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        The following table presents summary consolidated balance sheet data as of the dates indicated:

•

on an actual basis;



•

on a pro forma basis as of September 30, 2009 to give effect to all of the reorganization transactions described in "The Reorganization and Our Holding Company Structure"; and



•

on a pro forma as adjusted basis as of September 30, 2009 to give further effect to our sale of             shares of common stock in this offering at an assumed initial public offering price of $            per share, the midpoint of the range set forth on the cover of this prospectus, after deducting estimated underwriting discounts and commissions and estimated offering expenses.

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RISK FACTORS

        You should consider carefully each of the risks described below, together with all of the other information contained in this prospectus, before deciding to invest in our Class A common stock. If any of the following risks materializes, our business, financial condition and results of operations may be materially adversely affected. In that event, the trading price of our Class A common stock could decline, and you could lose some or all of your investment.

        This prospectus also contains forward-looking statements that involve risks and uncertainties. Actual results could differ materially from those anticipated in these forward-looking statements as a result of various factors, including the risks described below and elsewhere in this prospectus. See "Cautionary Statement Regarding Forward-Looking Statements."

Risks Related to Our Business and the Wind Energy Industry

If we cannot continue to build our pipeline of projects under development and turn them into operating projects, our business will not grow and we may have significant write-offs.

        We may be unable to meet our target of having in excess of 2,000 MW of operating/under-construction capacity by 2014, because we will need to add new projects to our pipeline on an ongoing basis. In addition, we may have difficulty in converting our development pipeline into operating projects or may be unable to find suitable projects to add to our pipeline. These circumstances could prevent those projects from commencing operations or from meeting our original expectations about how much energy they will generate or the returns they will achieve. Since completing the projects in our development pipeline as anticipated or at all involves numerous risks and uncertainties, some projects in our portfolio will not progress to construction or may be substantially delayed. From time to time we have abandoned projects on which we had started development work, or re-categorized projects to a less advanced stage than we had previously assigned them, representing in the aggregate approximately 105 MW of potential capacity. This resulted in $3.5 million and $3.1 million of write-offs in 2008 and 2009, respectively. Abandonment or re-categorization of our projects may make it difficult for us to achieve our operating capacity goals by our target dates. As we increase our development activities and the number of projects in our pipeline, such discontinuations and re-categorizations and the corresponding write-offs may increase. In addition, those projects that are constructed and begin operations may not meet our return expectations due to schedule delays, cost overruns or revenue shortfalls or they may not generate the capacity that we anticipate or result in receipt of revenue in the originally anticipated time period or at all. An inability to maintain our development pipeline or to convert those projects into financially successful operating projects would have a material adverse effect on our business, financial condition and results of operations.

We have generated substantial net losses and negative operating cash flows since our inception and expect to continue to do so as we develop and construct new wind energy projects.

        We have generated substantial net losses and negative operating cash flows from operating activities since our operations commenced. We had accumulated losses of approximately $171.9 million from our inception through September 30, 2009. For the year ended December 31, 2008 and the nine months ended September 30, 2009, we generated net losses of $26.2 million and $47.3 million, respectively. In addition, our operating activities used cash of $41.6 million and $39.7 million for the year ended December 31, 2008 and the nine months ended September 30, 2009, respectively.

        We expect that our net losses will continue and our cash used in operating activities will grow during the next several years, as compared with prior periods, as we increase our development activities and construct additional wind energy projects. Wind energy projects in development typically incur operating losses prior to commercial operation at which point the projects begin to generate positive operating cash flow. We also expect to incur additional costs, contributing to our losses and operating uses of cash, as we incur the incremental costs of operating as a public company. Our costs may also

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increase due to such factors as higher than anticipated financing and other costs; non-performance by third-party suppliers or subcontractors; increases in the costs of labor or materials; and major incidents or catastrophic events. If any of those factors occurs, our losses could increase significantly and the value of our common stock could decline. As a result, our net losses and accumulated deficit could increase significantly.

We depend heavily on federal, state and local government support for renewable energy, especially wind projects.

        We depend heavily on government policies that support renewable energy and enhance the economic feasibility of developing wind energy projects. The federal government and several of the states in which we operate or into which we sell power provide incentives that support the sale of energy from renewable sources, such as wind.

        The Internal Revenue Code provides a production tax credit (PTC) for each kWh of energy generated by an eligible resource. Under current law, an eligible wind facility placed in service prior to the end of 2012 may claim the PTC. The PTC is a credit claimed against the income of the owner of the eligible project.

        PTC eligible projects are also eligible for an investment tax credit (ITC) of 30% of the eligible cost-basis, which is in lieu of the PTC. The same placed-in-service deadline of December 31, 2012 applies for purposes of the ITC. The ITC is a credit claimed against the income of the owner of the eligible project.

        The American Recovery and Reinvestment Act of 2009 (ARRA) created a grant administered by the U.S. Treasury that provides for a cash payment of the amount an eligible project whose construction began in 2010 would otherwise be able to claim under the ITC. In addition, there are various programs for loan guarantees. See "Industry—Drivers of U.S. Wind Energy Growth—State and Federal Government Incentives."

        In addition to federal incentives, we rely on state incentives that support the sale of energy generated from renewable sources, including state adopted renewable portfolio standards (RPS) programs. Such programs generally require that electricity supply companies include a specified percentage of renewable energy in the electricity resources serving a state or purchase credits demonstrating the generation of such electricity by another source. However, the legislation creating such RPS requirements usually grants the relevant state public utility commission the ability to reduce electric supply companies' obligations to meet the RPS requirements in certain circumstances. If the RPS requirements are reduced or eliminated, this could result in our receiving lower prices for our power and in a reduction in the value of our RECs, which could have a material adverse effect on us. See "Industry—Drivers of U.S. Wind Energy Growth—State and Federal Government Incentives."

        We depend heavily on these programs to finance the projects in our development pipeline. If any of these incentives are adversely amended, eliminated, not extended beyond their current expiration dates, or if funding for these incentives is reduced, it would have a material adverse effect on our ability to obtain financing. A delay or failure by federal departments to administer these programs in a timely and efficient manner could have a material adverse effect on our financing.

        While certain federal, state and local programs and policies promote renewable energy and additional legislation is regularly being considered that would enhance the demand for renewable energy, policies may be adversely modified, legislation may not pass or may be amended and governmental support of renewable energy development, particularly wind energy, may not continue or may be reduced. If governmental authorities do not continue supporting, or reduce their support for, the development of wind energy projects, our revenues may be adversely affected, our economic return

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on certain projects may be reduced, our financing costs may increase, it may become more difficult to obtain financing, and our business and prospects may otherwise be adversely affected.

Most of our revenue comes from sales of electricity and RECs, which are subject to market price fluctuations, and there is a risk of a significant, sustained decline in their market prices. Such a decline may make it more difficult to develop our projects.

        We may not be able to develop our projects economically if there is a significant, sustained decline in market prices for electricity or RECs without a commensurate decline in the cost of turbines and the other capital costs of constructing wind energy projects. Electricity prices are affected by various factors and may decline for many reasons that are not within our control. Those factors include changes in the cost or availability of fuel, regulatory and governmental actions, changes in the amount of available generating capacity from both traditional and renewable sources, changes in power transmission or fuel transportation capacity, seasonality, weather conditions and changes in demand for electricity. In addition, other power generators may develop new technologies or improvements to traditional technologies to produce power that could increase the supply of electricity and cause a sustained reduction in market prices for electricity and RECs. If governmental action or conditions in the markets for electricity or RECs cause a significant, sustained decline in the market prices of electricity or those attributes, without an offsetting decline in the cost of turbines or other capital costs of wind energy projects, we may not be able to develop and construct our pipeline of development projects or achieve expected revenues, which could have a material adverse effect on our business, financial condition and results of operations.

The production of wind energy depends heavily on suitable wind conditions. If wind conditions are unfavorable, our electricity production, and therefore our revenue, may be substantially below our expectations.

        The electricity produced and revenues generated by a wind energy project depends heavily on wind conditions, which are variable and difficult to predict. We base our decisions about which sites to develop in part on the findings of long-term wind and other meteorological studies conducted in the proposed area, which measure the wind's speed, prevailing direction and seasonal variations. Actual wind conditions, however, may not conform to the measured data in these studies and may be affected by variations in weather patterns, including any potential impact of climate change. Therefore, the electricity generated by our projects may not meet our anticipated production levels or the rated capacity of the turbines located there, which could adversely affect our business, financial condition and results of operations. Projections of wind resources also rely upon assumptions about turbine placement, interference between turbines and the effects of vegetation, land use and terrain, which involve uncertainty and require us to exercise considerable judgment. We or our consultants may make mistakes in conducting these wind and other meteorological studies. Any of these factors could cause us to develop sites that have less wind potential than we expected, or to develop sites in ways that do not optimize their potential, which could cause the return on our investment in these projects to be lower than expected.

        If our wind energy assessments turn out to be wrong, our business could suffer a number of material adverse consequences, including:

•

our energy production and sales may be significantly lower than we predict;



•

our hedging arrangements may be ineffective or more costly;



•

we may not produce sufficient energy to meet our commitments to sell electricity or RECs and, as a result, we may have to buy electricity or RECs on the open market to cover our obligations or pay damages; and

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•

our projects may not generate sufficient cash flow to make payments of principal and interest as they become due on our project-related debt, and we may have difficulty obtaining financing for future projects.

Natural events may reduce energy production below our expectations.

        A natural disaster, severe weather or an accident that damages or otherwise adversely affects any of our operations could have a material adverse effect on our business, financial condition and results of operations. Lightning strikes, blade icing, earthquakes, tornados, extreme wind, severe storms, wildfires and other unfavorable weather conditions or natural disasters could damage or require us to shut down our turbines or related equipment and facilities, impeding our ability to maintain and operate our facilities and decreasing electricity production levels and our revenues. Operational problems, such as degradation of turbine components due to wear or weather or capacity limitations on the electrical transmission network, can also affect the amount of energy we are able to deliver. Any of these events, to the extent not fully covered by insurance, could have a material adverse effect on our business, financial condition and results of operations.

Operational problems may reduce energy production below our expectations.

        Spare parts for wind turbines and key pieces of electrical equipment may be hard to acquire or unavailable to us. Sources for some significant spare parts and other equipment are located outside of North America. If we were to experience a shortage of or inability to acquire critical spare parts, we could incur significant delays in returning facilities to full operation. In addition, we generally do not hold spare substation main transformers. These transformers are designed specifically for each wind energy project, and the current lead time to receive an order for this type of equipment is over eight months. If we have to replace any of our substation main transformers, we could be unable to sell electricity from the affected wind energy project until a replacement is installed. That interruption to our business might not be fully covered by insurance.

One of our key turbine suppliers, Clipper Windpower Plc, has experienced certain technical issues with its wind turbine technology and may continue to experience similar issues.

        Clipper, one of our two turbine suppliers in our existing operating fleet, is a new entrant into the wind turbine market. Clipper's first prototype wind turbine, the 2.5 MW Liberty, was placed in service in April 2005. We now operate 116 Liberty turbines (290 MW) and plan to install 34 Liberty turbines in 2010 (85 MW). We have entered into agreements which provide us the right but not the obligation to acquire up to 253 Liberty turbines (633 MW) for installation during 2011-2015. We deployed the first eight commercially produced Liberty turbines at our Steel Winds I project, which commenced commercial operations on June 1, 2007. Since our initial deployment, Clipper has announced and remediated three defects affecting the Liberty turbines deployed by us and other customers that resulted in prolonged downtime for turbines at various projects, including our Steel Winds I and Cohocton projects. Among issues adversely affecting Liberty turbine performance were drive trains that incorporated a supplier-related deficiency, a design deficiency resulting in separation of bonding materials in the blades of several turbines and minor defects in the blade skin resulting from a defective manufacturing process. At present, all such items affecting our installed Clipper fleet have been remediated and availability of the Liberty turbines in our fleet is within warranted levels.

        The Liberty turbines, however, may not perform in accordance with Clipper's specifications for their anticipated useful life or may require additional warranty or non-warranty repairs. In addition, the initial failure of performance has adversely affected our ability to arrange and close turbine supply loans, tax equity financing transactions and construction loans involving Liberty turbines. Moreover, Clipper may not be able to fund its obligations to us and its other customers under its outstanding warranty agreements.

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        A failure of Clipper to produce Liberty turbines that perform within design specifications would preclude us from completing projects that could otherwise incorporate Clipper technology and likely result in our determination to elect not to purchase any or all Liberty turbines that we have the right but not the obligation to acquire from 2011 through 2015.

        We have paid Clipper approximately $60 million of deposits and progress payments towards turbine purchases from 2011–2015 and intend to pay approximately $30 million more in deposits and progress payments through January 15, 2011. If we elect for any reason not to acquire any additional turbines from Clipper, we will forfeit the pro rata portion of these deposits and progress payments corresponding to the schedule of future turbine purchases: $38.6 million for turbines scheduled to be purchased in 2011, $17.9 million for 2012, $10.7 million for 2013, $13.4 million for 2014 and $8.9 million for 2015.

        We have no commitments from turbine manufacturers other than Clipper for projects we plan to have in construction after 2010.

A portion of our revenues from the sale of RECs are not hedged, and we are exposed to volatility of commodity prices with respect to those sales.

        REC prices are driven by various market forces, including electricity prices and the availability of electricity from other renewable energy sources and conventional energy sources. We are unable to hedge a portion of our revenues from RECs in certain markets where conditions limit our ability to sell forward all of our RECs. Our ability to hedge RECs generated by our Northeast projects is limited by the unbundled nature of the RECs and the relative illiquidity of this market, and revenues associated with these RECs account for a majority of the unhedged revenue stream from our existing operating fleet. We are exposed to volatility of commodity prices with respect to the portion of RECs that are unhedged, including risks resulting from volatility in commodities, changes in regulations, including state RPS targets, general economic conditions and changes in the level of renewable energy generation. We will have quarterly variations in our revenues from the sale of unhedged RECs.

We have a limited operating history and our rapid growth may make it difficult for us to manage our business efficiently.

        Since we began our business in 2002 and began commercial operation of our first wind energy project in 2006, there is limited history to use to evaluate our business. You should consider our prospects in light of the risks and uncertainties growing companies encounter in rapidly evolving industries such as ours. Also, our rapid growth may make it difficult for us to manage our business efficiently, effectively manage our capital expenditures and control our costs, including general and administrative costs. These challenges could have a material adverse effect on our business, financial condition and results of operation.

We rely on a limited number of key customers.

        There are a limited number of possible customers for electricity and RECs produced in a given geographic location. As a result, we do not have many choices about the buyers of our electricity, which limits our ability to negotiate the terms under which we sell electricity. Also, since we depend on sales of electricity and RECs to certain key customers, our operations are highly dependent upon these customers' fulfilling their contractual obligations under our power purchase agreements (PPAs) and other material sales contracts. For example, 48% of our revenues were generated from sales of electricity under PPAs with three customers in the nine months ended September 30, 2009. Our customers may not comply with their contractual payment obligations or may become subject to insolvency or liquidation proceedings during the term of the relevant contracts. In addition, the credit support we received from such customers to secure their payments under the PPAs may not be

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sufficient to cover our losses if they fail to perform. To the extent that any of our customers are, or are controlled by, governmental entities, they may also be subject to legislative or other political action that impairs their contractual performance. Failure by any key customer to meet its contractual commitments or insolvency or liquidation of our customers could have a material adverse effect on our business, financial condition and results of operations.

We face competition primarily from other renewable energy sources and, in particular, other wind energy companies.

        We believe our primary competitors are developers and operators focused on renewable energy generation, and specifically wind energy companies. Renewable energy sources, including wind, biomass, geothermal and solar, currently benefit from various governmental incentives such as PTCs, ITCs, cash grants, loan guarantees, RPS programs and accelerated tax depreciation. Changes in any of these incentives could significantly disadvantage wind energy generators including us, compared with other renewable energy sources. Further, the energy industry is rapidly evolving and highly competitive. A reduction in demand for energy from renewable sources or our failure to identify and adapt to new technologies could have a material adverse effect on our business, financial condition and results of operations.

        We compete with other wind energy companies primarily for sites with good wind resources that can be built in a cost-effective manner. We also compete for access to transmission or distribution networks. Because the wind energy industry in the United States is at an early stage, we also compete with other wind energy developers for the limited pool of personnel with requisite industry knowledge and experience. Furthermore, in recent years, there have been times of increased demand for wind turbines and their related components, causing turbine suppliers to have difficulty meeting the demand. If these conditions return in the future, turbine and other component manufacturers may give priority to other market participants, including our competitors, who may have resources greater than ours.

        We compete with other renewable energy companies (and energy companies in general) for the financing needed to pursue our development plan. Once we have developed a project and put a project into operation, we may compete on price if we sell electricity into power markets at wholesale market prices. Depending on the regulatory framework and market dynamics of a region, we may also compete with other wind energy companies, as well other renewable energy generators, when we bid on or negotiate for a long-term PPA.

We also compete with traditional energy companies.

        We also compete with traditional energy companies. For example, depending on the regulatory framework and market dynamics of a region, we also compete with traditional electricity producers when we bid on or negotiate for a long-term PPA. Furthermore, technological progress in traditional forms of electricity generation or the discovery of large new deposits of traditional fuels could reduce the cost of electricity generated from those sources and as a consequence reduce the demand for electricity from renewable energy sources, or render existing or future wind energy projects uncompetitive. Any of these developments could have a material adverse effect on our business, financial condition and results of operations.

The growth of our business depends on locating and obtaining control of suitable operating sites.

        Wind energy projects require wind conditions that are found in limited geographic areas and, within these areas, at particular sites. These sites must also be suitable for construction of a wind energy project, including related roads and operations and maintenance facilities. Further, projects must be interconnected to electricity transmission or distribution networks. Once we have identified a suitable operating site, obtaining the requisite land rights (including access rights, setbacks and other

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easements) requires us to negotiate with landowners and local government officials. These negotiations can take place over a long time, are not always successful and sometimes require economic concessions not in our original plans. The property rights necessary to construct and interconnect our projects must also be insurable and otherwise satisfactory to our financing counterparties. In addition, our ability to obtain adequate property rights is subject to competition from other wind energy developers. If a competitor or other party obtains land rights critical to our project development efforts that we are unable to resolve, we could incur losses as a result of development costs for sites we do not develop, which we would have to write off. If we are unable to obtain adequate property rights for a project, including its interconnection, that project may be smaller in size or potentially unfeasible. Failure to obtain insurable property rights for a project satisfactory to our financing counterparties would preclude our ability to obtain third-party financing and could prevent ongoing development and construction of that project.

Negative public or community response to wind energy projects in general or our projects specifically can adversely affect our ability to develop our projects.

        Negative public or community response to our wind energy projects can adversely affect our ability to develop, construct and operate our projects. This type of negative response can lead to legal, public relations and other challenges that impede our ability to meet our development and construction targets, achieve commercial operations for a project on schedule, address the changing needs of our projects over time and generate revenues. Some of our projects are and have been the subject of administrative and legal challenges from groups opposed to wind energy projects in general or concerned with potential environmental, health or aesthetic impacts, impacts on property values or the rewards of property ownership, or impacts on the natural beauty of public lands. We expect this type of opposition to continue as we develop and construct our existing and future projects. An increase in opposition to our requests for permits or successful challenges or appeals to permits issued to us could materially adversely affect our development plans. If we are unable to develop, construct and operate the production capacity that we expect from our development projects in our anticipated timeframes, it could have a material adverse effect on our business, financial condition and results of operations.

We need governmental approvals and permits, including environmental approvals and permits, to construct and operate our projects. Any failure to procure and maintain necessary permits would adversely affect ongoing development, construction and continuing operation of our projects.

        The design, construction and operation of wind energy projects are highly regulated, require various governmental approvals and permits, including environmental approvals and permits, and may be subject to the imposition of related conditions that vary by jurisdiction. In some cases, these approvals and permits require periodic renewal. We cannot predict whether all permits required for a given project will be granted or whether the conditions associated with the permits will be achievable. The denial of a permit essential to a project or the imposition of impractical conditions would impair our ability to develop the project. In addition, we cannot predict whether the permits will attract significant opposition or whether the permitting process will be lengthened due to complexities and appeals. Delay in the review and permitting process for a project can impair or delay our ability to develop that project or increase the cost so substantially that the project is no longer attractive to us. We have experienced delays in developing our projects due to delays in obtaining non-appealable permits and may experience delays in the future. If we were to commence construction in anticipation of obtaining the final, non-appealable permits needed for that project, we would be subject to the risk of being unable to complete the project if all the permits were not obtained. If this were to occur, we would likely lose a significant portion of our investment in the project and could incur a loss as a result. Any failure to procure and maintain necessary permits would adversely affect ongoing development, construction and continuing operation of our projects.

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Our development activities and operations are subject to numerous environmental, health and safety laws and regulations.

        We are subject to numerous environmental, health and safety laws and regulations in each of the jurisdictions in which we operate. These laws and regulations require us to obtain and maintain permits and approvals, undergo environmental impact assessments and review processes and implement environmental, health and safety programs and procedures to control risks associated with the siting, construction, operation and decommissioning of wind energy projects. For example, to obtain permits we could be required to undertake expensive programs to protect and maintain local endangered species. If such programs are not successful, we could be subject to penalties or to revocation of our permits. In addition, permits frequently specify permissible sound levels.

        If we do not comply with applicable laws, regulations or permit requirements, we may be required to pay penalties or fines or curtail or cease operations of the affected projects. Violations of environmental and other laws, regulations and permit requirements, including certain violations of laws protecting migratory birds and endangered species, may also result in criminal sanctions or injunctions.

        Environmental, health and safety laws, regulations and permit requirements may change or become more stringent. Any such changes could require us to incur materially higher costs than we currently have. Our costs of complying with current and future environmental, health and safety laws, regulations and permit requirements, and any liabilities, fines or other sanctions resulting from violations of them, could adversely affect our business, financial condition and results of operations.

Our ownership and operation of real property and our disposal of hazardous waste could result in our being liable for environmental issues.

        Certain environmental laws impose liability on current and previous owners and operators of real property for the cost of removal or remediation of hazardous substances. These laws often impose liability even if the owner or operator did not know of, or was not responsible for, the release of such hazardous substances. They can also assess liability on persons who arrange for hazardous substances to be sent to disposal or treatment facilities when such facilities are found to be contaminated. Such persons can be responsible for cleanup costs even if they never owned or operated the contaminated facility. In addition to actions brought by governmental agencies, private plaintiffs may also bring claims arising from the presence of hazardous substances on a property or exposure to such substances. Our liabilities arising from past or future releases of, or exposure to, hazardous substances may adversely affect our business, financial condition and results of operations.

We often rely on transmission lines and other transmission facilities that are owned and operated by third parties. Where we develop our own generator leads, we are exposed to transmission facility development and curtailment risks, which may delay and increase the costs of our projects or reduce the return to us on those investments.

        We often depend on electric transmission lines owned and operated by third parties to deliver the electricity we generate. Some of our projects have limited access to interconnection and transmission capacity because there are many parties seeking access to the limited capacity that is available. We may not be able to secure access to this limited interconnection or transmission capacity at reasonable prices or at all. Moreover, a failure in the operation by third parties of these transmission facilities could result in our losing revenues because such a failure could limit the amount of electricity we deliver. In addition, our production of electricity may be curtailed due to third-party transmission limitations, reducing our revenues and impairing our ability to capitalize fully on a particular project's potential. Such a failure could have a material adverse effect on our business, financial condition and results of operations.

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        In certain circumstances, we have developed and in the future will develop our own generator leads from our projects to available electricity transmission or distribution networks when such facilities do not already exist. In some cases, these facilities may cover significant distances. To construct such facilities, we need approvals, permits and land rights, which may be difficult or impossible to acquire or the acquisition of which may require significant expenditures. We may not be successful in these activities, and our projects that rely on such generator lead development may be delayed, have increased costs or not be feasible. Our failure in operating these generator leads could result in lost revenues because it could limit the amount of electricity we are able to deliver. In addition, we may be required by law or regulation to provide service over our facilities to third parties at regulated rates, which could constrain transmission of our power from the affected facilities, or we could be subject to additional regulatory risks associated with being considered the owner of a transmission line.

We may be unable to construct our wind energy projects on time, and our construction costs could increase to levels that make a project too expensive to complete or make the return on our investment in that project less than expected.

        There may be delays or unexpected developments in completing our wind energy projects, which could cause the construction costs of these projects to exceed our expectations. We may suffer significant construction delays or construction cost increases as a result of a variety of factors, including:

•

failure to receive turbines or other critical components and equipment, including batteries, that meet our design specifications and can be delivered on schedule;



•

failure to complete interconnection to transmission networks;



•

failure to obtain all necessary rights to land access and use;



•

failure to receive quality and timely performance of third-party services;



•

failure to secure and maintain environmental and other permits or approvals;



•

appeals of environmental and other permits or approvals that we obtain;



•

failure to obtain capital to develop our pipeline;



•

shortage of skilled labor;



•

inclement weather conditions;



•

adverse environmental and geological conditions; and



•

force majeure or other events out of our control.

        Any of these factors could give rise to construction delays and construction costs in excess of our expectations. This could prevent us from completing construction of a project, cause defaults under our financing agreements or under PPAs that require completion of project construction by a certain time, cause the project to be unprofitable for us, or otherwise impair our business, financial condition and results of operations.

Demand for wind turbines and related components has exceeded supply in the past and may again in the future. In that case, we may face difficulties in obtaining turbines and related components at affordable prices, in a timely manner or in sufficient quantities.

        A limited number of companies build turbines with a capacity in excess of one MW. In recent years, the rapid growth in aggregate worldwide installed wind power capacity created at times a surge in the demand for wind turbines and their related components. Turbine suppliers have at times had difficulty meeting the demand, leading to significant supply backlogs, increased prices, higher up-front

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payments and deposits and delivery delays. These market conditions may prevail again and if they do, may result in prices that are higher than the costs we expect, less favorable payment terms or may result in insufficient available supplies to sustain our growth. Delays in the delivery of ordered turbines and components could delay the completion of our projects under development. Additionally, future price increases may make it more costly for us to acquire turbines that are not covered by our current turbine supply agreements.

        We may not be able to purchase a sufficient quantity of turbines and related components to satisfy our business plans. Also, turbine and other component manufacturers may give priority to other market participants, including our competitors. To the extent that a wind turbine manufacturer becomes unable or unwilling to supply us with the turbines that we need to develop, construct and operate our projects in accordance with our development plan and budget, we may be unable to find suitable replacements. If we are unable to acquire turbines to meet our development plan, it would have a material adverse effect on our business, financial condition and results of operations.

Warranties from suppliers of turbines, which protect us against turbine non-performance, may be limited by the ability of the vendor to satisfy its obligations under the warranty. In addition, the warranties have time limits and if we are not ready for turbine installation at the time we receive a turbine, that warranty protection can be lost.

        When we purchase turbines, we also enter into warranty agreements with the manufacturer. However, there can be no assurance that the supplier will be able to fulfill its contractual obligations. In addition, these warranties generally expire within two to five years after the turbine delivery date or the date the turbine is commissioned. We may lose all or a portion of the benefit of a warranty if we take delivery of a turbine before we are able to deploy it, as we have in the past. If we seek warranty protection and the vendor is unable or unwilling to perform its obligations under the warranty, whether as a result of the vendor's financial condition or otherwise, or if the term of the warranty has expired, we may suffer reduced warranty availability for the affected turbines, which could have a material adverse effect on our business, financial condition and results of operations. Also, under such warranties, the warranty payments by the manufacturer are typically subject to an aggregate maximum cap that is a portion of the total purchase price of the turbines. Losses in excess of these caps may be our responsibility.

Our use and enjoyment of real property rights for our wind energy projects may be adversely affected by the rights of lienholders and leaseholders that are superior to those of the grantors of those real property rights to us.

        Our wind energy projects generally are and are likely to be located on land we occupy pursuant to long-term easements and leases. The ownership interests in the land subject to these easements and leases may be subject to mortgages securing loans or other liens (such as tax liens) and other easement and lease rights of third parties (such as leases of oil or mineral rights) that were created prior to our easements and leases. As a result, our rights under these easements or leases may be subject, and subordinate, to the rights of those third parties. We perform title searches and obtain title insurance to protect ourselves against these risks. Such measures may, however, be inadequate to protect us against all risk of loss of our rights to use the land on which our projects are located, which could have a material adverse effect on our business, financial condition and results of operations.

Many of our operating projects are, and other future projects may be, subject to regulation by the Federal Energy Regulatory Commission under the Federal Power Act or other regulations that regulate the sale of electricity, which may adversely affect our business.

        Some of our current operating projects are "Qualifying Facilities" that are exempt from regulation as public utilities by the Federal Energy Regulatory Commission (FERC) under the Federal Power Act

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(FPA). Many of our operating projects are, however, subject to rate regulation by FERC under the FPA, and certain of our under-construction and development projects may be subject to such rate regulation in the future. Our projects that are subject to rate regulation are required to obtain FERC acceptance of their rate schedules for wholesale sales of energy, capacity and ancillary services. FERC may revoke or revise an entity's authorization to make wholesale sales at market-based rates if FERC subsequently determines that such entity can exercise market power in transmission or generation, create barriers to entry or engage in abusive affiliate transactions or market manipulation. In addition, public utilities are subject to FERC reporting requirements that impose administrative burdens and that, if violated, can expose the company to civil penalties or other risks.

        Any market-based rate authority that we have or will obtain will be subject to certain market behavior rules. If we are deemed to have violated these rules, we will be subject to potential disgorgement of profits associated with the violation and/or suspension or revocation of our market-based rate authority, as well as potential criminal and civil penalties. If we were to lose market-based rate authority for a project, we would be required to obtain FERC's acceptance of a cost-based rate schedule and could become subject to, among other things, the burdensome accounting, record keeping and reporting requirements that are imposed on public utilities with cost-based rate schedules. This could have an adverse effect on the rates we charge for power from our projects and our cost of regulatory compliance.

        Although the sale of electric energy has been to some extent deregulated, the industry is subject to increasing regulation and even possible re-regulation. Due to major regulatory restructuring initiatives at the federal and state levels, the U.S. electric industry has undergone substantial changes over the past several years. We cannot predict the future design of wholesale power markets or the ultimate effect ongoing regulatory changes will have on our business. Other proposals to re-regulate may be made and legislative or other attention to the electric power market restructuring process may delay or reverse the movement towards competitive markets. If deregulation of the electric power markets is reversed, discontinued or delayed, our business, financial condition and results of operations could be adversely affected.

Current or future litigation or administrative proceedings could have a material adverse effect on our business, financial condition and results of operations.

        We have been and continue to be involved in legal proceedings, administrative proceedings, claims and other litigation that arise in the ordinary course of business. Individuals and interest groups may sue to challenge the issuance of a permit for a wind energy project or seek to enjoin construction of a wind energy project. For example, proceedings have been instituted against us challenging the issuance of some of our permits. Unfavorable outcomes or developments relating to these proceedings, such as judgments for monetary damages, injunctions or denial or revocation of permits, could have a material adverse effect on our business, financial condition and results of operations. In addition, settlement of claims could adversely affect our financial condition and results of operations. See "Business—Legal Proceedings."

Acquisition of existing wind energy assets involves numerous risks.

        We may acquire existing wind energy assets, which involves numerous risks, including: difficulty in developing the assets into operating projects; unanticipated costs and exposure to liabilities; difficulty in integrating the acquired assets; and, if the assets are in new markets, the risks of entering markets where we have limited experience. A failure to achieve the financial returns we expect when we acquire wind energy assets could have an adverse effect on our business.

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We are not able to insure against all potential risks and may become subject to higher insurance premiums.

        Our business is exposed to the risks inherent in the construction and operation of wind energy projects, such as breakdowns, manufacturing defects, natural disasters, terrorist attacks and sabotage. We are also exposed to environmental risks. We have insurance policies covering certain risks associated with our business. Our insurance policies do not, however, cover losses as a result of force majeure, natural disasters, terrorist attacks or sabotage, among other things. We generally do not maintain insurance for certain environmental risks, such as environmental contamination. In addition, our insurance policies are subject to annual review by our insurers and may not be renewed at all or on similar or favorable terms. A serious uninsured loss or a loss significantly exceeding the limits of our insurance policies could have a material adverse effect on our business, financial condition and results of operations.

The loss of one or more members of our senior management or key employees may adversely affect our ability to implement our strategy.

        We depend on our experienced management team and the loss of one or more key executives could have a negative impact on our business. We also depend on our ability to retain and motivate key employees and attract qualified new employees. Because the wind industry is relatively new, there is a scarcity of top-quality employees with experience in the wind industry. If we lose a member of the management team or a key employee, we may not be able to replace him or her. Integrating new employees into our management team and training new employees with no prior experience in the wind industry could prove disruptive to our operations, require a disproportionate amount of resources and management attention and ultimately prove unsuccessful. An inability to attract and retain sufficient technical and managerial personnel could limit or delay our development efforts, which could have a material adverse effect on our business, financial condition and results of operations.

Risks Related to Our Financial Activities

We may not be able to finance the growth of our business, including the development and construction of our wind energy projects and the growth of our organization.

        We are in a capital intensive business and rely heavily on the debt and equity markets to finance the development and construction costs of our projects and other projected capital expenditures. Completion of our projects requires significant capital expenditures and construction costs. Recovery of the capital investment in a wind energy project generally occurs over a long period of time. As a result, we must obtain funds from equity or debt financings, including tax equity transactions, or from government grants to develop and construct our existing project pipeline, to finance the acquisition of turbines, to identify and develop new projects, and to pay the general and administrative costs of operating our business. The cost of turbines represents approximately 70% of the total cost of an average wind energy project. The significant disruption in credit and capital markets generally over 2008 and 2009 has made it difficult to obtain financing on acceptable terms or, in some cases, at all. If we are unable to raise additional funds when needed, we could delay development and construction of projects, reduce the scope of projects or abandon or sell some or all of our development projects, or default on our contractual commitments to buy turbines in the future, any of which would adversely affect our business, financial condition and results of operations.

Our substantial amount of indebtedness maturing in less than one year may adversely affect our ability to operate our business, remain in compliance with debt covenants and make payments on our indebtedness.

        As of September 30, 2009, we had gross outstanding indebtedness of approximately $879.7 million, which represented approximately            % of our total debt and equity capitalization of

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$             million (after giving effect to this offering and giving effect to the pro forma as adjusted assumptions set forth under "Capitalization"), including:

•

$267.3 million of debt under turbine supply loans;



•

$181.2 million of project term debt; and



•

$431.2 million of other debt used to fund development, construction and general and administrative expenses.

        Of this amount, $264.2 million matures prior to December 31, 2010 (after giving effect to amounts repaid or refinanced from October 1, 2009 through December 31, 2009). This amount is principally composed of $240.9 million of turbine supply loan debt due on June 30, 2010. We do not have available cash or short-term liquid investments sufficient to repay all of this indebtedness and we have not obtained commitments for refinancing all of this debt. Therefore, we may not be able to extend the maturity of this indebtedness or to otherwise successfully refinance current maturities.

        The initial report of our independent registered public accounting firm, dated April 30, 2009, on the consolidated financial statements as of and for the year ended December 31, 2008, contained an explanatory paragraph regarding our ability to continue as a going concern. Since April 30, 2009, we obtained additional funding that removed the substantial doubt about whether we would continue as a going concern through December 31, 2009; however, there may be in the future circumstances that raise substantial doubt about our ability to continue as a going concern. If doubts about our ability to continue as a going concern are raised in the future notwithstanding the additional funding we obtained this year and obtain from this offering, our stock price could drop and our ability to raise additional funds, to obtain credit on commercially reasonable terms or to remain in compliance with covenants that we have in place with current lenders may be adversely affected.

        In addition, the assets of some of our subsidiaries collateralize their indebtedness, and in certain cases the assets of certain subsidiaries collateralize the indebtedness of other subsidiaries. This cross-collateralization means that a default by one subsidiary could trigger adverse consequences for other subsidiaries, including possible defaults under their debt agreements, which could have a material adverse effect on our business, financial condition and results of operations.

        Our substantial indebtedness and its short-term maturities could have important consequences. For example, it could:

•

make it difficult for us to satisfy our obligations with respect to our indebtedness, and failure to comply with these obligations could result in an event of default under those agreements, which could be difficult to cure, or result in our bankruptcy;



•

require us to dedicate an even greater portion of our cash flow to pay principal and interest on our debt, reducing the funds available to us and our ability to borrow to operate and grow our business;



•

limit our flexibility to plan for and react to unexpected opportunities;



•

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



•

place us at a disadvantage compared with competitors with less debt.

        Any of these consequences could materially and adversely affect our business, financial condition and results of operations. If we do not comply with our obligations under our debt instruments, we may be required to refinance all or part of our existing debt, borrow additional amounts or sell securities, which we may not be able to do on favorable terms, or at all. In addition, increases in interest rates and changes in debt covenants may reduce the amounts that we can borrow, reduce our net cash flow

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and increase the equity investment we may be required to make to complete development and construction of our projects. These increases could cause some of our projects to become economically unattractive. If we are unable to obtain additional debt or equity financing, we may have to curtail our development activities or be forced to sell assets, perhaps on unfavorable terms, which could have a material adverse effect on our business, financial condition and results of operations.

If our subsidiaries default on their obligations under their debt instruments, we may need to make payments to lenders to prevent foreclosure on the collateral securing the debt, which would cause us to lose certain of our wind energy projects.

        Our subsidiaries incur various types of debt. Non-recourse debt is repayable solely from the applicable project's revenues and is secured by the project's physical assets, major contracts, cash accounts and, in many cases, our ownership interest in the project subsidiary. Limited recourse debt is debt where we have provided a limited guarantee and recourse debt is debt where we have provided a full guarantee, which means if our subsidiaries default on these obligations, we will be liable directly to those creditors, although in the case of limited recourse debt only to the extent of our limited recourse obligations. To satisfy these obligations, we may be required to use amounts distributed by our other subsidiaries as well as other sources of available cash, reducing the cash available to execute our business plan. In addition, if our subsidiaries default on their obligations under non-recourse financing agreements, we may decide to make payments to prevent the creditors of these subsidiaries from foreclosing on the relevant collateral. Such a foreclosure would result in our losing our ownership interest in the subsidiary or in some or all of its assets. The loss of our ownership interest in one or more of our subsidiaries or some or all of their assets could have a material adverse effect on our business, financial condition and results of operations.

Our hedging activities may not adequately manage our exposure to commodity and financial risk, may result in significant losses or require us to use cash collateral to meet margin requirements, each of which could adversely affect our results of operations and cash flow. Liquidity constraints could impair our ability to execute favorable financial hedges in the future.

        Our ownership and operation of wind energy projects exposes us to volatility in market prices of electricity and RECs.

        In an effort to stabilize our revenue from electricity sales, we evaluate the electricity sale options for each of our development projects, including the appropriateness of entering into a PPA or a financial swap, or both. If we sell our electricity into an independent system operator (ISO) market without a PPA, we may enter into a financial swap to stabilize all or a portion of our estimated revenue stream. Under the terms of our existing financial swaps, we are not obligated to physically deliver or purchase electricity. Instead, we receive payments for specified quantities of electricity based on a fixed price and are obligated to pay our counterparty the market price for the same quantities of electricity. These financial swaps cover quantities of electricity that we estimate we are highly likely to produce. As a result, gains or losses under the financial swaps are designed to be offset by decreases or increases in our revenues from spot sales of electricity in liquid ISO markets. However, the actual amount of electricity we generate from operations may be materially different from our estimates for a variety of reasons, including variable wind conditions and turbine availability. If a project does not generate the volume of electricity covered by the associated swap contract, we could incur significant losses if electricity prices in the market rise substantially above the fixed price provided for in the swap. If a project generates more electricity than is contracted in the swap, the excess production will not be hedged and the revenues we derive will be exposed to market price fluctuations.

        We would also incur financial losses as a result of adverse changes in the mark-to-market values of the financial swaps or if the counterparty fails to make payments. We could also experience a reduction in operating cash flow if we are required to post margin in the form of cash collateral. We often are

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required to post cash collateral and issue letters of credit, which fluctuate based on changes in commodity prices, to backstop our obligations under our hedging arrangements. These actions reduce our available borrowing capacity under the credit facilities under which these letters of credit are issued. We have been and expect in the future to be required to post additional cash collateral or issue additional letters of credit if electricity and oil prices rise. We may be exposed to counterparty credit risk, and may suffer losses, if we enter into hedges with entities that are not creditworthy or we obtain credit support that is inadequate with respect to a counterparty.

        We enter into PPAs when we sell our electricity into non-ISO markets or where we believe it is otherwise advisable. Under a PPA, we contract to sell all or a fixed proportion of the electricity generated by one of our projects, sometimes bundled with RECs and capacity, to a customer, often a utility. We do this to stabilize our revenues from that project. We are exposed to the risk that the customer will fail to perform under a PPA, with the result that we will have to sell our electricity at the market price, which could be disadvantageous in the case of fixed-price PPAs. We also in some instances commit to sell minimum levels of generation. If the project generates less than the committed volumes, we may be required to buy the shortfall of electricity on the open market or make payments of liquidated damages.

        We often seek to sell forward a portion of our RECs to fix the revenues from those attributes and hedge against future declines in prices of RECs. If our projects do not generate the amount of electricity required to earn the RECs sold forward or if for any reason the electricity we generate does not produce RECs for a particular state we may be required to make up the shortfall of RECs through purchases on the open market or make payments of liquidated damages. Further, current market conditions may limit our ability to hedge sufficient volumes of our anticipated RECs, leaving us exposed to the risk of falling prices for RECs. Future prices for RECs are also subject to the risk that regulatory changes will adversely affect prices.

We are subject to credit and performance risk from third parties under service and supply contracts.

        We enter into contracts with vendors to supply equipment, materials and other goods and services for the development, construction and operation of wind projects as well as for other business operations. If vendors do not perform their obligations, we may have to enter into new contracts with other vendors at a higher cost or may have schedule disruptions.

We rely on tax equity financing arrangements to realize the benefits provided by PTCs and accelerated tax depreciation. These arrangements may limit the cash distributions we receive and restrict the manner in which we conduct our business.

        In 2007, we entered into two tax equity financing transactions in which we received an aggregate of $146.3 million from tax equity investors in return for investments in our projects. The tax equity investors are entitled to most of the applicable project's operating cash flow from electricity sales and related hedging activities, and substantially all of the PTCs and taxable income or loss until they achieve their agreed rates of return, which we expect to occur in 10 years.

        As a result, a tax equity financing substantially reduces the cash distributions from the applicable project available to us for other uses, and the period during which the tax equity investors receive most of the cash distributions from electricity sales and related hedging activities may last longer than expected if our wind energy projects perform below our expectations.

        Our ability to enter into tax equity arrangements in the future depends on the extension of the expiration date or renewal of the PTC, without which the market for tax equity financing would likely cease to exist. Moreover, there are a limited number of potential tax equity investors, they have limited funds and wind energy developers compete with other renewable energy developers and others for tax equity financing. In addition, conditions in financial and credit markets generally may result in the

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contraction of available tax equity financing. As the renewable energy industry expands, the cost of tax equity financing may increase and there may not be sufficient tax equity financing available to meet the total demand in any year. If we are unable to enter into tax equity financing agreements with attractive pricing terms or at all, we may not be able to use the tax benefits provided by PTCs and accelerated tax depreciation, which could have a material adverse effect on our business, financial condition and results of operations.

        Our tax equity financing agreements provide our tax equity investors with various approval rights with respect to the applicable project or projects, including approvals of annual budgets, indebtedness, incurrence of liens, sales of assets outside the ordinary course of business and litigation settlements. These approval rights may restrict how we conduct our business.

We have had material weaknesses and significant deficiencies in our internal control over financial reporting. Any material weaknesses or significant deficiencies in our internal controls could result in a material misstatement in our financial statements as well as result in our inability to file periodic reports timely as required by federal securities laws, which could have a material adverse effect on our business and stock price.

        We are required to design, implement and maintain effective controls over financial reporting. A material weakness is a deficiency, or a combination of deficiencies, in internal control over financial reporting such that there is a reasonable possibility that a material misstatement of a company's annual or interim financial statements will not be prevented or detected on a timely basis.

        We have had material weaknesses in our internal control over financial reporting that related to the adequacy of our financial and accounting organization support for our financial accounting and reporting needs, including regarding the financial statements as of and for the nine months ended September 30, 2009. These weaknesses mainly resulted from a lack of sufficient personnel, and contributed to significant deficiencies related to: (1) effective policies and procedures designed to ensure certain costs are capitalized in accordance with generally accepted accounting principles and captured in the appropriate accounting period; (2) an effective process to ensure the completeness of accounts payable and accrued expenses; and (3) an effective review, approval and communications process for journal entries.

        While we are implementing procedures designed to remediate these weaknesses and deficiencies, we cannot be certain that we will not in the future have material weaknesses or significant deficiencies in our internal control over financial reporting, or that we will successfully remediate any that we find. If, in the future, we have weaknesses or deficiencies in our internal controls, that could result in a material misstatement in our annual or interim consolidated financial statements or cause us to fail to meet our obligations to file periodic financial reports with the SEC. We also may not be able conclude on an ongoing basis that we have effective internal control over financial reporting as contemplated by Section 404 of the Sarbanes-Oxley Act of 2002 or our independent registered public accounting firm may issue an adverse opinion on the effectiveness of our internal control over financial reporting. Any of these failures could result in adverse consequences that could materially and adversely affect our business, including potential action by the SEC against us, possible defaults under our debt agreements, stockholder lawsuits, delisting of our stock and general damage to our reputation.

Risks Related to Our Structure

We are a holding company and our only material asset after completion of the reorganization and this offering will be our interest in First Wind Holdings, LLC, and accordingly we are dependent upon distributions from First Wind Holdings, LLC to pay taxes and other expenses.

        We will be a holding company and will have no material assets other than our ownership of Series A Units of First Wind Holdings, LLC. We will have no independent means of generating revenue. First Wind Holdings, LLC will be treated as a partnership for U.S. federal income tax

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purposes and, as such, will not itself be subject to U.S. federal income tax. Instead, its taxable income will generally be allocated to its members, including us, pro rata according to the number of membership units each member owns. Accordingly, we will incur income taxes on our proportionate share of any net taxable income of First Wind Holdings, LLC and also will incur expenses related to our operations. We intend to cause First Wind Holdings, LLC to distribute cash to its members in an amount at least equal to the amount necessary to cover their tax liabilities, if any, with respect to their allocable share of the net income of First Wind Holdings, LLC. To the extent that we need funds to pay our tax or other liabilities or to fund our operations, and First Wind Holdings, LLC is restricted from making distributions to us under applicable agreements, laws or regulations or does not have sufficient cash to make these distributions, we may have to borrow funds to meet these obligations and operate our business and our liquidity and financial condition could be materially adversely affected.

We will be required to pay holders of Series B Units most of the tax benefit of any depreciation or amortization deductions we may claim as a result of the tax basis step up we receive in connection with the reorganization and future exchanges of Series B Units.

        Our reorganization is expected to increase the tax basis in the tangible and intangible assets of First Wind Holdings, LLC. In addition, future exchanges of Series B Units (together with an equal number of shares of our Class B common stock) for shares of our Class A common stock are expected to result in additional increases in that tax basis. These increases in tax basis are expected to reduce the amount of tax that we would otherwise be required to pay in the future. We will be required to pay a portion of the cash savings we actually realize from such increase to holders of the Series B Units, which include our Sponsors and certain members of management pursuant to a tax receivable agreement. See "The Reorganization and Our Holding Company Structure—Tax Receivable Agreement."

        We intend to enter into a tax receivable agreement with certain current members of First Wind Holdings, LLC and any future holder of Series B Units, pursuant to which we will pay them                    % of the amount of the cash savings, if any, in U.S. federal, state and local income tax that we realize (or are deemed to realize in the case of an early termination payment by us, or a change in control, as discussed below) as a result of these increases in tax basis. The actual increase in tax basis, as well as the amount and timing of any payments under the tax receivable agreement, will vary depending upon a number of factors including the timing of exchanges, the price of our Class A common stock at the time of the exchanges, the extent to which such exchanges are taxable, the amount and timing of our income and the tax rates then applicable. We expect that, as a result of the size and increases in our share of the tax basis in the tangible and intangible assets of First Wind Holdings, LLC attributable to our interest therein, the payments that we may be required to make pursuant to the tax receivable agreement likely will be substantial. Assuming that there are no material changes in the relevant tax law, and that we earn sufficient taxable income to realize the full tax benefit of the increased depreciation and amortization of our assets, we expect that future aggregate payments under the tax receivable agreement in respect of our initial purchase of membership units of First Wind Holdings, LLC will be approximately $     million and range from approximately $     million to $     million per year over the next 15 years (or $     million and range from approximately $     million to $     million per year over the next 15 years if the underwriters exercise their over-allotment option in full). A $1.00 increase (decrease) in the assumed initial public offering price of $    per Class A share (the midpoint of the range set forth on the cover of this prospectus) would increase (decrease) the aggregate amount of future payments to holders of Series B Units in respect of the purchase by $     million (or $     million if the underwriters exercise their over-allotment option in full).

        If the IRS successfully challenges the tax basis increases described above, we will not be reimbursed for any payments made under the tax receivable agreement. As a result, in certain

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circumstances, we could be required to make payments under the tax receivable agreement in excess of our cash tax savings.

If we are deemed to be an investment company under the Investment Company Act, our business would be subject to applicable restrictions under that Act, which could make it impracticable for us to continue our business as contemplated.

        We believe our company is not an investment company under the Investment Company Act because we are the managing member of First Wind Holdings, LLC and we are primarily engaged in a non-investment company business. We intend to conduct our operations so that we will not be an investment company. However, if we are deemed an investment company, restrictions imposed by the Investment Company Act, including limitations on our capital structure and our ability to transact with affiliates, and changes in financial reporting and regulatory disclosure requirements as a result of being an investment company, could make it impractical for us to continue operating our business as contemplated.

Risks Related to this Offering and Our Class A Common Stock

We will continue to be controlled by our Sponsors after the completion of this offering, which will limit your ability to influence corporate activities and may adversely affect the market price of our Class A common stock.

        Upon completion of the offering, our Sponsors will own or control outstanding common stock representing, in the aggregate, an approximately                % voting interest in us, or approximately                % if the underwriters exercise their over-allotment option in full. As a result of this ownership, our Sponsors will have effective control over the outcome of votes on all matters requiring approval by our stockholders, including the election of directors, the adoption of amendments to our certificate of incorporation and bylaws and approval of a sale of the company and other significant corporate transactions. Our Sponsors can also take actions that have the effect of delaying or preventing a change in control of us or discouraging others from making tender offers for our shares, which could prevent stockholders from receiving a premium for their shares. These actions may be taken even if other stockholders oppose them. Concurrently with the completion of this offering, our Sponsors will enter into a stockholders' agreement pursuant to which they will vote all of the shares of Class A common stock and Class B common stock held by them together on certain matters submitted to a vote of our common stockholders.

The interests of our Sponsors may conflict with the interests of our other stockholders.

        The interests of our Sponsors, or entities controlled by them, may not coincide with the interests of the holders of our Class A common stock. For example, our Sponsors could cause us to make acquisitions or engage in other transactions that increase the amount of our indebtedness or the number of outstanding shares of Class A common stock or sell revenue-generating assets. Additionally, our Sponsors are in the business of trading securities of, and/or investing in, energy companies, including wind energy producers, and related products, including derivatives, commodities and power, and may, from time to time, compete directly or indirectly with us or prevent us from taking advantage of corporate opportunities. Our Sponsors may also pursue acquisition opportunities that may be complementary to our business, and as a result, those acquisition opportunities may not be available to us.

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Conflicts of interest may arise because some of our directors are representatives of our controlling stockholders.

        Messrs. Aube, Eilers, Martin and Raino, who are representatives of our Sponsors, serve on our board of directors. As discussed above, our Sponsors and entities controlled by them may hold equity interests in entities that directly or indirectly compete with us, and companies in which they currently invest may begin competing with us. As a result of these relationships, when conflicts between the interests of our Sponsors, on the one hand, and the interests of our other stockholders, on the other hand, arise, these directors may not be disinterested. Although our directors and officers have a duty of loyalty to us under Delaware law and our certificate of incorporation, transactions that we enter into in which a director or officer has a conflict of interest are generally permissible so long as (1) the material facts relating to the director's or officer's relationship or interest as to the transaction are disclosed to our board of directors and a majority of our disinterested directors, or a committee consisting solely of disinterested directors, approves the transaction, (2) the material facts relating to the director's or officer's relationship or interest as to the transaction are disclosed to our stockholders and a majority of our disinterested stockholders approves the transaction or (3) the transaction is otherwise fair to us. Under our certificate of incorporation, representatives of our Sponsors are not required to offer to 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 a director of ours.

We have limited the liability of and have agreed to indemnify our Sponsors, their affiliates and their subsidiaries, as well as our directors and officers, which may result in these parties assuming greater risks.

        The liability of our Sponsors, their affiliates and their subsidiaries, as well as of our directors and officers, is limited, and we have agreed to indemnify each of these parties to the fullest extent permitted by law. This may lead such parties to assume greater risks when making investment-related decisions than they otherwise would.

        Under our certificate of incorporation and bylaws, the liability of our directors, officers and employees is limited. Similarly, First Wind Holdings, LLC's amended and restated limited liability company agreement contains provisions limiting its managing member's, members', officers' and their respective affiliates', including our Sponsors', liability to First Wind Holdings, LLC and its unit holders. Because First Wind Holdings, LLC is a limited liability company, the exculpation and indemnification provisions in its amended and restated limited liability company agreement are not subject to the limitations set forth in the Delaware General Corporation Law with respect to the indemnification that may be provided by a Delaware corporation to its directors and officers. In addition, we have contractually agreed to indemnify our directors, officers, and their respective affiliates, including our Sponsors, to the fullest extent permitted by law. These protections may result in the indemnified parties', including our Sponsors, tolerating greater risks when making investment-related decisions than otherwise would be the case, for example when determining whether to use leverage in connection with investments. The indemnification arrangements may also give rise to legal claims for indemnification that are adverse to us and holders of our common stock.

We will be a "controlled company" within the meaning of Nasdaq rules and, as a result, will qualify for, and rely on, applicable exemptions from certain corporate governance requirements.

        After completion of this offering we will be a "controlled company" under Nasdaq rules. Under these rules, a company of which more than 50% of the voting power is held by a group is a "controlled company" and may elect not to comply with certain Nasdaq corporate governance requirements, including (1) the requirement that a majority of the board of directors consist of independent directors, (2) the requirement that the nominating committee be composed entirely of independent directors, (3) the requirement that the compensation committee be composed entirely of independent directors

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and (4) the requirement for an annual performance evaluation of the nominating and corporate governance and compensation committees. We intend to rely on this exemption to the extent it is applicable, and therefore we will not have a majority of independent directors or nominating and compensation committees consisting entirely of independent directors. Accordingly, you will not have the same protections afforded to stockholders of companies that are not deemed "controlled companies."

The market price of our Class A common stock could decline due to the large number of shares of Class A common stock eligible for future sale upon the exchange of Series B Units.

        The market price of our Class A common stock could decline as a result of sales of a large number of shares of our Class A common stock eligible for future sale upon the exchange of Series B Units (together with an equal number of shares of our Class B common stock), or the perception that such sales could occur. These sales, or the possibility that these sales may occur, also may make it more difficult for us to raise additional capital by selling equity securities in the future, at a time and price that we deem appropriate.

        After completion of this offering, approximately                Series B Units of First Wind Holdings, LLC will be outstanding. Subject to certain limitations, each Series B Unit, together with a share of Class B common stock, will be exchangeable for one share of Class A common stock as described under "The Reorganization and Our Holding Company Structure—Amended and Restated Limited Liability Company Agreement of First Wind Holdings, LLC." We will enter into a registration rights agreement with our current investors pursuant to which we will grant such investors registration rights with respect to shares of Class A common stock received upon exchange of Series B Units.

Requirements associated with being a public company will increase our costs significantly, as well as divert significant company resources and management attention.

        Before this offering, we have not been subject to the reporting requirements of the Exchange Act or the other rules and regulations of the SEC or any stock exchange relating to publicly-held companies. We are working with our legal, independent auditing and financial advisors to identify those areas in which changes should be made to our financial and management control systems to manage our growth and fulfill our obligations as a public company. These areas include corporate governance, corporate controls, internal audit, disclosure controls and procedures, financial reporting and accounting systems. We have made, and will continue to make, changes in these and other areas. However, the expenses that will be required in order to prepare adequately for being a public company could be material. Compliance with the various reporting and other requirements applicable to public companies will also require considerable management time and attention.

        In addition, being a public company could make it more difficult or more costly for us to obtain certain types of insurance, including directors' and officers' liability insurance, and we may be forced to accept reduced policy limits and coverage or incur substantially higher costs to obtain the same or similar coverage.

Our certificate of incorporation, bylaws and Delaware law contain provisions that could discourage another company from acquiring us, may prevent attempts by our stockholders to replace or remove our current management and could negatively affect our stock price.

        Some provisions of our certificate of incorporation, bylaws and Delaware law may have the effect of delaying, discouraging or preventing a merger or acquisition that our stockholders may consider favorable, including transactions in which stockholders may receive a premium for their shares. In addition, these provisions may frustrate or prevent any attempts by our stockholders to replace or

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remove our current management by making it more difficult for stockholders to replace or remove our board of directors. Our certificate of incorporation and bylaws:

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authorize the issuance of "blank check" preferred stock that could be issued by our board of directors to thwart a takeover attempt without further stockholder approval;



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prohibit cumulative voting in the election of directors, which would otherwise allow holders of less than a majority of stock to elect some directors; and



•

require super majority (80%) voting to effect amendments to provisions of our certificate of incorporation or bylaws regarding board composition, renouncement of business opportunities and other amendments to our certificate of incorporation or bylaws described above.

        In addition, in our certificate of incorporation, we have elected not to be subject to section 203 of the Delaware General Corporation Law, which would otherwise prohibit transactions with a stockholder who owns 15% or more of our stock. As a result, we may be more susceptible to takeover offers that have not been approved by our board. These provisions could limit the price that investors are willing to pay in the future for shares of our Class A common stock. These provisions may also discourage a potential acquisition proposal or tender offer, even if the acquisition proposal or tender offer is at a premium over the then-current market price for our Class A common stock.

Our Class A common stock has not traded publicly before this offering, and we expect the price of our Class A common stock to fluctuate substantially.

        There has not been a public market for our Class A common stock before this offering. A trading market for our Class A common stock may not develop or be liquid. If you purchase shares of our Class A common stock in this offering, you will pay a price that was not established in the public trading markets. The initial public offering price was determined by negotiations between the underwriters and us. You may not be able to resell your shares above the initial public offering price and may suffer a loss of some or all of your investment.

        Broad market and industry factors may adversely affect the market price of our Class A common stock, regardless of our actual operating performance. Other factors that could cause fluctuations in our stock price may include, among other things, the numerous risks and uncertainties as described under "Risk Factors" and under "Cautionary Statement Regarding Forward-Looking Statements."

Factors over which we have little or no control may cause our operating results to vary widely from period to period, which may cause our stock price to decline.

        Our operating results may fluctuate from period to period depending on several factors, including varying weather conditions; changes in regulated or market electricity prices; electricity demand, which follows broad seasonal demand patterns; changes in market prices for RECs; marking to market of our hedging arrangements and unanticipated development or construction delays. Thus, a period-to-period comparison of our operating results may not reflect long-term trends in our business and may not prove to be a relevant indicator of future earnings. These factors may harm our business, financial condition and results of operations and may cause our stock price to decline.

We currently do not intend to pay dividends on our Class A common stock. As a result, your only opportunity to achieve a return on your investment is if the price of our Class A common stock appreciates.

        We currently do not expect to declare or pay dividends on our Class A common stock. Our debt agreements currently limit our ability to pay dividends on our Class A common stock, and we may also enter into other agreements in the future that prohibit or restrict our ability to declare or pay dividends on our Class A common stock. As a result, your only opportunity to achieve a return on your

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investment will be if the market price of our Class A common stock appreciates and you sell your shares at a profit.

You may experience dilution of your ownership interest due to the future issuance of additional shares of our Class A common stock.

        We are in a capital intensive business and we do not have sufficient funds to finance the growth of our business or the construction costs of our development projects or to support our projected capital expenditures. As a result, we will require additional funds from further equity or debt financings, including tax equity financing transactions or sales of preferred shares or convertible debt to complete the development of new projects and pay the general and administrative costs of our business. We may in the future issue our previously authorized and unissued securities, resulting in the dilution of the ownership interests of purchasers of Class A common stock offered hereby. We are currently authorized to issue                 shares of common stock and                shares of preferred stock with preferences and rights as determined by our board of directors. The potential issuance of such additional shares of common stock or preferred stock or convertible debt may create downward pressure on the trading price of our Class A common stock. We may also issue additional shares of Class A common stock or other securities that are convertible into or exercisable for Class A common stock in future public offerings or private placements for capital raising purposes or for other business purposes, potentially at an offering price or conversion price that is below the offering price for Class A common stock in this offering.

You will suffer immediate and substantial dilution in the book value per share of your Class A common stock as a result of this offering.

        The initial public offering price of our Class A common stock is considerably more than the pro forma net tangible book value per share of our outstanding Class A common stock, as adjusted to reflect completion of this offering. This reduction in the book value of your equity is known as dilution. This dilution occurs in large part because our earlier investors paid substantially less than the initial public offering price when they purchased their shares. Investors purchasing Class A common stock in this offering will incur immediate dilution of $                in pro forma net tangible book value per share of Class A common stock, as adjusted to reflect completion of this offering and giving effect to the pro forma as adjusted assumptions set forth under "Capitalization."

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

        Various statements in this prospectus, including those that express a belief, expectation or intention, as well as those that are not statements of historical fact, are forward-looking statements. The forward-looking statements may include projections and estimates concerning the timing and success of specific projects, revenues, income and capital spending. We generally identify forward-looking statements with the words "believe," "intend," "expect," "seek," "may," "should," "anticipate," "could," "estimate," "plan," "predict," "project" or their negatives, and other similar expressions. All statements we make relating to our estimated and projected earnings, margins, costs, expenditures, cash flows, growth rates and financial results or to our expectations regarding future industry trends are forward-looking statements.

        These forward-looking statements are subject to risks and uncertainties that may change at any time, and, therefore, our actual results may differ materially from those that we expected. The forward-looking statements contained in this prospectus are largely based on our expectations, which reflect many estimates and assumptions made by our management. These estimates and assumptions reflect our best judgment based on currently known market conditions and other factors. Although we believe such estimates and assumptions are reasonable, we caution that it is very difficult to predict the impact of known factors and it is impossible for us to anticipate all factors that could affect our actual results. In addition, management's assumptions about future events may prove to be inaccurate. We caution all readers that the forward-looking statements contained in this prospectus are not guarantees of future performance, and we cannot assure any reader that such statements will prove correct or the forward-looking events and circumstances will occur. Actual results may differ materially from those anticipated or implied in the forward-looking statements due to the numerous risks and uncertainties as described under "Risk Factors" and elsewhere in this prospectus. All forward-looking statements are based upon information available to us on the date of this prospectus. We undertake no obligation to update or revise any forward-looking statements as a result of new information, future events or otherwise, except as otherwise required by law. These cautionary statements qualify all forward-looking statements attributable to us, or persons acting on our behalf. The risks, contingencies and uncertainties associated with our forward-looking statements relate to, among other matters, the following:

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our ability to complete our wind energy projects;



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fluctuations in supply, demand, prices and other conditions for electricity, other commodities and RECs;



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changes in law;



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public response to and changes in the local, state and federal regulatory framework affecting renewable energy projects, including the potential expiration and extension of the PTC, ITC and the related U.S. Treasury grants;



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the ability of our counterparties to satisfy their financial commitments;



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the availability of financing, including tax equity financing, for our wind energy projects;



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our ability to continue as a going concern;



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risks associated with our hedging strategies;



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our substantial short-term and long-term indebtedness;



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competition from other energy developers;



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development constraints, including limited geographic availability for suitable sites, obtaining permits on a timely basis and availability of interconnection;

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•

the limited operating history of and technical issues experienced by one of our key turbine suppliers, Clipper;



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potential environmental liabilities and the cost of compliance with applicable environmental laws and regulations;



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our electrical production projections for our wind energy projects;



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our ability to operate our business efficiently, manage capital expenditures and costs (including general and administrative expenses) effectively and generate cash flow;



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our ability to retain and attract senior management and key employees;



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our ability to keep pace with and take advantage of new technologies;



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weather conditions that may affect our electricity production;



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the effects of litigation, including administrative and other proceedings or investigations relating to our wind energy projects under development and those in operation;



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conditions in energy markets as well as financial markets generally, which will be affected by interest rates, foreign currency fluctuations and general economic conditions;



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strains on our resources due to the expansion of our business;



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non-payment by customers and enforcement of certain contractual provisions;



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the effective life and cost of maintenance of our wind turbines and other equipment; and



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other factors discussed under "Risk Factors."

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MARKET AND INDUSTRY DATA

        This prospectus includes market and industry data that we have developed from independent consultant reports, publicly available information, various industry publications, other published industry sources and our internal data and estimates. Our internal data, estimates and forecasts are based upon information obtained from trade and business organizations and other contacts in the markets in which we operate and our management's understanding of industry conditions.

USE OF PROCEEDS

        We estimate that the net proceeds to us from the sale of Class A common stock in this offering will be approximately $            , based on an offering price of $            per share, the midpoint of the range set forth on the cover of this prospectus, after deducting estimated underwriting discounts and commissions and estimated offering expenses.

        We intend to use approximately $            million of our net proceeds from this offering to fund a portion of our capital expenditures for 2010-2013 and the remainder for general corporate purposes.

        A $1.00 increase or decrease in the assumed initial public offering price of $            would increase or decrease net proceeds to us from this offering by approximately $             million after deducting estimated underwriting discounts and commissions and estimated offering expenses.

DIVIDEND POLICY

        We do not expect to declare or pay any cash or other dividends on our Class A common stock, as we intend to reinvest cash flow generated by operations in our business. Our debt agreements effectively limit our ability to pay dividends on our Class A common stock, and we may also enter into credit agreements or other arrangements in the future that prohibit or restrict our ability to declare or pay dividends on our Class A common stock. Class B common stock will not be entitled to any dividend payments.

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CAPITALIZATION

        The following table sets forth the consolidated capitalization of:

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First Wind Holdings, LLC on an actual basis as of September 30, 2009;



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First Wind Holdings Inc. on a pro forma basis as of September 30, 2009 to give effect to all of the reorganization transactions described in "The Reorganization and Our Holding Company Structure;" and



•

First Wind Holdings Inc. on a pro forma as adjusted basis as of September 30, 2009 to give further effect to our sale of shares of common stock in this offering at an assumed initial public offering price of $            per share, the midpoint of the range set forth on the cover of this prospectus, after deducting estimated underwriting discounts and commissions and estimated offering expenses.

        You should read this table together with the information under "Unaudited Pro Forma Financial Information," "Selected Historical Financial and Operating Data," "Management's Discussion and Analysis of Financial Condition and Results of Operations," "The Reorganization and Our Holding Company Structure," "Description of Capital Stock" and in the consolidated financial statements included elsewhere in this prospectus.

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DILUTION

        At September 30, 2009 after giving effect to the reorganization described under "The Reorganization and Our Holding Company Structure," the net tangible book value per share of our Class A common stock was $            . Net tangible book value per share is determined by dividing our tangible net worth (tangible assets less total liabilities) by the total number of outstanding shares of Class A common stock. After giving effect to the sale of shares in this offering at an assumed offering price of $            per share, the midpoint of the range set forth on the cover of this prospectus, after deducting estimated underwriting discounts and commissions and estimated offering expenses, and assuming all Series B Units that will be outstanding immediately after the reorganization are, together with an equal number of shares of our Class B common stock, exchanged for an equal number of shares of Class A common stock, our net tangible book value at September 30, 2009 would have been approximately $            per share. This represents an immediate dilution of $            per share to new investors purchasing Class A common stock in this offering, resulting from the difference between the offering price and the net tangible book value after this offering. The following table illustrates the per share dilution to new investors purchasing Class A common stock in this offering:

        The following table sets forth at September 30, 2009 after giving effect to the reorganization, the total number of shares of Class A common stock purchased from us, and the total consideration and average price per share paid by existing equity holders and by new investors purchasing Class A common stock in this offering, assuming all Series B Units that will be outstanding immediately after the completion of the reorganization are, together with an equal number of shares of Class B common stock, exchanged for an equal number of shares of Class A common stock, at an assumed initial public offering price of $            per share, the midpoint of the range set forth on the cover of this prospectus.

        If the underwriters' over-allotment option is exercised in full, the number of shares held by existing            stockholders after this offering would decrease to             , or                %, of the total number of shares of Class A common stock outstanding immediately following this offering, and the number of shares held by new investors would increase to                or approximately            % of the total number of shares of Class A common stock outstanding immediately following this offering.

        A $1.00 increase (decrease) in the assumed initial public offering price of $            per share would increase (decrease) total consideration paid by new investors in this offering and by all investors by $             million, and would increase (decrease) the average price per share paid by new investors by $            .

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UNAUDITED PRO FORMA FINANCIAL INFORMATION

        The following unaudited consolidated pro forma statements of operations for the year ended December 31, 2008 and the nine months ended September 30, 2009 and the unaudited pro forma consolidated balance sheet as of September 30, 2009 present our consolidated results of operations and financial position to give pro forma effect to the reorganization transactions described in "The Reorganization and Our Holding Company Structure" and the sale of shares in this offering (excluding shares issuable upon exercise of the underwriters' over-allotment option, if any) and the application of the net proceeds from this offering as if all such transactions had been completed as of January 1, 2008 with respect to the unaudited consolidated pro forma statement of operations and as of September 30, 2009 with respect to the unaudited pro forma consolidated balance sheet data. The unaudited pro forma consolidated financial statements reflect pro forma adjustments that are described in the accompanying notes and are based on available information and certain assumptions we believe are reasonable, but are subject to change. We have made, in our opinion, all adjustments that are necessary to present fairly the pro forma financial data.

        The unaudited pro forma financial data are presented for informational purposes only and should not be considered indicative of actual results of operations that would have been achieved had the reorganization transactions and this offering been consummated on the dates indicated, and do not purport to be indicative of statements of financial condition or results of operations as of any future date or any future period.

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FIRST WIND HOLDINGS INC.
Unaudited Pro Forma Consolidated Balance Sheet
As of September 30, 2009
(in thousands, except share amounts)