 3(d), 4(d) and 5 of Article VII of the Original Indenture upon such release.

The Bonds to be so retired pursuant to this Section 3 shall include a principal amount of Bonds of each Series then outstanding in the same ratio to the aggregate principal amount of all Bonds so retired as the aggregate principal amount of all Bonds of each Series outstanding immediately prior to such release bears to the total principal amount of all Bonds then outstanding.

ARTICLE V

AMENDMENTS AND RESERVATION OF RIGHTS TO AMEND THE ORIGINAL INDENTURE

SECTION 1. So long as any of the Bonds of any series originally issued prior to January 1, 1997 shall remain outstanding:

(a) Notwithstanding the provisions of Section 4 of Article III of the Original Indenture, no Bonds shall be authenticated and delivered pursuant to the provisions of Article III of the Original Indenture and issued upon the basis of net bondable value of property additions for an aggregate principal amount in excess of sixty percent (60%) of the net bondable value of property additions not subject to an unfunded prior lien.

For the purposes of Subsections (e) and (f) of the definition of “net bondable value of property additions not subject to an unfunded prior lien,” contained in Article I of the Original Indenture, and Subdivisions 8 and 9 of clause (a) of Section 4 of Article III of the Original

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Indenture, in all computations made with respect to a period subsequent to April 1, 1949, the deductions therein referred to shall in each case be ten-sixths (10/6ths) of the respective amounts mentioned, in lieu of ten-sevenths (10/7ths).

(b) Notwithstanding the provisions of Section 3(a) of Article VIII of the Original Indenture, no moneys received by the Trustee pursuant to Section 5(a) of Article III of the Original Indenture shall be paid over by the Trustee in an amount in excess of sixty percent (60%) of the net bondable value of property additions not subject to an unfunded prior lien, and for the purposes of Section 3 of Article VII of the Original Indenture, the amount of cash required to be deposited by the Company pursuant to Subsection (d) of said Section 3 of Article VII shall not be reduced in an amount in excess of sixty percent (60%) of the net bondable value of property additions not subject to an unfunded prior lien.

(c) For the purposes of clauses (c) and (d) of the definition of “net bondable value of property additions subject to an unfunded prior lien,” contained in Article I of the Original Indenture, and Subsection 7 of clause (a) of Section 4 of Article III of the Original Indenture, in all computations made with respect to a period subsequent to April 1, 1949, the deductions therein referred to shall in each case be ten-sixths (10/6ths) of the respective amounts mentioned, in lieu of ten-sevenths (10/7ths).

(d) Subsection (a) of Section 14, clauses (1) and (2) of Subsection (a) of Section 16 of Article IV and clause (1) of Subsection (b) of Section 1 of Article XII of the Original Indenture shall be deemed amended by substituting the words “sixty percent (60%)” for “seventy percent (70%)” where they appear in said provisions of the Original Indenture.

(e) The definition of the term “net earnings available for interest, depreciation and property retirement,” as contained in Article I of the Original Indenture, shall be deemed to mean the net earnings of the Company ascertained as follows:

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the Original Indenture, the proceeds of which shall have exceeded Five Hundred Thousand Dollars ($500,000), within or after the particular period for which the calculation of net earnings of the Company available for interest, depreciation and property retirement is made, then, in computing the net earnings of the Company available for interest, depreciation and property retirement, the net earnings or net losses of such property for the whole of such period shall be excluded to the extent practicable on the basis of actual earnings and expenses of such property or on the basis of such estimates of the earnings and expenses of such property as the signers of an officers’ certificate filed with the Trustee pursuant to Section 3(b) of Article III or Section 16 of Article IV of the Original Indenture shall deem proper.

(f) Notwithstanding the provisions of clauses (1) and (2) of subsection (b) of Article III, and Subsection (b) of Section 14 of Article IV, and Subsection (b) of Section 16 of Article IV and clause (2) of Subsection (b) of Section 1 of Article XII of the Original Indenture, the computation of net earnings required therein shall be made as provided in Subsection (e) of this Section 1, and the net earnings tests required in said mentioned provisions of Articles III, IV and XII of the Original Indenture shall be based on two times the annual interest charges described in such provisions, instead of two and one-half times such charges, but shall not otherwise affect such provisions or relieve from the requirements therein pertaining to ten percent (10%) of the principal amount of Bonds therein described.

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SECTION 2. All of the Bonds of the 2033 Series and of any series initially issued after the initial issuance of Bonds of the 2033 Series shall, from time to time, be executed on behalf of the Company by its Chairman of the Board, Chief Executive Officer, President or one of its Vice Presidents whose signature, notwithstanding the provisions of Section 12 of Article II of the Original Indenture, may be by facsimile, and its corporate seal (which may be in facsimile) shall be thereunto affixed and attested by its Secretary or one of its Assistant Secretaries whose signature, notwithstanding the provisions of the aforesaid Section 12, may be by facsimile.

In case any of the officers who have signed or sealed any of the Bonds of the 2033 Series or of any series initially issued after the initial issuance of Bonds of the 2033 Series manually or by facsimile shall cease to be such officers of the Company before such Bonds so signed and sealed shall have been actually authenticated by the Trustee or delivered by the Company, such Bonds nevertheless may be authenticated, issued and delivered with the same force and effect as though the person or persons who so signed or sealed such Bonds had not ceased to be such officer or officers of the Company; and also any such Bonds may be signed or sealed by manual or facsimile signature on behalf of the Company by such persons as at the actual date of the execution of any of such Bonds shall be the proper officers of the Company, although at the nominal date of any such Bond any such person shall not have been such officer of the Company.

SECTION 3. The Company reserves the right subject to appropriate corporate action, but without the consent or other action of holders of bonds of any series created after January 1, 1997, to make such amendments to the Original Indenture, as supplemented, as shall be necessary in order to amend Article VII thereof by adding thereto a Section 8 and a Section 9 to read as follows:

“SECTION 8. Notwithstanding any other provision of this Indenture, unless an event of default shall have happened and be continuing, or shall happen as a result of the making or granting of an application to release mortgaged property permitted by this Section 8, the Trustee shall release from the lien of this Indenture any mortgaged property if the fair value to the Company of all of the property constituting the trust estate (excluding the mortgaged property to be released but including any mortgaged property to be acquired by the Company with the proceeds of, or otherwise in connection with, such release) equals or exceeds an amount equal to 10/7ths of the aggregate principal amount of outstanding Bonds and prior lien bonds outstanding at the time of such release, upon receipt by the Trustee of:

“(a) an officers’ certificate dated the date of such release, requesting such release, describing in reasonable detail the mortgaged property to be released and stating the reason for such release;

“(b) an engineer’s certificate, dated the date of such release, stating (i) that the signer of such engineer’s certificate has examined such officers’ certificate in connection with such release, (ii) the fair value to the

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Company, in the opinion of the signer of such engineer’s certificate, of (A) all of the property constituting the trust estate, and (B) the mortgaged property to be released, in each case as of a date not more than 90 days prior to the date of such release, and (iii) that in the opinion of such signer, such release will not impair the security under this Indenture in contravention of the provisions hereof;

“(c) in case any bondable property is being acquired by the Company with the proceeds of, or otherwise in connection with, such release, an engineer’s certificate, dated the date of such release, as to the fair value to the Company, as of the date not more than 90 days prior to the date of such release, of the bondable property being so acquired (and if within six months prior to the date of acquisition by the Company of the bondable property being so acquired, such bondable property has been used or operated by a person or persons other than the Company in a business similar to that in which it has been or is to be used or operated by the Company, and the fair value to the Company of such bondable property, as set forth in such certificate, is not less than $25,000 and not less than 1% of the aggregate principal amount of Bonds at the time outstanding, such certificate shall be an independent appraiser’s certificate);

“(d) an officer’s certificate, dated the date of such release, stating the aggregate principal amount of outstanding Bonds and prior lien bonds outstanding at the time of such release, and stating that the fair value to the Company of all of the property constituting the trust estate (excluding the mortgaged property to be released but including any bondable property to be acquired by the Company with the proceeds of, or otherwise in connection with, such release) stated on the independent appraiser’s certificate filed pursuant to Section 8(c) equals or exceeds an amount equal to 10/7ths of such aggregate principal amount;

“(e) an officers’ certificate, dated the date of such release, stating that, the Company is not, and by the making or granting of the application will not be, in default in the performance of any of the terms and covenants of this Indenture;

“(f) an opinion of counsel, dated the date of such release, as to compliance with conditions precedent.

“SECTION 9. If the Company is unable to obtain, in accordance with any other Section of this Article VII, the release from the lien of this Indenture of any property constituting part of the trust estate, unless an event of default shall have happened and be continuing, or shall happen as a result of the making or granting of an application to release mortgaged property permitted by this Section 9, the Trustee

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shall release from the lien of this Indenture any mortgaged property if the fair value to the Company thereof, as shown by the engineer’s certificate filed pursuant to Section 9(b), is less than 1/2 of 1% of the aggregate principal amount of outstanding Bonds and prior lien bonds outstanding at the time of such release, provided that the aggregate fair value to the Company of all mortgaged property released pursuant to this Section 9, as shown by all engineer’s certificates filed pursuant to Section 9(b) in any period of 12 consecutive calendar months which includes the date of such engineer’s certificate, shall not exceed 1% of the aggregate principal amount of the outstanding Bonds and prior lien bonds outstanding at the time of such release, upon receipt by the Trustee of:

“(a) an officers’ certificate, dated the date of such release, requesting such release, describing in reasonable detail the mortgaged property to be released and stating the reason for such release;

“(b) an engineer’s certificate, dated the date of such release, stating (A) that the signer of such engineer’s certificate has examined such officers’ certificate in connection with such release, (B) the fair value to the Company, in the opinion of the signer of such engineer’s certificate, of such mortgaged property to be released as of a date not more than 90 days prior to the date of such release, and (C) that in the opinion of such signer such release will not impair the security under this Indenture in contravention of the provisions hereof;

“(c) an officers’ certificate, dated the date of such release, stating the aggregate principal amount of outstanding Bonds and prior lien bonds outstanding at the time of such release, that 1/2 of 1% of such aggregate principal amount does not exceed the fair value to the Company of the mortgaged property for which such release is applied for as shown by the engineer’s certificate referred to in Section 9(b), and that 1% of such aggregate principal amount does not exceed the aggregate fair value to the Company of all mortgaged property released from the lien of this Indenture pursuant to this Section 9 as shown by all engineer’s certificates filed pursuant to Section 9(b) in such period of 12 consecutive calendar months;

“(d) an officers’ certificate, dated the date of such release, stating that, the Company is not, and by the making or granting of the application will not be, in default in the performance of any of the terms and covenants of this Indenture; and

“(e) an opinion of counsel, dated the date of such release, as to compliance with conditions precedent.”

The Company also reserves the right subject to appropriate corporate action, but without the consent or other action of holders of Bonds of any series created after January 1, 1997 to amend, modify or delete any other provision of the Original Indenture, as supplemented, as may be necessary in order to effectuate the intents and purposes contemplated by the foregoing Sections 8 and 9.

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SECTION 4. The Company reserves the right subject to appropriate corporate action, but without the consent or other action of holders of Bonds of any series created after January 1, 1997 to:

(a) delete as a condition to the authentication of additional Bonds pursuant to Sections 4, 5 or 6 of Article III of the Original Indenture the requirement to file or deposit with the Trustee the officers’ certificate described in Section 3(b) of Article III of the Original Indenture;

(b) delete as a condition to the consolidation or merger of the Company into, or sale by the Company of its property as an entirety or substantially as an entirety to another corporation the requirement set forth in Section 1(b)(2) of Article XII of the Original Indenture;

(c) delete as a condition to the release of property pursuant to Section 3 of Article VII of the Original Indenture, the requirement to obtain an independent engineer’s certificate under the circumstances set forth in Section 3(c) of Article VII; and

(d) amend, modify or delete any other provision of the Original Indenture, as supplemented, as may be necessary in order to effectuate the intents and purposes contemplated by this Section 4.

SECTION 5. The Company reserves the right, subject to appropriate action, but without any consent or other action by holders of Bonds of the 2033 Series, or of any subsequent series of bonds, to clarify the ability of the Company to issue variable rate bonds under the Original Indenture, notwithstanding any provision of the Original Indenture to the contrary. The Company may make such other amendments to the Original Indenture as may be necessary or desirable in the opinion of the Company to effect the foregoing;”

SECTION 6. The Company reserves the right, subject to appropriate action, but without any consent or other action by holders of Bonds of the 2033 Series, or of any subsequent series of bonds, to amend the Original Indenture as may be necessary in order to permit the Company to deliver to the Trustee in substitution for any bonds issued under the Original Indenture, mortgage bonds or other similar instruments of the Company or any successor entity, whether by merger, combination or acquisition of all or substantially all of the assets of the Company, or otherwise, issued under a mortgage and deed of trust or similar instrument of the Company or any successor entity in like principal amount of like term and bearing the same rate of interest as the original bonds (such substituted bonds hereinafter being referred to as the “Substituted Mortgage Bonds”). The Substituted Mortgage Bonds may only be delivered to the Trustee upon receipt by the Trustee of (i) if the original bonds were rated by Moody’s, a letter from Moody’s (as hereinafter defined), dated within ten days prior to the date of delivery of the Substituted Mortgage Bonds, stating that its rating of the

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Substituted Mortgage Bonds is at least equal to its then current rating on the original bonds, (ii) if the original bonds were rated by S&P, a letter from S&P (as hereinafter defined), dated within ten days prior to the date of delivery of the Substituted Mortgage Bonds, stating that its rating to the Substituted Mortgage Bonds is at least equal to its then current rating on the original bonds, (iii) an opinion of counsel which may be counsel to the Company or any successor entity, to the effect that the Substituted Mortgage Bonds shall have been duly and validly authorized, executed, authenticated, and delivered and shall constitute the valid, legally binding and enforceable obligations of the Company or any successor entity enforceable in accordance with their terms, except as limited by bankruptcy, insolvency or other laws affecting the enforcement of mortgagees’ and other creditors’ rights and shall be entitled to the benefit of the mortgage and deed of trust or other similar instrument pursuant to which they shall have been issued and (iv) such other certificates and documents with respect to the issuance and delivery of the Substituted Mortgage Bonds as may be required by law or as the Trustee may reasonably request. The Company may make such other amendments to the Original Indenture as may be necessary or desirable in the opinion of the Company to effect the foregoing.

“Moody’s” means Moody’s Investor Services, Inc., a corporation organized and existing under the laws of the State of Delaware, its successors and their assigns, except that if such corporation shall be dissolved or liquidated or shall no longer perform the functions of a securities rating agency, then the term “Moody’s” shall be deemed to refer to any other nationally recognized securities rating agency selected by the Company.

“S&P” means Standard & Poor’s Ratings Services, a division of The McGraw Hill Companies, Inc., duly organized and existing under and by virtue of the laws of the State of New York, and its successors and assigns, except that if such rating agency shall be dissolved or liquidated or shall no longer perform the functions of a securities rating agency, then the term “S&P” shall be deemed to refer to any other nationally recognized securities rating agency selected by the Company.

SECTION 7. The Company reserves the right, subject to appropriate action, but without any consent or other action by holders of Bonds of the 2033 Series, or of any subsequent series of bonds, to amend the Original Indenture to add the following new section:

“This Indenture shall be deemed to be a contract made under the laws of the State of Kansas and for all purposes shall be construed in accordance with the laws of the State of Kansas, without regard to conflicts of laws principles thereof.”

SECTION 8. The Company reserves the right, subject to appropriate action, but without any consent or other action by holders of Bonds of the 2033 Series, or of any subsequent series of bonds, to amend the Original Indenture to delete Article IX, Section 1(j). The Company may make such other amendments to the Original Indenture as may be necessary or desirable in the opinion of the Company to effect the foregoing.

SECTION 9. The Company reserves the right, subject to appropriate action, but without any consent or other action by holders of Bonds of the 2033 Series, or of any subsequent series of bonds, to amend the Original Indenture to delete Article IV, Section 14(b) and reserves the

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right to further amend, modify or delete any other provision of the Original Indenture, as supplemented, as may be necessary in order to effectuate the intents and purposes contemplated by this Section 9.

SECTION 10. The Company reserves the right, subject to appropriate action, but without any consent or other action by holders of Bonds of the 2033 Series, or of any subsequent series of bonds, to amend the Original Indenture to (i) add Nuclear Fuel to the definition of “Property Additions”; provided that there shall be no restrictions under the Original Indenture on the application of any controls, liens, regulations, easements, restrictions, exceptions or reservations by any governmental authority on the Nuclear Fuel (ii) to allow the Company to at any time, unless the Company is in default in the payment of the interest on any of the bonds then outstanding or there is an ongoing event of default without any release or consent by, or report to, the Trustee, sell or otherwise dispose of, free from the lien of the Original Indenture, any Nuclear Fuel which shall have become old, inadequate, obsolete, worn out, unfit, unadapted, unserviceable, undesirable or unnecessary for use in the operations of the Company upon the replacement or substitution of such Nuclear Fuel with other Nuclear Fuel of at least equal value and subject to the lien of the Original Indenture and (iii) to further amend, modify or delete any other provision of the Original Indenture, as supplemented, as may be necessary in order to effectuate the intents and purposes contemplated by this Section 10.

The term ‘Nuclear Fuel’ shall mean (a) any fuel element, including nuclear fuel and associated means (and any similar or analogous device or substance), whether or not classified as fuel and whether or not chargeable to operating expenses, comprising or intended to comprise, or formerly comprising, the core, or other part, of a nuclear reactor or any similar or analogous device, (b) any fuel element, including nuclear fuel, and associated means (and any similar or analogous device or substance) while in the process of fabrication or preparation and special nuclear or other materials held for use in such fabrication or preparation, (c) any substances or materials formerly comprising such nuclear fuel and associated means (or any similar or analogous device or substance) and which substances or materials are undergoing or have undergone reprocessing and (d) uranium, thorium, plutonium, and any other substance or material from time to time used or selected for use by the Company as fuel material, or as potential fuel material, in a nuclear reactor or any similar or analogous device.”

SECTION 11. The Company reserves the right, subject to appropriate action, but without any consent or other action by holders of Bonds of the 2033 Series, or of any subsequent series of bonds, to amend the Original Indenture to:

(I) Eliminate maintenance and improvement fund requirements;

(II) Simplify the provisions for release of obsolete property, de minimis property releases and substitution of property and unfunded property;

(III) Permit additional terms of bonds or forms of bond in supplemental indentures, including terms for uncertificated and global securities and medium-term notes;

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(IV) Make any changes necessary to conform the Mortgage with the requirements of the Trust Indenture Act;

(V) Add defeasance provisions providing for covenant and legal defeasance options;

(VI) Permitting the Company to remove the trustee in certain circumstances;

(VII) Providing for direction to the trustee under the Mortgage to vote pledged prior lien bonds for specified amendments to the prior lien mortgage;

(VIII) Providing broader investment directions to the trustee or permitting the Company to direct investment of money held by the trustee, so long as there is no event of default under the Mortgage;

(IX) Amending the definition of “Excepted Property” to exclude property which generally cannot be mortgaged without undue administrative burden (i.e. automobiles), but allowing the Company to subject Excepted Property to the Mortgage;

(X) Amending the definition of “Bondable Property” to allow all mortgaged property to be bondable; and

(XI) Updating the definition of “Permitted Liens.”

ARTICLE VI

MISCELLANEOUS PROVISIONS

SECTION 1. The Trustee accepts the trusts herein declared, provided, created or supplemented and agrees to perform the same upon the terms and conditions herein and in the Original Indenture, as amended, set forth and upon the following terms and conditions.

SECTION 2. The Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this Supplemental Indenture or for or in respect of the recitals contained herein, all of which recitals are made by the Company solely. In general each and every term and condition contained in Article XIII of the Original Indenture, as amended by the Second Supplemental Indenture, shall apply to and form part of this Supplemental Indenture with the same force and effect as if the same were herein set forth in full with such omissions, variations and insertions, if any, as may be appropriate to make the same conform to the provisions of this Supplemental Indenture.

SECTION 3. Whenever in this Supplemental Indenture either of the parties hereto is named or referred to, such reference shall, subject to the provisions of Articles XII and XIII of the Original Indenture, be deemed to include the successors and assigns of such party, and all the covenants

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and agreements in this Supplemental Indenture contained by or on behalf of the Company, or by or on behalf of the Trustee, shall, subject as aforesaid, bind and inure to the respective benefits of the respective successors and assigns of such parties, whether so expressed or not.

SECTION 4. Nothing in this Supplemental Indenture, expressed or implied, is intended or shall be construed, to confer upon, or to give to, any person, firm or corporation, other than the parties hereto and the holders of the Bonds and coupons outstanding under the Indenture, any right, remedy or claim under or by reason of this Supplemental Indenture or any covenant, condition, stipulation, promise or agreement hereof, and all the covenants, conditions, stipulations, promises and agreements in this Supplemental Indenture contained by and on behalf of the Company shall be for the sole and exclusive benefit of the parties hereto, and of the holders of the Bonds and of the coupons outstanding under the Indenture.

SECTION 5. This Supplemental Indenture may be executed in several counterparts, and all such counterparts executed and delivered, each as an original, shall constitute but one and the same instrument.

SECTION 6. The Titles of the several Articles of this Supplemental Indenture shall not be deemed to be any part thereof.

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IN WITNESS HEREOF, WESTAR ENERGY, INC., party hereto of the first part, has caused its corporate name to be hereunto affixed, and this instrument to be signed and sealed by its Chairman of the Board, President, Chief Executive Officer or a Vice President, and its corporate seal to be attested by its Secretary or an Assistant Secretary for and in its behalf, and BNY MIDWEST TRUST COMPANY, party hereto of the second part, has caused its corporate name to be hereunto affixed, and this instrument to be signed and sealed by its duly authorized officer and its corporate seal to be attested by its duly authorized officer, all as of the day and year first above written.

S-1

STATE OF KANSAS         )

                                                : ss.:

COUNTY OF SHAWNEE  )

BE IT REMEMBERED, that on this 1st day of June 2004, before me, the undersigned, a Notary Public within and for the County and State aforesaid, personally came Mark A. Ruelle and Larry D. Irick, of Westar Energy, Inc., a corporation duly organized, incorporated and existing under the laws of the State of Kansas, who are personally known to me to be such officers, and who are personally known to me to be the same persons who executed as such officers the within instrument of writing, and such persons duly acknowledged the execution of the same to be the act and deed of said corporation.

IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my official seal on the day and year last above written.

S-2

STATE OF ILLINOIS )

                                      : ss.:

COUNTY OF COOK  )

BE IT REMEMBERED, that on this 1st day of June 2004, before me, the undersigned, a Notary Public within and for the County and State aforesaid, personally came J. Bartolini and D.G. Donovan, of BNY Midwest Trust Company, an Illinois trust company, who are personally known to me to be such officers, and who are personally known to me to be the same persons who executed as such officers the within instrument of writing, and such persons duly acknowledged the execution of the same to be the act and deed of said corporation.

S-3

STATE OF KANSAS         )

                                               : ss.:

COUNTY OF SHAWNEE  )

BE IT REMEMBERED, that on this 1st day of June 2004, before me, the undersigned, a Notary Public within and for the County and State aforesaid, personally came Mark A. Ruelle and Larry D. Irick, of Westar Energy, Inc., a corporation duly organized, incorporated and existing under the laws of the State of Kansas, who are personally known to me to be such officers, being by me respectively duly sworn, did each say that the said Mark A. Ruelle is Executive Vice President and Chief Financial Officer and that the said Larry D. Irick is Vice President, General Counsel and Corporate Secretary of said corporation, that the consideration of and for the foregoing instrument was actual and adequate, that the same was made and given in good faith, for the uses and purposes therein set forth and without any intent to hinder, delay, or defraud creditors or purchasers.

IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my official seal on the day and year last above written.

S-4

APPENDIX A

to

THIRTY-SIXTH SUPPLEMENTAL INDENTURE

Dated as of June 1, 2004

Westar Energy, Inc.

to

BNY Midwest Trust Company

(as successor to

Harris Trust and Savings Bank)

DESCRIPTION OF PROPERTIES

LOCATED IN THE STATE OF KANSAS

FIRST

PARCELS OF REAL ESTATE

Barton County

Great Bend Radio Tower

A tract of real estate situate in the Southeast Quarter (SE/4) of Section Sixteen (16), Township Nineteen (19) South, Range Thirteen (13) West, Barton County, Kansas, by metes and bounds described as follows, to-wit: Commencing at a point 729.05 feet East of the Northwest corner (NWc) of said SE/4 for a point of beginning; thence East a distance of 600 feet on and along the North line of said SE/4 to the East line of the W/2 of said Quarter; thence South 470.44 feet; thence West 600 feet parallel with the North line of said SE/4; thence North 470.44 feet to the point of beginning, subject, however, to all covenants, easements, restrictions and reservations now of record and subject to all taxes and assessments, general and special, not now due and payable.

Greenwood County

Eureka Radio Tower

A tract of land in the Southeast Quarter of the Southwest Quarter (SE ¼ SW ¼) OF section Thirty (30), Township Twentyfour (24) South, Range Eleven (11) East of the Sixth (6 ^th ) Principal Meridian, Greenwood County, Kansas, more particularly described as follows, to-wit: Beginning on the South line of the Southwest Quarter (SW ¼) of said Section Thirty (30) at a point located 1,450 feet East of the Southwest Corner (SW/c) of said Section Thirty (30); thence North parallel with the West line of said Southwest Quarter (SW ¼), a distance of 550 feet; thence East parallel with said South line, a distance of 550 feet; thence South to a point on said South line located 550 feet West of the point of beginning; thence West to the point of beginning.

Jackson County

Denison Substation

A tract of land located in the Southwest Quarter of Section 27, Township 7 South, Range 15 East of the 6 ^th P.M., Jackson County, Kansas, said tract more particularly described as follows: Beginning on the South line of said Southwest Quarter at a point 205 feet East of the Southwest corner of said Southwest Quarter; thence North 01°38'40" West a distance of 100 feet; thence North 88°21'20" East 80 feet; thence South 01°38'40" East a distance of 100 feet to said South line; thence West along said South line to the point of beginning.

Johnson County

Bonita Substation

The North 660 feet of the West 660 feet of the South Half of the Northeast Quarter of Section 25, Township 14 South, Range 23 East, Johnson County, Kansas.

A-2

Shawnee Operations Center

Lot 18, PERIMETER PARK, NINTH PLAT, a subdivision in the City of Shawnee, Johnson County, Kansas, according to the recorded plat thereof, EXCEPT that part thereof described as follows:

Beginning at the Northwest corner of said Lot 18; thence North 89°45'40" East, along the North line of said Lot 18, a distance of 647.81 feet to a corner of said Lot 18, said corner being on the Southerly right-of-way line of 86 ^th Street, as now established; thence Southeasterly along said southerly right-of-way line, and along a curve to the left, having a radius of 530.00 feet, a central angle of 10°02'56" and whose initial tangent bearing is South 51°07'38" East, a distance of 92.95 feet; thence South 28°49'27" West, departing said right-of-way line, a distance of 137.05 feet; thence South 89°45'40" West, a distance of 659.50 feet, to a point on the West line of said Lot 18; thence North 00°13'22" East, along said West line, a distance of 171.83 feet to the Northwest corner of said Lot 18 and the point of beginning, containing 2.7210 acres, more or less.

Lot 19, PERIMETER PARK, NINTH PLAT, a subdivision in the City of Shawnee, Johnson County, Kansas, according to the recorded plat thereof, EXCEPT that part thereof described as follows:

Beginning at the Southwest corner of said Lot 19; thence North 00°13'22" East, along the West line of said Lot 19, a distance of 129.17 feet; thence North 89°45'40" East, departing said West line, a distance of 532.40 feet to a point on the Westerly right-of-way line of Cole Parkway, as now established; thence Southeasterly along said Westerly right-of-way line, and along a curve to the left having a radius of 530.00 feet, a central angel of 18°44'03" and whose initial tangent bearing is South 32°23'35" East, a distance of 173.30 feet to the Southeast corner of said Lot 19; thence South 89°45'40" West, along the South line of said Lot 19, a distance of 647.81 feet to the point of beginning, containing 1.7311 acres, more or less.

Shawnee County

Sherwood Substation

Lots 4 thru 18, inclusive, Block F, Sherwood Estates Subdivision No. 59, Shawnee County, Kansas.

A-3

I, Larry D. Irick, Vice President, General Counsel and Corporate Secretary, Westar Energy, Inc., formerly known as The Kansas Power and Light Company, in Topeka, Kansas, being duly sworn, depose and say:

That a Thirtieth Supplemental Indenture dated February 1, 1993, was granted by Westar Energy, Inc. to Harris Trust and Savings Bank, Chicago, Illinois, with respect to bonds in the aggregate amount of $58,500,000, and that such Thirtieth Supplemental Indenture was recorded with the Register of Deeds of Shawnee County, Kansas, on February 3, 1993, in Book 2780 at Page 626 and filed in the Office of the Kansas Secretary of State on February 3, 1993, as File Number 1876325.

That a Thirty-Sixth Supplemental Indenture dated as of June 1, 2004, was granted by Westar Energy, Inc. to BNY Midwest Trust Company (successor to Harris Trust and Savings Bank), Chicago, Illinois, with respect to bonds in the amount of $58,340,000.

That all of the $58,340,000 consideration stated in the Thirty-Sixth Supplemental Indenture was included as principal indebtedness under the Thirtieth Supplemental Indenture. The Thirtieth Supplemental Indenture is recorded in the Office of the Shawnee County Register of Deeds, as recited above. Therefore, under the provisions of K.S.A. 79-3102(d)(3), no mortgage registration fee is required in connection with the recording of the Thirty-Sixth Supplemental Indenture.

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Further affiant saith not.

Signed this 10th day of June, 2004.

Subscribed and sworn to before me this 10th day of June, 2004.

My Appointment Expires:

11/18/04

Thirty-Sixth Supplemental Indenture recorded in Book 4044, Page 066, Shawnee County Register of Deeds.

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Exhibit 4.2

WESTAR ENERGY, INC.

TO

BNY MIDWEST TRUST COMPANY

as Trustee

(as Successor to

HARRIS TRUST AND SAVINGS BANK)

THIRTY-SEVENTH SUPPLEMENTAL INDENTURE

Dated as of June 17, 2004

First Mortgage Bonds, 6.00% Series Due 2014

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TABLE OF CONTENTS ^a

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APPENDIX A

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THIRTY-SEVENTH SUPPLEMENTAL INDENTURE, dated as of the 17th day of June, Two Thousand and Four, made by and between Westar Energy, Inc., formerly The Kansas Power and Light Company, a corporation organized and existing under the laws of the State of Kansas (hereinafter called the “ Company ”), party of the first part, and BNY Midwest Trust Company, an Illinois trust company whose mailing address is 2 North LaSalle Street, Suite 1020, Chicago, IL 60602 (hereinafter called the “ Trustee ”), as Trustee (as successor to Harris Trust and Savings Bank), under the Mortgage and Deed of Trust dated July 1, 1939, hereinafter mentioned, party of the second part;

WHEREAS, the Company has heretofore executed and delivered to the Trustee its Mortgage and Deed of Trust dated July 1, 1939 (hereinafter referred to as the “ Original Indenture ”), to provide for and to secure the issue of First Mortgage Bonds of the Company, issuable in series, and to declare the terms and conditions upon which the Bonds (as defined in the Original Indenture) are to be issued thereunder; and

WHEREAS, the Company has heretofore executed and delivered to the Trustee Thirty-Six Supplemental Indentures supplemental to said Original Indenture, of which Thirty-Four provided for the issuance thereunder of series of the Company’s First Mortgage Bonds, and there is set forth below information with respect to such Supplemental Indentures as have provided for the issuance of Bonds, and the principal amount of Bonds which remain outstanding as of June 17, 2004.

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