Subject to Completion, dated             , 2009

Prospectus

                           shares

Generac Holdings Inc.

Common stock

This is an initial public offering of shares of common stock by Generac Holdings Inc. Generac is selling                   shares of common stock. The estimated initial public offering price is between $                  and $                  per share.

After pricing the offering, we expect that the shares will be listed on the New York Stock Exchange under the symbol "GNRC."

Investing in our common stock involves a high degree of risk. See "Risk factors" beginning on page 16.

The underwriters may also purchase up to an additional                  shares from us at the public offering price, less the underwriting discount, within 30 days from the date of this prospectus.

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

The shares will be ready for delivery on or about                  , 2009.

                           , 2009

Table of contents

You should rely only on the information contained in this prospectus. We have not, and the underwriters have not, authorized any other person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. We are not, and the underwriters are not, making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus is only accurate as of the date on the front cover of this prospectus. Our business, financial condition, results of operations and prospects may have changed since that date.

i

Table of Contents

Prospectus summary

This section summarizes key information contained elsewhere in this prospectus and is qualified in its entirety by the more detailed information and consolidated financial statements included elsewhere in this prospectus. You should carefully review the entire prospectus, including the risk factors, the consolidated financial statements and the notes thereto, and the other documents to which this prospectus refers before making an investment decision. Unless the context requires otherwise, references in this prospectus to "Generac," "we," "us," "our company" or similar terms refer to Generac Holdings Inc. and its subsidiaries.

Our company

We are a leading designer and manufacturer of a wide range of automatic, stationary standby and portable generators. We have a leading market share of the standby generator market in the United States and Canada, having grown our company organically by a 16% compound annual growth rate, or CAGR, since 2000. We design, engineer and manufacture generators with an output of between 800W and 9mW of power for which we also manufacture, source and modify engines, alternators, automatic transfer switches and other necessary components. Our generators are fueled by natural gas, liquid propane, gasoline, diesel and Bi-Fuel™ (combined diesel and natural gas) and serve the power requirements of a wide variety of end markets, including the residential, commercial, industrial and telecommunications markets. For the twelve months ended September 30, 2009, we generated net sales of $606.9 million, a net loss of $491.4 million (includes a non-cash goodwill and trade name impairment charge of $583.5 million) and Adjusted EBITDA (as defined on page 13) of $153.7 million. For an explanation of Adjusted EBITDA and a reconciliation of Adjusted EBITDA to net income, see pages 14 and 15.

While standby power systems have long been present in hospitals, data centers and industrial facilities, their use for residential and small business applications is a relatively recent development. Our leadership position, first mover advantage and focus on natural gas generators have enabled us to successfully penetrate these new markets. We believe that our leading market position is largely attributable to our strategy of providing high-quality, innovative and affordable products through our extensive and multi-layered distribution network. Our products are available in over 17,000 outlets across the United States and Canada, and are distributed through independent and industrial dealers, electrical wholesalers, national accounts, private label arrangements, retailers, catalogs and e-commerce merchants.

Because of our sourcing model, product engineering and efficient manufacturing operations, we generate attractive gross margins while competitively pricing our products. Our business generates strong cash flow, enhanced by favorable tax attributes and low capital expenditure requirements.

Our market opportunity

For the reasons we describe below, we believe that our market will provide continued organic growth opportunities that we can exploit given our focus on product awareness, affordability and customer reach. See "Industry" for a more detailed discussion of our market opportunity and "Risk Factors" for a detailed discussion of factors that may have an impact on our ability to realize this opportunity.

1

Table of Contents

Aging U.S. power grid leading to recurring power outages

Disruptions to the aging U.S. power grid are increasing due to demand growth, equipment failures, prevalent under-investment and a variety of environmental causes. Given the large estimated cost to upgrade the U.S. power grid, we believe it is unlikely that the core causes of power disturbances will be addressed in the near future. Continued outages increase consumers' awareness of the advantages of generators as reliable sources of back-up electrical power.

Generators are an alternative reliable power solution

The emergency standby generator market provides back-up power to a utility power source to ensure an uninterrupted power supply. A stationary standby generator is permanently installed outside a home, business or manufacturing facility. When primary utility power fails, the generator automatically starts and provides electricity until utility power returns. Portable generators are used where a permanent back-up power source is impractical. We estimate that the generator market in the United States and Canada was $3.6 billion in 2008, and the overall global generator market was estimated by Frost and Sullivan to be over $11 billion in 2008.

The cost of outages and the relative affordability of generators have improved their potential return on investment

Compared to the potential cost of power outages, the purchase and installation of back-up power generators is relatively inexpensive, often yielding a short-term positive return on investment for commercial and industrial consumers. According to a report published by LBNL (as defined on page 70), the total estimated cost of power outages was $57 billion and $20 billion for commercial and industrial consumers, respectively. The increased availability of natural gas generators that are a lower cost solution than traditional diesel generators has improved the return on investment in back-up power for these consumers. In the residential market, the decline in product prices over the last decade has significantly decreased the cost of backup power.

Low penetration in residential and light commercial markets and opportunities for increased penetration in industrial market

There is a substantial opportunity for penetration in the residential standby market, since we estimate penetration to be approximately 2% of U.S. single-family, detached, owner-occupied households with a home value of over $100,000, as defined by the U.S. Census Bureau. This low penetration, when coupled with demographic and lifestyle changes and increasing reliance on home electronics over the last decade, represents a significant opportunity for growth. We believe that each 1% of U.S. household penetration potentially represents up to an approximate $2 billion market opportunity at current product pricing. The portable generator market, with a penetration rate that we estimate to be 10% to 15%, also offers opportunities for growth. The light commercial market includes over two million potential customer locations in the United States. Even in the more mature industrial market, we believe there are additional opportunities for penetration, especially given the benefits provided by natural gas engines over more common diesel engine based generators.

2

Table of Contents

Demographic trends lead to an increased focus on the safety and security provided by standby generators

We believe favorable consumer demographic trends provide opportunities for growth for automatic home standby generators. We believe that demographic changes may lead to an increase in demand as the U.S. population ages and becomes increasingly conscious of safety issues, focused on convenience and dependent on electronic devices. According to our warranty registration data, currently over 70% of home standby generators are purchased by consumers over 50 years of age.

Opportunities for international expansion

The international market represents a significant opportunity for growth in the sale of generators. Market growth rates in Latin America in 2010 range from 8% to 9% in Argentina and Chile to 14% to 15% in Colombia and Mexico, as estimated by Frost and Sullivan. Other international markets are also expected to grow, such as Russia (by 10% annually through 2011) and China (by approximately 14% by 2015). With less than 1% of our 2008 net sales from markets outside the United States and Canada, international sales represent a significant growth opportunity for us.

Regulatory changes should lead to growth in the commercial and industrial standby markets

Federal, state and local governmental authorities have proposed and passed legislation requiring the use of generators within some segments of the industrial and light-commercial markets. Building, health and safety codes often require back-up standby generators in municipal and government buildings and health care facilities, typically for crucial applications such as life support systems, safe building egress or critical equipment functionality. Additionally, increased federal regulation of diesel engine emissions and increased municipal regulation of diesel fuel storage should encourage market growth for natural gas-powered standby generators.

Potential benefits from infrastructure spending programs and recovery in the non-residential construction market

The American Recovery and Reinvestment Act passed in February 2009 provides for $130 billion of construction-related spending for a wide range of projects, including federal buildings and hospitals. We believe that the industrial generator market should benefit from this infusion of funds. After the current downturn in non-residential construction in the United States, the Rosen Consulting Group estimates that spending in this sector will recover after 2010 and increase by 12.5% to $315 billion in 2011 and increase by another 20.6% to $380 billion in 2012. Any such recovery should provide additional marketing opportunities for our light commercial and industrial generator business.

Our competitive strengths

We believe that the following strengths contribute to our being a leading generator manufacturer and will allow us to further capitalize on growth opportunities in our industry:

Significant market share with opportunities for further penetration

We enjoy a leading industry market position with a significant market share in the United States and Canada and opportunities for future penetration. In the residential standby

3

Table of Contents

generator market, we believe we are the market leader with a market share that we estimate to be approximately 70%. We believe that we will have opportunities for growth in this market as spending on new homes and construction recovers and consumer awareness of the benefits of standby generators grows. We believe we also hold strong positions in the light-commercial and industrial markets with an 8% overall market share and a higher share in certain end markets. We believe we will experience growth in these markets as potential end-users recognize that our modular power systems and our natural gas engine platforms provide increased efficiency, affordability and flexibility.

Multi-layered distribution model

The majority of standby power systems are installed by an experienced contractor. As a result, having a network of experienced dealers who can sell, manage the installation of, and service the generator is important. We believe that our multi-layered distribution model gives us an advantage over competitors who do not have as broad a distribution network and generally rely on a single channel to market and sell their products. We use direct dealers for residential, light-commercial and industrial end-users, as well as wholesale, private label, retail, e-commerce and catalog distribution channels, enabling us to reach a broad range of customers. We are constantly developing the scope and strength of our dealer networks, comprised of over 3,700 dealers, and we have trained over 10,000 technicians on our products over the last three years alone. We also sell our products to electrical wholesale distributors, through several private label arrangements with HVAC or electrical equipment and construction machinery companies and through top retailers and e-commerce companies. Finally, our direct-to-national accounts strategy provides a direct, coordinated sales approach for our large customers.

Broadest product line in the industry

Our product offerings include a comprehensive selection of standby and portable generators of various sizes and types with ranges of power output capable of catering to many end markets and users. Our product portfolio includes generators powered by gasoline, diesel, liquid propane and natural gas as well as a combination of diesel and natural gas, or Bi-Fuel™ systems. We also manufacture a complete line of automatic transfer switches, which we pair with our generators to create a complete back-up power system. We believe that our broad product line provides us with a competitive advantage because dealers and distributors prefer dealing with a single source for a broad range of their standby and portable generator needs.

Engineering excellence

Our primary focus on generators drives technological innovation, specialized engineering and manufacturing competencies and distinguishes us from other engine and generator manufacturers. We currently operate three advanced facilities and employ over 100 engineers focused on new product development, existing product improvement and cost reduction. Our commitment to research and development has resulted in a portfolio of approximately 50 U.S. and international patents and patent applications, and various trademark registrations and applications. Examples of our technological advancements include our technology concerning Bi-Fuel™ and our Modular Power Systems, or MPS, technology.

Low-cost producer

We believe that our product engineering, manufacturing and sourcing capabilities, along with our production volume, have enabled us to be one of the lowest-cost producers in the industry.

4

Table of Contents

We have implemented lean manufacturing initiatives and designed our production facilities to quickly adapt to customer demand and to the development of new product offerings. As part of our sourcing strategy, we have developed a network of reliable, low-cost suppliers in the United States and abroad, a network which cannot be easily replicated. Our volume requirements and leading market position generally enable us to obtain favorable terms from our suppliers. In 2009 to date, we sourced more than half of our product components from outside the United States through foreign suppliers with whom we have built strong relationships.

Financial flexibility and strong free cash flow generation

Our flexible cost structure and low-cost global sourcing have contributed to our financial strength and strong cash flow generation. Our variable cost structure enables us to respond quickly to varying market environments. Furthermore, our business model generally requires low capital expenditures with amounts that have averaged less than $9 million per year for each of the last three years. In addition, due to a tax election we made at the time of the CCMP Transactions described below, we expect to have $122 million in annual amortization deductions of intangibles for tax purposes through 2020, which can be used to reduce any cash tax obligations. Any additional cash tax obligations may be further reduced by our $131 million balance of net operating losses as of December 31, 2008.

Experienced management team with substantial equity stake

Our senior management team has significant generator industry experience and a strong track record with a combined total of over 100 years of industry and related experience. This team has been highly successful at expanding our product line, distribution channels and technology leadership, positioning our business for growth through innovation. We expect that upon consummation of this offering, members of our senior management team will own approximately             % of our outstanding common stock on a fully-diluted basis.

Our strategy

We believe we can capitalize on our competitive strengths to grow our business through the following strategies:

Further develop domestic distribution and sales channels

We intend to further expand our geographic and product markets in North America by continuing to develop our dealer network. We have recruited over 600 new dealers in 2009, and we have trained over 10,000 technicians on our products over the last three years. We believe that our dedicated training program helps us attract and retain the most profitable dealers. We also continue to explore strategic partnerships to expand our distribution reach. In addition, we target homebuilders, who represent an attractive sales opportunity given the current under-penetration of generators in newly constructed homes. Through our national accounts program, we target commercial and industrial customers with the potential for large generator purchasing programs. In the light commercial market, we are focusing on opportunities to grow our existing customer base while increasing penetration in non-traditional end markets, such as smaller health care facilities, nursing homes, pharmacies and convenience stores. We are also developing relationships with engineering firms that influence generator purchasing decisions on many industrial projects.

5

Table of Contents

Increase awareness of standby power solutions

We believe that through our extensive dealer network, our private label partnerships and our targeted marketing initiatives, potential customers are becoming increasingly aware of the benefits of standby power solutions. Ten years ago, stationary standby generators were available only at select dealers. Today, standby generators can be purchased at more than 9,000 retail locations, 1,700 electrical wholesale outlets and through over 3,700 Generac dealers and our private label partners. In addition, when power outage events occur, potential customers become increasingly aware of the advantages of generators as reliable sources of back-up electrical power, in the affected area and beyond. Through our targeted marketing initiatives, we seek to increase customer awareness of our products and to further develop Generac® as the leading brand in the standby power market.

Focus on innovation and product development

We intend to continue to provide innovative and affordable products to all of our customers. For instance, in the industrial market, we market our proprietary MPS technology, which provides increased affordability, redundancy and scalability within the 600kW to 9,000kW output ranges when compared to single-engine generators. We have developed a line of natural gas-powered generators, with proprietary fuel systems, emissions technology and control systems, which provide an affordable standby power solution for the light commercial market without the fuel storage, environmental or odor concerns of traditional diesel units. Our XG line of portable generators was recently named as an Editor's Choice by Popular Mechanics magazine. We intend to use our engineering expertise and experience to continue to respond to the evolving demands of our customers.

Further develop international distribution opportunities

With less than 1% of our 2008 net sales from markets outside of the United States and Canada, international sales represent a significant growth opportunity for us. We have focused our initial international sales efforts developing distribution in Mexico and Central and South America. To further penetrate these and other international markets, we are actively pursuing partnerships with established international companies with complementary products and distribution capabilities.

Expand product offering in complementary markets

We believe that the portable generator market represents an attractive opportunity to sell products that are strategic to our customer base and complementary to our manufacturing capabilities, and we therefore re-entered the portable generator market following the expiration of a non-competition agreement in 2007. We introduced an expanded line of portable generators in 2008 and have subsequently added significant distribution capacity, providing us increased opportunities to sell both portable and standby generators. We expect to continuously evaluate opportunities to expand organically or through opportunistic acquisitions into other complementary engine-driven products where we can leverage our manufacturing and sourcing capabilities, technological expertise and strength in distribution.

6

Table of Contents

Risks associated with our business

Our business is subject to numerous risks, as discussed more fully in the section entitled "Risk factors" beginning on page 16 of this prospectus, which you should read in its entirety. In particular:

•

Demand for our products is significantly affected by unpredictable major power outage events that can lead to substantial variations in, and uncertainties regarding, our financial results from period to period;

•

Demand for our standby generators is significantly affected by durable goods spending by consumers and businesses and other macroeconomic conditions;

•

Decreases in the availability, or increases in the cost, of raw materials and key components we use could materially reduce our earnings;

•

The industry in which we compete is highly competitive, and our failure to compete successfully could adversely affect our results of operations and financial condition;

•

Our industry is subject to technological change, and our failure to continue developing new and improved products and to bring these products rapidly to market could have an adverse impact on our business;

•

We rely on independent dealers and distribution partners, and the loss of these dealers and distribution partners, or of any of our sales arrangements with significant private label, telecommunications or retail customers, would adversely affect our business;

•

Our business could be negatively impacted if we fail to adequately protect our intellectual property rights or if third parties claim that we are in violation of their intellectual property rights;

•

Our operations are subject to various environmental, health and safety laws and regulations, and non-compliance with or liabilities under such laws and regulations could result in substantial costs, fines, sanctions and claims;

•

Our products are subject to substantial government regulation;

•

We have a substantial amount of indebtedness, which may adversely affect our cash flow and our ability to operate our business, remain in compliance with debt covenants and make payments on our indebtedness; and

•

After this offering, our principal stockholder will continue to have substantial control over us.

Principal stockholder

In November 2006, affiliates of CCMP Capital Advisors, LLC, or CCMP, together with affiliates of Unitas Capital Ltd., or Unitas, and members of our management, formed Generac and, through Generac, acquired all of the capital stock of Generac Power Systems, Inc., or Generac Power Systems. After this offering, affiliates of CCMP will collectively own approximately             % of our outstanding common stock. For more information, see "CCMP transactions."

7

Table of Contents

CCMP is a leading global private equity firm specializing in buyouts and growth equity investments in companies ranging from $500 million to more than $3 billion in size. CCMP's founders have invested over $12 billion since 1984, which includes their activities at J.P. Morgan Partners, LLC (a private equity division of JPMorgan Chase & Co.) and its predecessor firms. CCMP was formed in August 2006 when the buyout and growth equity investment professionals of J.P. Morgan Partners, LLC separated from JPMorgan Chase & Co. to commence operations as an independent firm. CCMP's latest fund, CCMP Capital Investors II, L.P., closed in September 2007 with commitments of approximately $3.38 billion. The foundation of CCMP's investment approach is to leverage the combined strengths of its deep industry expertise and proprietary global network of relationships by focusing on five targeted industries (Consumer, Retail and Services; Energy; Healthcare Infrastructure; Industrials; and Media and Telecom).

Corporate reorganization

Prior to the consummation of this offering and after giving effect to a                           for one reverse Class A Common Stock split:

•

our Class B Common Stock will convert automatically into an aggregate of             shares of our Class A Common Stock;

•

our Series A Preferred Stock will convert automatically into an aggregate of             shares of our Class A Common Stock; and

•

our Class A Common Stock will be reclassified as common stock.

We refer to the transactions listed above as the "Corporate Reorganization."

For more information, see "Management's discussion and analysis of financial condition and results of operations—Corporate reorganization."

Our executive offices

Generac is a Delaware corporation, which was founded in 2006 and is headquartered in Waukesha, Wisconsin. Generac Power Systems, our principal operating subsidiary, is a Wisconsin corporation founded in 1959. Our principal executive offices are located at S45 W29290 Hwy. 59, Waukesha, Wisconsin 53187. Our main telephone number is (262) 544-4811. Our website address is www.generac.com . None of the information on our website or any other website identified herein is part of this prospectus.

Generac®, Guardian®, Centurion® and Quietsource® are registered trademarks of Generac Power Systems, Inc. All other trademarks and trade names identified in this prospectus, including Bi-Fuel™, are the property of unrelated third parties.

8

Table of Contents

Unless otherwise indicated, the number of shares of common stock to be outstanding after this offering:

•

excludes                  shares of our common stock issuable upon exercise of stock options and shares of restricted stock that we intend to grant to our named executive officers and other employees at the time of this offering, at an exercise price equal to the initial public offering price; and                  shares of our common stock to be reserved for future grants under our Omnibus Plan.

Unless otherwise noted, the information in this prospectus:

•

gives effect to the modification to our capital structure described above under "—Corporate reorganization";

•

assumes no exercise of the underwriters' option to purchase up to                                              additional shares from us; and

•

assumes an initial public offering price of $           per share, the midpoint of the price range set forth on the cover of this prospectus.

9

Table of Contents

Summary historical consolidated financial and other data

The table below provides our summary historical consolidated financial and other data for the periods and as of the dates indicated. The summary historical consolidated financial and other data for the period from January 1, 2006 through November 10, 2006 (Predecessor Period), the period from November 11, 2006 through December 31, 2006 (Successor Period) and the years ended December 31, 2007 and 2008 are derived from our audited consolidated financial statements for such periods included elsewhere in this prospectus. The summary historical consolidated financial and other data for the nine months ended September 30, 2008 and 2009 are derived from our unaudited condensed consolidated financial statements included elsewhere in this prospectus. In the opinion of management, the unaudited condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements and include all adjustments, consisting of normal recurring adjustments, necessary for a fair presentation of our operating results and financial position for those periods and as of such dates. The results for any interim period are not necessarily indicative of the results that may be expected for a full year.

The summary historical consolidated financial data for the twelve months ended September 30, 2009, which are unaudited, have been calculated by subtracting the data for the nine months ended September 30, 2008 from the data for the year ended December 31, 2008, and adding the data for the nine months ended September 30, 2009. This presentation is not in accordance with U.S. GAAP.

In November 2006, affiliates of CCMP, together with affiliates of Unitas and members of our management formed Generac and, through Generac, acquired all of the capital stock of Generac Power Systems. See "CCMP transactions." Generac in all periods prior to November 2006 is referred to as "Predecessor," and in all periods including and after such date is referred to as "Successor." As a result of purchase accounting adjustments associated with the CCMP Transactions, the consolidated financial statements for all Successor periods may not be comparable to those of the Predecessor Period.

The results indicated below and elsewhere in this prospectus are not necessarily indicative of our future performance. You should read this information together with "Selected historical consolidated financial data," "Capitalization," "Management's discussion and analysis of financial condition and results of operations" and our consolidated financial statements and related notes included elsewhere in this prospectus.

10

Table of Contents

11

Table of Contents

12

Table of Contents

13

Table of Contents

14

Table of Contents

15

Table of Contents

Risk factors

An investment in our common stock involves a high degree of risk. You should carefully consider the following risks, as well as the other information contained in this prospectus, before making an investment decision. If any of the following risks, as well as other risks and uncertainties that are not yet identified or that we currently think are immaterial, actually occur, our business, results of operations or financial condition could be materially and adversely affected. In such an event, the trading price of our common stock could decline and you could lose part or all of your investment.

Risks related to our business and industry

Demand for our products is significantly affected by unpredictable major power-outage events that can lead to substantial variations in, and uncertainties regarding, our financial results from period to period.

Sales of our products are subject to consumer buying patterns, and demand for our products is affected by weather-driven and other outage events, including thunderstorms, hurricanes, ice storms and blackouts caused by grid reliability issues. Sustained periods without major power disruptions can lead to reduced consumer awareness of the benefits of standby and portable generator products and can result in reduced sales and excess inventory. For example, in 2007, our net sales declined significantly from the prior year, and this decline was driven in part by the fact that the storm seasons in the two years leading up to and including 2007 resulted in fewer power outages than in the prior years. The lack of major power-outage events can affect our net sales in the quarters following a given storm season. Unpredictable fluctuations in demand are therefore part of managing our business, and these fluctuations could have an adverse effect on our net sales and profits.

Demand for our standby generators is significantly affected by durable goods spending by consumers and businesses and other macroeconomic conditions.

Our business is affected by general economic conditions, and uncertainty or adverse changes such as the recent downturn in worldwide economic conditions and the impact of the credit crisis could lead to a significant decline in demand for our products and pressure to reduce our prices. Our sales of light commercial and industrial generators are affected by conditions in the non-residential construction sector and by the capital investment trends for small and large businesses and municipalities. For example, lower capital spending by our industrial national account and other industrial and commercial customers caused an 8.5% decline in net sales to the industrial and commercial market in the nine months ended September 30, 2009. If these businesses and municipalities cannot access credit markets or do not utilize discretionary funds to purchase our products as a result of the economy or other factors, our business could suffer. In addition, consumer confidence and home remodeling expenditures have a significant impact on sales of our residential products, and prolonged periods of weakness in consumer durable goods spending could have a material impact on our business. Typically, we do not have contracts with our customers, and we cannot guarantee that our current customers will continue to purchase our products. If general economic conditions or consumer confidence were to worsen, or if the non-residential construction sector or rate of capital investments were to decline, our net sales and profits would likely be adversely affected.

16

Table of Contents

Decreases in the availability, or increases in the cost, of raw materials and key components we use could materially reduce our earnings.

The principal raw materials that we use to produce our generators are steel, copper and aluminum. We also source a significant number of component parts that we utilize to manufacture our generators from third parties. The prices of those raw materials and components are susceptible to significant fluctuations due to trends in supply and demand, transportation costs, government regulations and tariffs, price controls, economic conditions and other unforeseen circumstances beyond our control. We do not have long-term supply contracts in place to ensure the raw materials and components we use are available in necessary amounts or at fixed prices. If we are unable to mitigate raw material or component price increases through product design improvements, price increases to our customers or hedging transactions, our profitability could be adversely affected. For example, in 2008, we experienced a 4.8% decrease in gross margin percentage, partially due to increases in commodity prices, including steel, copper and aluminum. Also, our ability to continue to obtain materials and components is subject to the continued reliability and viability of our suppliers, including in some cases, suppliers who are the sole source of important components. If we are unable to obtain adequate, cost efficient or timely deliveries of required raw materials and components, we may be unable to manufacture sufficient quantities of products on a timely basis. This could cause us to lose sales, incur additional costs, delay new product introductions or suffer harm to our reputation.

The industry in which we compete is highly competitive, and our failure to compete successfully could adversely affect our results of operations and financial condition.

We operate in markets that are highly competitive. Some of our competitors have established brands and are larger in size or are divisions of large diversified companies and have substantially greater financial resources. Some of our competitors may be willing to reduce prices and accept lower margins in order to compete with us. In addition, we could face new competition from large international or domestic companies with established industrial brands that enter the generator market. Demand for our products may also be affected by our ability to respond to changes in design and functionality, to respond to downward pricing pressure, and to provide shorter lead times for our products than our competitors. If we are unable to respond successfully to these competitive pressures, we could lose market share, which would have an adverse impact on our results. For more information, see "Business—Competition."

Our industry is subject to technological change, and our failure to continue developing new and improved products and to bring these products rapidly to market could have an adverse impact on our business.

New products, or refinements and improvements of existing products, may have technical failures, their introduction may be delayed, they may have higher production costs than originally expected or they may not be accepted by our customers. If we are not able to anticipate, identify, develop and market high quality products in line with technological advancements that respond to changes in customer preferences, demand for our products could decline and our operating results could be adversely affected.

17

Table of Contents

We rely on independent dealers and distribution partners, and the loss of these dealers and distribution partners, or of any of our sales arrangements with significant private label, telecommunications or retail customers, would adversely affect our business.

In addition to our direct sales force and manufacturer sales representatives, we depend on the services of independent distributors and dealers to sell our products and provide service and aftermarket support to our customers. We also rely upon our distribution channels to drive awareness for our product categories and our brands. In addition, we sell our products to our customers through private label arrangements with leading HVAC equipment, electrical equipment and construction machinery companies, arrangements with top retailers and our direct national accounts with telecommunications and industrial customers. Our distribution agreements and any contracts we have with large telecommunications, retail and other customers are typically not exclusive, and many of the distributors and customers with whom we do business offer products and services of our competitors. Impairment of our relationships with our distributors, dealers or large customers, loss of a substantial number of these distributors or dealers or of one or more large customers, or an increase in our distributors' or dealers' sales of our competitors' products to our customers or of our large customers' purchases of our competitors' products could materially reduce our sales and profits. Also, our ability to successfully realize our growth strategy is dependent in part on our ability to identify, attract and retain new distributors at all layers of our distribution platform, and we cannot be certain that we will be successful in these efforts.

Our business could be negatively impacted if we fail to adequately protect our intellectual property rights or if third parties claim that we are in violation of their intellectual property rights.

We view our intellectual property rights, including those relating to our Generac® brand name, fuel management systems and MPS technology, as important assets. We seek to protect our intellectual property rights through a combination of patent, trademark, copyright and trade secret laws, as well as licensing and confidentiality agreements. These protections may not be adequate to prevent third parties from using our intellectual property without our authorization, breaching any confidentiality agreements with us, copying or reverse engineering our products, or developing and marketing products that are substantially equivalent to or superior to our own. The unauthorized use of our intellectual property by others could reduce our competitive advantage and harm our business. If it became necessary for us to litigate to protect these rights, any proceedings could be burdensome and costly and we may not prevail. We cannot guarantee that any patents, issued or pending, will provide us with any competitive advantage or will not be challenged by third parties. Moreover, the expiration of our patents may lead to increased competition with respect to certain products.

In addition, we cannot be certain that we do not or will not infringe third parties' intellectual property rights. Any such claim, even if it is without merit, may be expensive and time-consuming to defend, subject us to damages, cause us to cease making, using or selling certain products that incorporate the disputed intellectual property, require us to redesign our products, divert management time and attention and/or require us to enter into costly royalty or licensing arrangements.

18

Table of Contents

Our operations are subject to various environmental, health and safety laws and regulations, and non-compliance with or liabilities under such laws and regulations could result in substantial costs, fines, sanctions and claims.

Our operations are subject to a variety of foreign, federal, state and local environmental, health and safety laws and regulations including those governing, among other things, emissions to air, discharges to water, noise, the generation, handling, storage, transportation, treatment and disposal of waste and other materials. In addition, under federal and state environmental laws, we could be required to investigate, remediate and/or monitor the effects of the release or disposal of materials both at sites associated with past and present operations and at third-party sites where wastes generated by our operations were disposed. This liability may be imposed retroactively and whether or not we caused, or had any knowledge of, the existence of these materials and may result in our paying more than our fair share of the related costs. Violations of or liabilities under such laws and regulations could result in substantial costs, fines and civil or criminal proceedings or personal injury and workers' compensation claims.

Our products are subject to substantial government regulation.

Our products are subject to extensive statutory and regulatory requirements governing, among other things, emissions and noise, including standards imposed by the federal Environmental Protection Agency, or EPA, state regulatory agencies, such as the California Air Resources Board, or CARB, and other regulatory agencies around the world. These laws are constantly evolving and many are becoming increasingly stringent. Changes in applicable laws or regulations, or in the enforcement thereof, could require us to redesign our products and could adversely affect our business or financial condition in the future. Developing and marketing products to meet such new requirements could result in substantial additional costs that may be difficult to recover in some markets. In some cases, we may be required to modify our projects or develop new products to comply with new regulations, particularly those relating to air emissions. For example, we were required to modify our natural gas and liquid propane-fueled engines and generators by January 1, 2009 to comply with emissions standards in the United States. While we have been able to meet previous deadlines, failure to comply with other existing and future regulatory standards could adversely affect our position in the markets we serve.

We may incur costs and liabilities as a result of product liability claims.

We face a risk of exposure to product liability claims in the event that the use of our products is alleged to have resulted in injury or other damage. Although we currently maintain product liability insurance coverage, we may not be able to obtain such insurance on acceptable terms in the future, if at all, or obtain insurance that will provide adequate coverage against potential claims. Product liability claims can be expensive to defend and can divert the attention of management and other personnel for long periods of time, regardless of the ultimate outcome. An unsuccessful product liability defense could have a material adverse effect on our financial condition, and results of operations. In addition, we believe our business depends on the strong brand reputation we have developed. If our reputation is damaged, we may face difficulty in maintaining our market share and pricing with respect to some of our products, which would reduce our sales and profitability.

19

Table of Contents

The loss of any key members of our senior management team or key employees could disrupt our operations and harm our business.

Our success depends, in part, on the efforts of certain key individuals, including the members of our senior management team, who have significant experience in the generator industry. If, for any reason, our senior executives do not continue to be active in management, or if our key employees leave our company, our business, financial condition or results of operations could be adversely affected. Failure to continue to attract these individuals at reasonable compensation levels could have a material adverse effect on our business, liquidity and results of operations. Although we do not anticipate that we will have to replace any of these individuals in the near future, the loss of the services of any of our key employees could disrupt our operations and have a material adverse effect on our business.

Disruptions caused by labor disputes or organized labor activities could harm our business.

Currently, less than 3% of our workforce is a member of a labor union. In addition, we may from time to time experience union organizing activities in our non-union facilities. Disputes with the current labor union or new union organizing activities could lead to work slowdowns or stoppages and make it difficult or impossible for us to meet scheduled delivery times for product shipments to our customers, which could result in loss of business. In addition, union activity could result in higher labor costs, which could harm our financial condition, results of operations and competitive position.

We may experience material disruptions to our manufacturing operations.

While we seek to operate our facilities in compliance with applicable rules and regulations and take measures to minimize the risks of disruption at our facilities, a material disruption at one of our manufacturing facilities could prevent us from meeting customer demand, reduce our sales and/or negatively impact our financial results. Any of our manufacturing facilities, or any of our machines within an otherwise operational facility, could cease operations unexpectedly due to a number of events, including:

•

equipment or information technology infrastructure failure;

•

disruptions in the transportation infrastructure including roads, bridges, railroad tracks;

•

fires, floods, earthquakes, or other catastrophes; and

•

other operational problems.

In addition, all of our manufacturing and production facilities are located in Wisconsin within a 30-mile radius. We could experience prolonged periods of reduced production due to unforeseen events occurring in or around our manufacturing facilities in Wisconsin. In the event of a business interruption at our Wisconsin facilities, we may be unable to shift manufacturing capabilities to alternate locations, accept materials from suppliers or meet customer shipment needs, among other severe consequences. Such an event could have a material and adverse impact on our financial condition and results of our operations.

A significant portion of our purchased components are sourced in foreign countries, exposing us to additional risks that may not exist in the United States.

20

Table of Contents

We source a significant portion of our purchased components overseas, primarily in Asia. Our international sourcing subjects us to a number of potential risks in addition to the risks associated with third-party sourcing generally. Such risks include:

•

inflation or changes in political and economic conditions;

•

unstable regulatory environments;

•

changes in import and export duties;

•

domestic and foreign customs and tariffs;

•

currency rate fluctuations;

•

trade restrictions;

•

labor unrest;

•

logistical and communications challenges; and

•

other restraints and burdensome taxes.

These factors may have an adverse effect on our ability to source our purchased components overseas. In particular, if the U.S. dollar were to depreciate significantly against the currencies in which we purchase raw materials from foreign suppliers, our cost of goods sold could increase materially, which would adversely affect our results of operations.

As a U.S. corporation that sources components in foreign countries, we are subject to the Foreign Corrupt Practices Act. A determination that we violated this act may affect our business and operations adversely.

As a U.S. corporation, we are subject to the regulations imposed by the U.S. Foreign Corrupt Practices Act, or the FCPA, which generally prohibits U.S. companies and their intermediaries from making improper payments to foreign officials for the purpose of obtaining or keeping business. Any determination that we have violated the FCPA could have a material adverse effect on our financial position, operating results and cash flows.

We have significant tax assets, usage of which may be subject to limitations in the future.

As of December 31, 2008, we had $131 million of net operating losses for U.S. federal income tax purposes. While this offering of our common stock will not result in a change of control under Section 382 of the U.S. Internal Revenue Code of 1986, any subsequent accumulations of common stock ownership leading to a change of control under that section, including through sales of stock by large stockholders after this offering, all of which are out of our control, could limit our ability to utilize our net operating losses to offset future federal income tax liabilities.

Our total assets include goodwill and other indefinite-lived intangibles. If we determine these have become impaired in the future, net income could be materially adversely affected.

Goodwill represents the excess of cost over the fair market value of net assets acquired in business combinations. Indefinite-lived intangibles are comprised of certain trade names. At September 30, 2009, goodwill and other indefinite-lived intangibles totaled $665.9 million, most of which arose from the CCMP Transactions. We review goodwill and other intangibles at least annually for impairment and any excess in carrying value over the estimated fair value is charged to the results of operations. A reduction in net income resulting from the write-down or impairment of goodwill or indefinite-lived intangibles could have a material adverse effect on our financial statements. For example, in October 2008, due to an increase in our weighted average cost of capital and lower comparable public company market values resulting from

21

Table of Contents

weakening economic conditions, we determined that an impairment of goodwill existed and recorded a non-cash charge of $503.2 million in 2008.

Goodwill and identifiable intangible assets are recorded at fair value on the date of acquisition. In accordance with FASB ASC (Accounting Standards Codification) Topic 350-20, goodwill and indefinite lived intangibles are reviewed at least annually for impairment and definite-lived intangible assets are reviewed for impairment whenever events or changes in circumstances indicate that their carrying value may not be recoverable. Future impairment may result from, among other things, deterioration in the performance of the acquired business or product line, adverse market conditions and changes in the competitive landscape, adverse changes in applicable laws or regulations, including changes that restrict the activities of the acquired business or product line, and a variety of other circumstances. The amount of any impairment is recorded as a charge to the statement of operations. We may never realize the full value of our intangible assets. Any future determination requiring the write-off of a significant portion of intangible assets would have an adverse effect on our financial condition and results of operations. See "Management's discussion and analysis of financial condition and results of operations" for details.

We may need additional capital to finance our growth strategy or to refinance our existing credit facilities, and we may not be able to obtain it on acceptable terms, or at all, which may limit our ability to grow.

We may require additional financing to expand our business. Financing may not be available to us or may be available to us only on terms that are not favorable. The terms of our senior secured credit facilities limit our ability to incur additional debt. In addition, economic conditions, including any further downturn or crisis in the credit markets, could impact our ability to finance our growth on acceptable terms or at all. If we are unable to raise additional funds or obtain capital on acceptable terms, we may have to delay, modify or abandon some or all of our growth strategies. Our revolving credit facility matures in November 2012, our first lien term loan facility matures in November 2013 and our second lien term loan facility matures in May 2014. If we are unable to refinance these facilities on acceptable terms, our liquidity could be adversely affected.

We have a recent history of net losses.

We have incurred net losses during the periods following the CCMP Transactions. For the Successor Period of 2006 and the years ended December 31, 2007 and 2008, we incurred net losses of $16.0 million, $9.7 million and $556.0 million (includes a non-cash goodwill and trade name impairment charge of $583.5 million), respectively. Achieving profitability depends upon numerous factors, including our ability to generate increased net sales and our ability to control expenses. We can make no assurances that we will achieve profitability, or if we do, that we will be able to sustain or increase profitability in the future. Failure to achieve profitability could have an adverse impact on the trading prices of our common stock.

Risk relating to this offering

Management may invest or spend our net proceeds from this offering in ways that may not yield an acceptable return to you.

Although we plan to use a portion of our net proceeds from this offering to pay down a portion of our first and second lien term loans and to pay fees and expenses associated with

22

Table of Contents

the offering, we also may use a portion of the net proceeds for general corporate purposes. We will have broad discretion as to how we will spend such proceeds, and you will have no advance opportunity to evaluate our decisions and may not agree with the manner in which we spend such proceeds. We may not be successful investing the proceeds from this offering in either our operations or external investments.

We do not anticipate paying dividends on our common stock in the foreseeable future.

We do not anticipate paying any dividends in the foreseeable future on our common stock. We intend to retain all future earnings for the operation and expansion of our business and the repayment of outstanding debt. In addition, the terms of our senior secured credit facilities limit our ability to pay dividends on our common stock. As a result, capital appreciation, if any, of our common stock will be your sole source of gain for the foreseeable future. While we may change this policy at some point in the future, we cannot assure you that we will make such a change. See "Dividend policy."

There has been no prior market for our common stock. The market price for our common stock could be volatile, which could cause the value of your investment to decline.

Prior to this offering, there has been no public market for our common stock, and an active trading market may not develop or be sustained after this offering. The market price for our common stock will vary from the initial public offering price after trading commences, and you may not be able to resell your shares of our common stock at or above the initial offering price. The initial public offering price will be determined by negotiation between us and the underwriters based upon a number of factors and may not be indicative of future market prices for our common stock. This could result in substantial losses for investors. The market price of our common stock may fluctuate significantly in response to a number of factors, some of which are beyond our control. These factors include, but are not limited to:

•

developments in the generator industry;

•

power outages and storms;

•

the availability and cost of raw materials and components;

•

strategic actions by us or our competitors, including the entrance to the market of new competition;

•

our ability to continue to develop our distribution channels;

•

the performance of third-party component suppliers;

•

developments with respect to our brand name, patents and other intellectual property rights;

•

environmental and product safety regulations;

•

new laws or regulations or changes in existing laws or regulations applicable to our business;

•

our ability to manufacture our products to commercial standards;

•

additions or departures of key personnel;

•

labor stoppages or strikes;

•

our operating and financial performance and prospects;

23

Table of Contents

•

our quarterly or annual earnings or those of other companies in our industry;

•

changes in earnings estimates or recommendations by securities analysts;

•

changes in accounting standards, policies, guidance, interpretations or principles;

•

changes in general economic conditions in the United States and global economies or financial markets, including such changes resulting from war or incidents of terrorism; and

•

sales of our common stock by us, our principal stockholders or members of our management team.

In addition, the stock market has recently experienced significant price and volume fluctuations. This volatility has had a significant impact on the trading price of securities issued by many companies, including companies in our industry. The changes frequently occur irrespective of the operating performance of the affected companies. Hence, the trading price of our common stock could fluctuate based upon factors that have little or nothing to do with our business.

Future sales of our common stock may cause our stock price to decline.

If our stockholders sell substantial amounts of our common stock in the public market following this offering, the market price of our common stock could decline. These sales might also make it more difficult for us to sell additional equity securities at a time and price that we deem appropriate. Based on shares outstanding as of                    , 2009, upon completion of this offering, we will have              shares of our common stock outstanding. All of the shares of our common stock sold in this offering will be freely tradable in the public market. The remaining             shares of our common stock will be "restricted securities" as defined in Rule 144 under the Securities Act.

In connection with this offering, we, our executive officers and directors and our significant stockholders have agreed that, subject to limited exceptions, for a period of 180 days from the date of this prospectus, we and they will not, directly or indirectly, offer, sell, offer to sell, contract to sell or otherwise dispose of any shares of our common stock without the prior written consent of J.P. Morgan Securities Inc. and Goldman, Sachs & Co., on behalf of the underwriters, except in limited circumstances. However, J.P. Morgan Securities and Goldman, Sachs & Co., in their sole collective discretion, may release any of the securities subject to these lock-up agreements at any time without notice.

Subject to the lock-up agreements, these             restricted securities may be sold into the public market in the future without registration under the Securities Act to the extent permitted under Rule 144.              shares will be available for sale 180 days after the date of this prospectus pursuant to Rule 144; of these shares, approximately              % would be available for sale under Rule 144, which imposes no volume or other limits. In addition, commencing 180 days after the date of this prospectus, certain stockholders holding             outstanding shares of these restricted securities will have registration rights which could allow those holders to sell their shares freely through a future registration statement filed under the Securities Act.

24

Table of Contents

If securities or industry analysts do not publish research or reports about our business, if they adversely change their recommendations regarding our common stock or if our results of operations do not meet their expectations, our common stock price and trading volume could decline.

The trading market for our common stock will be influenced by the research and reports that industry or securities analysts publish about us or our business. If one or more of these analysts cease coverage of our company or fail to publish reports on us regularly, we could lose visibility in the financial markets, which in turn could cause our stock price or trading volume to decline. Moreover, if one or more of the analysts who cover us downgrade recommendations regarding our stock, or if our results of operations do not meet their expectations, our stock price could decline and such decline could be material.

You will experience immediate and substantial dilution as a result of this offering and may experience additional dilution in the future.

The initial public offering price is substantially higher than the book value per share of our outstanding common stock. As a result, you will incur immediate and substantial dilution of $             per share, based on an assumed public offering price of $             per share, the mid-point of the price range set forth on the cover of this prospectus. For additional information, see the section of this prospectus entitled "Dilution."

As a public company, we will be required to meet periodic reporting requirements under the Securities and Exchange Commission, or SEC, rules and regulations. Complying with federal securities laws as a public company is expensive and we will incur significant time and expense enhancing, documenting, testing and certifying our internal control over financial reporting. Any deficiencies in our financial reporting or internal controls could adversely affect our business and the trading price of our common stock.

SEC rules require that, as a publicly-traded company following completion of this offering, we file periodic reports containing our financial statements within a specified time following the completion of quarterly and annual periods. Prior to this offering, we have not been required to comply with SEC requirements to have our financial statements completed and reviewed or audited within a specified time and, as such, we may experience difficulty in meeting the SEC's reporting requirements. Any failure by us to file our periodic reports with the SEC in a timely manner could harm our reputation and reduce the trading price of our common stock.

As a public company, we will incur significant legal, accounting, insurance and other expenses. The Sarbanes-Oxley Act of 2002, as well as compliance with other rules of the SEC and the New York Stock Exchange, or NYSE, will increase our legal and financial compliance costs and make some activities more time-consuming and costly. Furthermore, once we become a public company, SEC rules require that our chief executive officer and chief financial officer periodically certify the existence and effectiveness of our internal control over financial reporting. Our independent registered public accounting firm will be required, beginning with our Annual Report on Form 10-K for our fiscal year ending on December 31, 2010, to attest to our assessment of our internal control over financial reporting. This process, which we have not undertaken in the past, will require significant documentation of policies, procedures and systems, review of that documentation by our internal accounting staff and our outside auditors and testing of our internal control over financial reporting by our internal accounting staff and our outside independent registered public accounting firm. This process will involve

25

Table of Contents

considerable time and expense, may strain our internal resources and have an adverse impact on our operating costs. We may experience higher than anticipated operating expenses and outside auditor fees during the implementation of these changes and thereafter.

During the course of our testing, we may identify deficiencies that would have to be remediated to satisfy the SEC rules for certification of our internal control over financial reporting. As a consequence, we may have to disclose in periodic reports we file with the SEC significant deficiencies or material weaknesses in our system of internal controls. The existence of a material weakness would preclude management from concluding that our internal control over financial reporting is effective and would preclude our independent auditors from issuing an unqualified opinion that our internal control over financial reporting is effective. In addition, disclosures of this type in our SEC reports could cause investors to lose confidence in our financial reporting and may negatively affect the trading price of our common stock. Moreover, effective internal controls are necessary to produce reliable financial reports and to prevent fraud. If we have deficiencies in our disclosure controls and procedures or internal control over financial reporting, it may negatively impact our business, results of operations and reputation.

Anti-takeover provisions in our amended and restated certificate of incorporation and by-laws could prohibit a change of control that our stockholders may favor and could negatively affect our stock price.

Upon the closing of this offering, provisions in our amended and restated certificate of incorporation and by-laws may make it more difficult and expensive for a third party to acquire control of us even if a change of control would be beneficial to the interests of our stockholders. These provisions could discourage potential takeover attempts and could adversely affect the market price of our common stock. These provisions may also prevent or frustrate attempts by our stockholders to replace or remove our management. For example, our amended and restated certificate of incorporation and by-laws:

•

permit our board of directors to issue preferred stock with such terms as they determine, without stockholder approval;

•

provide that only one-third of the members of the board are elected at each stockholders meeting and prohibit removal without cause;

•

require advance notice for stockholder proposals and director nominations; and

•

contain limitations on convening stockholder meetings.

These provisions make it more difficult for stockholders or potential acquirers to acquire us without negotiation and could discourage potential takeover attempts and could adversely affect the market price of our common stock.

Risks relating to our capital structure

We have a substantial amount of indebtedness, which may adversely affect our cash flow and our ability to operate our business, remain in compliance with debt covenants and make payments on our indebtedness.

We have a significant amount of indebtedness. As of September 30, 2009, we had total indebtedness of $1,091.5 million.

26

Table of Contents

Our substantial level of indebtedness increases the possibility that we may be unable to generate cash sufficient to pay, when due, the principal of, interest on or other amounts due in respect of our indebtedness. Our substantial indebtedness, combined with our lease and other financial obligations and contractual commitments could have other important consequences. For example, it could:

•

make it more difficult for us to satisfy our obligations with respect to our indebtedness, including financial and other restrictive covenants, which could result in an event of default under the agreements governing our indebtedness;

•

make us more vulnerable to adverse changes in general economic, industry and competitive conditions and adverse changes in government regulation;

•

require us to dedicate a substantial portion of our cash flow from operations to payments on our indebtedness, thereby reducing the availability of our cash flows to fund working capital, capital expenditures, acquisitions and other general corporate purposes;

•

limit our flexibility in planning for, or reacting to, changes in our business and the industry in which we operate;

•

place us at a competitive disadvantage compared to our competitors that have less debt; and

•

limit our ability to borrow additional amounts for working capital, capital expenditures, acquisitions, debt service requirements, execution of our business strategy or other purposes.

Any of the above-listed factors could materially adversely affect our business, financial condition, results of operations and cash flows. Furthermore, our interest expense could increase if interest rates increase because debt under our senior secured credit facilities bears interest at a variable rate. If we do not have sufficient earnings to service our debt, we may be required to refinance all or part of our existing debt, sell assets, borrow more money or sell securities, none of which we can guarantee we will be able to do.

The terms of our senior secured credit facilities restrict our current and future operations, particularly our ability to respond to changes in our business or to take certain actions.

Our senior secured credit facilities contain, and any future indebtedness of ours or our subsidiaries would likely contain, a number of restrictive covenants that impose significant operating and financial restrictions on us and our subsidiaries, including restrictions on our ability to engage in acts that may be in our best long-term interests. Our senior secured credit facilities include a financial covenant that requires us not to exceed a maximum total leverage ratio.

Our senior secured credit facilities require us to use a portion of excess cash flow and proceeds of certain asset sales that are not reinvested in our business and other dispositions to repay indebtedness under our senior secured credit facilities.

Our senior secured credit facilities also include covenants restricting, among other things, our ability to:

•

incur liens;

•

incur or assume additional debt or guarantees or issue preferred stock;

27

Table of Contents

•

pay dividends, or make redemptions and repurchases, with respect to capital stock;

•

prepay, or make redemptions and repurchases of, subordinated debt;

•

make loans and investments;

•

make capital expenditures;

•

engage in mergers, acquisitions, asset sales, sale/leaseback transactions and transactions with affiliates;

•

change the business conducted by us or our subsidiaries; and

•

amend the terms of subordinated debt.

The operating and financial restrictions and covenants in our senior secured credit facilities and any future financing agreements may adversely affect our ability to finance future operations or capital needs or to engage in other business activities. A breach of any of the restrictive covenants in our senior secured credit facilities would result in a default under our senior secured credit facilities. If any such default occurs, the lenders under our senior secured credit facilities may elect to declare all outstanding borrowings, together with accrued interest and other fees, to be immediately due and payable, or enforce their security interest, any of which would result in an event of default. The lenders will also have the right in these circumstances to terminate any commitments they have to provide further borrowings.

At September 30, 2008, we failed to satisfy the leverage ratio in our senior secured credit facilities. This default was cured by an equity contribution from affiliates of CCMP. However, CCMP and its affiliates are under no obligation to provide additional funds to us in the event of future covenant defaults.

After this offering, our principal stockholder will continue to have substantial control over us.

After the consummation of this offering, affiliates of CCMP will collectively beneficially own approximately             % of our outstanding common stock and will collectively beneficially own approximately             % of our outstanding common stock if the underwriters' option to purchase additional shares is exercised in full. As a consequence, CCMP or its affiliates will be able to exert a significant degree of influence or actual control over our management and affairs and will control matters requiring stockholder approval, including the election of directors, a merger, consolidation or sale of all or substantially all of our assets, and any other significant transaction. The interests of this stockholder may not always coincide with our interests or the interests of our other stockholders. For instance, this concentration of ownership may have the effect of delaying or preventing a change in control of us otherwise favored by our other stockholders and could depress our stock price.

Because affiliates of CCMP control more than 50% of the voting power of our common stock, we are a "controlled company" within the meaning of the NYSE's Listed Company Manual. Under the NYSE's Listed Company Manual, a controlled company may elect not to comply with certain NYSE corporate governance requirements, including requirements that: (1) a majority of the board of directors consist of independent directors; (2) compensation of officers be determined or recommended to the board of directors by a majority of its independent directors or by a compensation committee that is composed entirely of independent directors;

28

Table of Contents

and (3) director nominees be selected or recommended by a majority of the independent directors or by a nominating committee composed solely of independent directors. Because we have taken advantage of the controlled company exemption to certain NYSE corporate governance requirements, our stockholders do not have the same protections afforded to stockholders of companies that are subject to all of the NYSE corporate governance requirements.

Conflicts of interest may arise because some of our directors are principals of our principal stockholder.

Upon the completion of this offering, representatives of CCMP and its affiliates will occupy a majority of the seats on our board of directors. CCMP or its affiliates could invest in entities that directly or indirectly compete with us or companies in which CCMP or its affiliates are currently invested may already compete with us. As a result of these relationships, when conflicts arise between the interests of CCMP or its affiliates and the interests of our stockholders, these directors may not be disinterested. The representatives of CCMP and its affiliates on our board of directors, by the terms of our amended and restated certificate of incorporation, are not required to offer us any transaction opportunity of which they become aware and could take any such opportunity for themselves or offer it to other companies in which they have an investment, unless such opportunity is expressly offered to them solely in their capacity as our directors.

29

Table of Contents

Forward-looking statements

This prospectus contains forward-looking statements that are subject to risks and uncertainties. All statements other than statements of historical fact included in this prospectus are forward-looking statements. Forward-looking statements give our current expectations and projections relating to our financial condition, results of operations, plans, objectives, future performance and business. You can identify forward-looking statements by the fact that they do not relate strictly to historical or current facts. These statements may include words such as "anticipate," "estimate," "expect," "project," "plan," "intend," "believe," "may," "should," "can have," "likely," "future" and other words and terms of similar meaning in connection with any discussion of the timing or nature of future operating or financial performance or other events.

The forward-looking statements contained in this prospectus are based on assumptions that we have made in light of our industry experience and on our perceptions of historical trends, current conditions, expected future developments and other factors we believe are appropriate under the circumstances. As you read and consider this prospectus, you should understand that these statements are not guarantees of performance or results. They involve risks, uncertainties (some of which are beyond our control) and assumptions. Although we believe that these forward-looking statements are based on reasonable assumptions, you should be aware that many factors could affect our actual financial results and cause them to differ materially from those anticipated in the forward-looking statements. The forward-looking statements contained in this prospectus include estimates regarding:

•

our business, financial and operating results and future economic performance;

•

proposed new product and service offerings; and

•

management's goals, expectations and objectives and other similar expressions concerning matters that are not historical facts.

Factors that could affect our actual financial results and cause them to differ materially from those anticipated in the forward-looking statements include:

•

demand for our products;

•

power outages and storms;

•

availability of raw materials and key components used producing our products;

•

competitive factors in the industry in which we operate;

•

our dependence on our distribution network;

•

our ability to invest in, develop or adapt to changing technologies and manufacturing techniques;

•

changes in environmental, health and safety laws and regulations;

•

loss of our key management and employees;

30

Table of Contents

•

increase in product liability claims; and

•

other factors that are described under "Risk factors."

Should one or more of these risks or uncertainties materialize, or should any of these assumptions prove incorrect, our actual results may vary in material respects from those projected in these forward-looking statements.

Any forward-looking statement made by us in this prospectus speaks only as of the date on which we make it. Factors or events that could cause our actual results to differ may emerge from time to time, and it is not possible for us to predict all of them. We undertake no obligation to update any forward-looking statement, whether as a result of new information, future developments or otherwise, except as may be required by law.

31

Table of Contents

CCMP transactions

In November 2006, affiliates of CCMP, together with affiliates of Unitas and members of our management, purchased an aggregate of $689 million of our equity capital. In addition, on November 10, 2006, Generac Power Systems borrowed an aggregate of $1,380 million, consisting of an initial drawdown of $950 million under a $1.1 billion first lien secured credit facility and $430 million under a $430 million second lien secured credit facility. With the proceeds from these equity and debt financings, together with cash on hand at Generac Power Systems, we (1) acquired all of the capital stock of Generac Power Systems and repaid certain pre-transaction indebtedness of Generac Power Systems for $2.0 billion, (2) paid $66 million in transaction costs related to the transaction and (3) retained $3.0 million for general corporate purposes.

We refer to the foregoing transactions collectively as the "CCMP Transactions."

32

Table of Contents

Use of proceeds

We estimate that the net proceeds to us from our sale of                  shares of our common stock in this offering will be $                  , after deducting underwriting discounts and commissions and estimated expenses payable by us in connection with this offering. This assumes a public offering price of $                   per share, which is the midpoint of the price range set forth on the cover of this prospectus. We intend to use approximately $                  of the net proceeds to pay down a portion of our first and second lien term loans and approximately $                  to pay fees and expenses associated with the offering. We will use the remainder of the net proceeds, if any, for general corporate purposes.

Our first and second lien term loans bear interest at rates based upon either a base rate or adjusted LIBOR rate plus an applicable margin. At September 30, 2009, the interest rates applicable to our first and second lien term loans were 5.7% and 9.2%, respectively. The maturity date for our first and second lien term loans are November 10, 2013 and May 10, 2014, respectively.

A $1.00 increase (decrease) in the assumed initial public offering price of $                  per share would increase (decrease) the net proceeds to us from this offering by $                   million, assuming the number of shares offered by us, as set forth on the cover page of this prospectus, remains the same and after deducting underwriting discounts and commissions and estimated expenses payable by us.

33

Table of Contents

Dividend policy

We have never paid dividends on our common stock. After this offering, we intend to retain all available funds and any future earnings to reduce debt and fund the development and growth of our business, and we do not anticipate paying any dividends on our common stock. However, in the future, subject to the factors described below and our future liquidity and capitalization, we may change this policy and choose to pay dividends. Our ability to pay dividends on our common stock is currently restricted by the terms of our senior secured credit facilities and may be further restricted by any future indebtedness we incur. Our business is conducted through our principal operating subsidiary, Generac Power Systems. Dividends from, and cash generated by Generac Power Systems will be our principal sources of cash to repay indebtedness, fund operations and pay dividends. Accordingly, our ability to pay dividends to our stockholders is dependent on the earnings and distributions of funds from Generac Power Systems.

Any future determination to pay dividends will be at the discretion of our board of directors and will take into account:

•

restrictions in our senior secured credit facilities;

•

general economic and business conditions;

•

our financial condition and results of operations;

•

our capital requirements;

•

the ability of Generac Power Systems to pay dividends and make distributions to us; and

•

such other factors as our board of directors may deem relevant.

See "Management's discussion and analysis of financial condition and results of operations."

34

Table of Contents