S-3ASR

As filed with the Securities and Exchange Commission on April 22, 2014

Registration No. 333-            

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM S-3

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

PLUG POWER INC.

(Exact name of Registrant as specified in its charter)

Delaware	22-3672377
(State or other jurisdiction of incorporation or organization)	(I.R.S. Employer Identification Number)

968 Albany Shaker Road

Latham, New York 12110

(518) 782-7700

(Address, Including Zip Code, and Telephone Number, Including Area Code, of Registrant’s Principal Executive Offices)

Andrew Marsh

President and Chief Executive Officer

Plug Power Inc.

968 Albany-Shaker Road

Latham, New York, 12110

(518) 782-7700

(Name, Address, Including Zip Code, and Telephone Number, Including Area Code, of Agent for Service)

Copies to:

Gerard L. Conway Jr., Esq. General Counsel Plug Power Inc.
968 Albany-Shaker Road
Latham, New York, 12110
(518) 782-7700 Robert P. Whalen, Jr., Esq. Jocelyn M. Arel, Esq.
Goodwin Procter LLP
Exchange Place
Boston, Massachusetts 02109-2881
(617) 570-1000

Approximate date of commencement of proposed sale to the public: From time to time after the effective date of this Registration Statement.

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box.  ¨

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, as amended, or the Securities Act, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box.  x

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

If this Form is a registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box.  x

If this Form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box.  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Securities Exchange Act of 1934, as amended, or the Exchange Act.

Large accelerated filer	¨		Accelerated filer	¨
Non-accelerated filer	x	(Do not check if a smaller reporting company)	Smaller reporting company	¨

CALCULATION OF REGISTRATION FEE

Title of Each Class of Securities To Be Registered	Amount to be Registered(1)(2)	Proposed Maximum Offering Price Per Unit(1)(2)	Proposed Maximum Aggregate Offering Price(1)(2)	Amount of Registration Fee(3)
Common Stock, $0.01 par value per share(4)	—	—	—	—
Preferred Stock, $0.01 par value per share	—	—	—	—
Warrants	—	—	—	—
Units	—	—	—	—
Debt Securities	—	—	—	—
Total(5)	—	—	—	—

(1) An indeterminate number of or aggregate principal amount of the securities of each identified class is being registered as may at various times be issued at indeterminate prices.

(2) Not applicable pursuant to General Instruction II.E of Form S-3 under the Securities Act of 1933.

(3) In accordance with Rules 456(b) and 457(r) under the Securities Act, the registrant is deferring payment of all of the registration fee. Any registration fees will be paid subsequently on a pay-as-you-go basis in accordance with Rule 457(r)

(4) In addition to any securities that may be registered hereunder, we are also registering an indeterminate number of shares of common stock as may be issued upon conversion or exercise of the securities issued directly hereunder. No separate consideration will be received for any shares of common stock so issued upon conversion or exercise.

(5) The securities registered hereunder may be sold separately or in a combination with other securities registered hereby.

PROSPECTUS

PLUG POWER INC.

Common Stock

Preferred Stock

Warrants

Units

Debt Securities

By this prospectus, we may offer and sell from time to time, in one or more offerings, common stock, preferred stock, warrants, debt securities or any combination thereof as described in this prospectus. The warrants may be convertible into or exercisable or exchangeable for common stock or preferred stock, the preferred stock may be convertible into or exchangeable for common stock and the debt securities may be convertible into or exchangeable for common stock or preferred stock. You should carefully read this prospectus, any prospectus supplement and any free writing prospectus, as well as any documents incorporated in any of the foregoing by reference, before you invest in our securities. This prospectus may not be used to sell our securities unless accompanied by a prospectus supplement. The prospectus supplement or any related free writing prospectus may also add to, update, supplement or clarify information contained in this prospectus.

Our common stock is traded on the NASDAQ Capital Market under the symbol “PLUG.”

We may offer and sell our securities to or through one or more agents, underwriters, dealers or other third parties or directly to one or more purchasers on a continuous or delayed basis. If we use any agents, underwriters or dealers to sell our securities, we will name them and describe their compensation in a prospectus supplement. The price to the public of our securities and the net proceeds we expect to receive from the sale of such securities will also be set forth in a prospectus supplement.

INVESTING IN OUR SECURITIES INVOLVES A HIGH DEGREE OF RISK. YOU SHOULD REVIEW CAREFULLY THE RISKS AND UNCERTAINTIES REFERENCED UNDER THE HEADING “RISK FACTORS” ON PAGE 4 OF THIS PROSPECTUS AS WELL AS THOSE CONTAINED IN THE APPLICABLE PROSPECTUS SUPPLEMENT AND ANY RELATED FREE WRITING PROSPECTUS, AND IN THE OTHER DOCUMENTS THAT ARE INCORPORATED BY REFERENCE INTO THIS PROSPECTUS OR THE APPLICABLE PROSPECTUS SUPPLEMENT.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is April 22 , 2014.

TABLE OF CONTENTS

	Page
ABOUT THIS PROSPECTUS		1
WHERE YOU CAN FIND ADDITIONAL INFORMATION		2
INCORPORATION OF CERTAIN INFORMATION BY REFERENCE		2
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS		3
RISK FACTORS		4

	Page
ABOUT THE COMPANY		5
DESCRIPTION OF THE SECURITIES		6
RATIO OF EARNINGS TO FIXED CHARGES		8
USE OF PROCEEDS		9
PLAN OF DISTRIBUTION		10
LEGAL MATTERS		12
EXPERTS		12

We are responsible for the information contained and incorporated by reference in this prospectus, in any accompanying prospectus supplement, and in any related free writing prospectus we prepare or authorize. We have not authorized anyone to give you any other information, and we take no responsibility for any other information that others may give you. If you are in a jurisdiction where offers to sell, or solicitations of offers to purchase, the securities offered by this documentation are unlawful, or if you are a person to whom it is unlawful to direct these types of activities, then the offer presented in this document does not extend to you. The information contained in this document speaks only as of the date of this document, unless the information specifically indicates that another date applies. Our business, financial condition, results of operations and prospectus may have changed since those dates.

ABOUT THIS PROSPECTUS

This prospectus is part of an automatic shelf registration statement that we filed with the Securities and Exchange Commission, or the SEC, as a “well-known seasoned issuer” as defined in Rule 405 under the Securities Act of 1933, as amended, or the Securities Act. Under this shelf registration, we may offer shares of our common stock and preferred stock, various series of warrants to purchase common stock or preferred stock, debt securities or any combination thereof, from time to time in one or more offerings. This prospectus only provides you with a general description of the securities we may offer. Each time we offer a type or series of securities under this prospectus, we will provide a prospectus supplement that will contain more specific information about the specific terms of the offering. We may also authorize one or more free writing prospectuses to be provided to you that may contain material information relating to these offerings. This prospectus may not be used to sell our securities unless accompanied by a prospectus supplement. Each such prospectus supplement and any free writing prospectus that we may authorize to be provided to you may also add, update or change information contained in this prospectus or in documents incorporated by reference into this prospectus. We urge you to carefully read this prospectus, any applicable prospectus supplement and any related free writing prospectus, together with the information incorporated herein by reference as described under the headings “Where You Can Find Additional Information” and “Incorporation of Certain Information by Reference” before you invest in our securities.

You should rely only on the information contained or incorporated by reference in this prospectus, any applicable prospectus supplement and any related free writing prospectus. We have not authorized anyone to provide you with different information in addition to or different from that contained in this prospectus, any applicable prospectus supplement and any related free writing prospectus. No dealer, salesperson or other person is authorized to give any information or to represent anything not contained in this prospectus, any applicable prospectus supplement or any related free writing prospectus that we may authorize to be provided to you. You must not rely on any unauthorized information or representation. This prospectus is an offer to sell only the securities offered hereby, but only under circumstances and in jurisdictions where it is lawful to do so. You should assume that the information in this prospectus, any applicable prospectus supplement or any related free writing prospectus is accurate only as of the date on the front of the document and that any information incorporated by reference is accurate only as of the date of the document incorporated by reference, regardless of the time of delivery of this prospectus, any applicable prospectus supplement or any related free writing prospectus, or any sale of a security.

This prospectus contains summaries of certain provisions contained in some of the documents described herein, but reference is made to the actual documents for complete information. All of the summaries are qualified in their entirety by the actual documents. Copies of some of the documents referred to herein have been filed, will be filed or will be incorporated by reference as exhibits to the registration statement of which this prospectus is a part, and you may obtain copies of those documents as described below under the heading “Where You Can Find Additional Information.”

Unless otherwise mentioned or unless the context requires otherwise, throughout this prospectus, any applicable prospectus supplement and any related free writing prospectus, the words “Plug Power,” “we,” “us,” “our,” the “company” or similar references refer to Plug Power Inc. and its subsidiaries; and the term “securities” refers collectively to our common stock, preferred stock, warrants to purchase common stock or preferred stock, debt securities, or any combination of the foregoing securities.

This prospectus and the information incorporated herein by reference includes trademarks, service marks and trade names owned by us or other companies. All trademarks, service marks and trade names included or incorporated by reference into this prospectus, any applicable prospectus supplement or any related free writing prospectus are the property of their respective owners.

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WHERE YOU CAN FIND ADDITIONAL INFORMATION

This prospectus is part of a registration statement that we have filed with the SEC. Certain information in the registration statement has been omitted from this prospectus in accordance with the rules of the SEC. We are a public company and file proxy statements, annual, quarterly and special reports and other information with the SEC. The registration statement, such reports and other information can be inspected and copied at the Public Reference Room of the SEC located at 100 F Street, N.E., Washington D.C. 20549. Copies of such materials, including copies of all or any portion of the registration statement, can be obtained from the Public Reference Room of the SEC at prescribed rates. You can call the SEC at 1-800-SEC-0330 to obtain information on the operation of the Public Reference Room. Such materials may also be accessed electronically by means of the SEC’s home page  on the Internet (www.sec.gov).

INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

The SEC allows us to “incorporate by reference” the information we file with it, which means that we can disclose important information to you by referring you to those documents instead of having to repeat the information in this prospectus. The information incorporated by reference is considered to be part of this prospectus, and later information that we file with the SEC will automatically update and supersede this information. We incorporate by reference the documents listed below that we have filed with the SEC:

• our Annual Report on Form 10-K for the year ended December 31, 2013, filed on March 31, 2014 and as amended by our Annual Report on Form 10-K/A for the year ended December 31, 2013, filed on April 22, 2014;

• our Current Reports on Form 8-K filed on January 10, 2014, January 15, 2014 (excluding Item 7.01), March 6, 2014 and April 3, 2014;

• the section entitled “Description of Registrant’s Securities to be Registered” contained in our Registration Statement on Form 8-A, filed pursuant to Section 12(b) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) on June 24, 2009, as amended by Amendment No. 1 to Form 8-A filed by the Company with the SEC on May 6, 2011, Amendment No. 2 to Form 8-A filed by the Company with the SEC on March 19, 2012, Amendment No. 3 to Form 8-A filed by the Company with the SEC on March 26, 2012, Amendment No. 4 to Form 8-A filed by the Company with the SEC on February 13, 2013 and Amendment No. 5 to Form 8-A filed by the Company with the SEC on May 20, 2013.

We also incorporate by reference into this prospectus all documents we file with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act after the date of this prospectus and prior to the termination of this offering, except any further report or other document or portion thereof that is not deemed filed under such provisions.

You may access our Annual Report on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and amendments to any of these reports, free of charge on the SEC’s website. You may also access the documents incorporated by reference on our website at www.plugpower.com. The information contained in, or that can be accessed through, our website is not part of this prospectus.

In addition, we will furnish without charge to each person, including any beneficial owner, to whom a prospectus is delivered, on written or oral request of such person, a copy of any or all of the documents incorporated by reference in this prospectus (not including exhibits to such documents, unless such exhibits are specifically incorporated by reference in this prospectus or into such documents). Such requests may be directed to Corporate Secretary, Plug Power Inc., 968 Albany-Shaker Road, Latham, New York, 12110, or call (518) 782-7700.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus contains statements that are not historical facts and are considered forward-looking within the meaning of Section 27A of the Securities Act and Section 21E of the Exchange Act. These forward-looking statements contain projections of our future results of operations or of our financial position or state other forward-looking information. In some cases you can identify these statements by forward-looking words such as “anticipate,” “believe,” “could,” “continue,” “estimate,” “expect,” “intend,” “may,” “should,” “will,” “would,” “plan,” “projected” or the negative of such words or other similar words or phrases. We believe that it is important to communicate our future expectations to our investors. However, there may be events in the future that we are not able to accurately predict or control and that may cause our actual results to differ materially from the expectations we describe in our forward-looking statements. Investors are cautioned not to unduly rely on forward-looking statements because they involve risks and uncertainties, and actual results may differ materially from those discussed as a result of various factors, including, but not limited to: the risk that we continue to incur losses and might never achieve or maintain profitability; the risk that we will need to raise additional capital to fund our operations and such capital may not be available to us; our lack of extensive experience in manufacturing and marketing products may impact our ability to manufacture and market products on a profitable and large-scale commercial basis; the risk that unit orders will not ship, be installed and/or converted to revenue, in whole or in part; the risk that pending orders may not convert to purchase orders, in whole or in part; the risk that a loss of one or more of our major customers could result in a material adverse effect on our financial condition; the risk that a sale of a significant number of shares of stock could depress the market price of our common stock; the risk that negative publicity related to our business or stock could result in a negative impact on our stock value and profitability; the risk of potential losses related to any product liability claims and contract disputes; the risk of loss related to an inability to maintain an effective system of internal controls or key personnel; risks related to the use of flammable fuels in our products; the cost and timing of developing, marketing and selling our products and our ability to raise the necessary capital to fund such costs; the ability to achieve the forecasted gross margin on the sale of our products; the risk that our actual net cash used for operating expenses may exceed the projected net cash for operating expenses; the cost and availability of fuel and fueling infrastructures for our products; market acceptance of our products, including GenDrive systems; the volatility of our stock price; our ability to establish and maintain relationships with third parties with respect to product development, manufacturing, distribution and servicing and the supply of key product components; the cost and availability of components and parts for our products; our ability to develop commercially viable products; our ability to reduce product and manufacturing costs; our ability to successfully expand our product lines; our ability to successfully expand internationally; our ability to improve system reliability for our GenDrive systems; competitive factors, such as price competition and competition from other traditional and alternative energy companies; our ability to protect our intellectual property; the cost of complying with current and future federal, state and international governmental regulations; risks associated with potential future acquisitions; and other risks and uncertainties referenced under “Risk Factors” below and in any applicable prospectus supplement or free writing prospectus and any documents incorporated by reference herein or therein. Readers should not place undue reliance on our forward-looking statements. These forward-looking statements speak only as of the date on which the statements were made and are not guarantees of future performance. Except as may be required by applicable law, we do not undertake or intend to update any forward-looking statements after the date of this prospectus or the respective dates of documents incorporated by reference herein or therein that include forward-looking statements.

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RISK FACTORS

Investing in our securities involves a high degree of risk. Before purchasing our securities, you should carefully consider the risks and uncertainties set forth under the heading “Risk Factors” in our Annual Report on Form 10-K for the fiscal year ended December 31, 2013, filed with the SEC on March 31, 2014, which is incorporated by reference in this prospectus, as well as any updates thereto contained in subsequent filings with the SEC or any applicable prospectus supplement or free writing prospectus. If any of these risks were to occur, our business, financial condition or results of operations would likely suffer. In that event, the value of our securities could decline, and you could lose all or part of your investment. The risks and uncertainties we describe are not the only ones facing us. Additional risks not presently known to us or that we currently deem immaterial may also impair our business operations.

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ABOUT THE COMPANY

Plug Power a leading provider of alternative energy technology focused on the design, development, commercialization and manufacture of fuel cell systems for the industrial off-road (forklift or material handling) market.

We are focused on proton exchange membrane, or PEM, fuel cell and fuel processing technologies and fuel cell/battery hybrid technologies, from which multiple products are available. A fuel cell is an electrochemical device that combines hydrogen and oxygen to produce electricity and heat without combustion. Hydrogen is derived from hydrocarbon fuels such as liquid petroleum gas, or LPG, natural gas, propane, methanol, ethanol, gasoline or biofuels. Hydrogen can also be obtained from the electrolysis of water. Hydrogen can be purchased directly from industrial gas providers or can be produced on-site at consumer locations.

We sell and continue to develop fuel cell product solutions to replace lead-acid batteries in material handling vehicles and industrial trucks for some of North America’s largest distribution and manufacturing businesses. We are focusing our efforts on material handling applications (forklifts) at multi-shift high volume manufacturing and high throughput distribution sites where our products and services provide a unique combination of productivity, flexibility and environmental benefits. Our current product line includes: GenDrive, a hydrogen fueled PEM fuel cell system providing power to material handling vehicles; GenKey, our turn-key solution offering complete simplicity to customers transitioning their material handling vehicles to fuel cell power; GenFuel, our hydrogen fueling delivery system; and GenCare, our ongoing maintenance program for both GenDrive fuel cells and GenFuel products.

We sell our products worldwide, with a primary focus on North America, through our direct product sales force, leveraging relationships with original equipment manufacturers, or OEMs, and their dealer networks. We are party to a joint venture based in France with Axane, S.A. under the name Hypulsion, to develop and sell hydrogen fuel cell systems for the European material handling market. We sell to businesses, government agencies and commercial consumers.

We were organized in the State of Delaware on June 27, 1997.

Our principal executive offices are located at 968 Albany-Shaker Road, Latham, New York, 12110, and our telephone number is (518) 782-7700. Our corporate website address is www.plugpower.com. The information on our website is not deemed to be part of this prospectus or any applicable prospectus supplement. Our common stock trades on NASDAQ Capital Market under the symbol “PLUG.”

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DESCRIPTION OF SECURITIES

We may offer shares of our common stock and preferred stock, various series of warrants to purchase common stock or preferred stock, debt securities, in one or more series, as either senior or subordinated debt or as senior or subordinated convertible debt, or any combination thereof from time to time in one or more offerings under this prospectus at prices and on terms to be determined at the time of any offering. This prospectus provides you with a general description of the securities we may offer. Each time we offer a type or series of securities under this prospectus, we will provide a prospectus supplement and/or free writing prospectus that will describe the specific amounts, prices and other important terms of the securities.

Common Stock. We may issue shares of our common stock from time to time. Holders of shares of our common stock are entitled to one vote for each share held of record on all matters to be voted on by stockholders and do not have cumulative voting rights. Subject to the preferences that may be applicable to any then outstanding preferred stock, the holders of our outstanding shares of common stock are entitled to receive dividends, if any, as may be declared from time to time by our board of directors out of legally available funds. In the event of our liquidation, dissolution or winding up, holders of our common stock will be entitled to share ratably in the net assets legally available for distribution to stockholders after the payment of all of our debts and other liabilities, subject to the satisfaction of any liquidation preference granted to the holders of any outstanding shares of preferred stock.

Preferred Stock. We may issue shares of our preferred stock from time to time, in one or more series. Our board of directors will determine the rights, preferences and privileges of the shares of each wholly unissued series, and any qualifications, limitations or restrictions thereon, including dividend rights, conversion rights, preemptive rights, terms of redemption or repurchase, liquidation preferences, sinking fund terms and the number of shares constituting any series or the designation of any series. Convertible preferred stock will be convertible into our common stock or exchangeable for other securities. Conversion may be mandatory or at your option and would be at prescribed conversion rates.

If we sell any series of preferred stock under this prospectus, we will fix the rights, preferences and privileges of the preferred stock of such series, as well as any qualifications, limitations or restrictions thereon, in the certificate of designation relating to that series. We will file as an exhibit to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of any certificate of designation that describes the terms of the series of preferred stock we are offering before the issuance of that series of preferred stock. We urge you to read the applicable prospectus supplement and any free writing prospectus that we may authorize to be provided to you related to the series of preferred stock being offered, as well as the complete certificate of designation that contains the terms of the applicable series of preferred stock.

Warrants. We may issue warrants for the purchase of common stock and/or preferred stock in one or more series. We may issue warrants independently or together with common stock and/or preferred stock, and the warrants may be attached to or separate from these securities. We urge you to read the applicable prospectus supplement and any free writing prospectus that we may authorize to be provided to you related to the particular series of warrants being offered, as well as the complete warrant agreements and warrant certificates that contain the terms of the warrants. Forms of the warrant agreements and forms of warrant certificates containing the terms of the warrants being offered will be filed as exhibits to the registration statement of which this prospectus is a part or will be incorporated by reference from reports that we file with the SEC.

We will evidence each series of warrants by warrant certificates that we will issue. Warrants may be issued under an applicable warrant agreement that we enter into with a warrant agent. We will indicate the name and address of the warrant agent, if applicable, in the prospectus supplement relating to the particular series of warrants being offered.

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Units. We may issue, in one or more series, units consisting of common stock, preferred stock, and/or warrants for the purchase of common stock and/or preferred stock in any combination. We urge you to read the applicable prospectus supplement and any free writing prospectus that we may authorize to be provided to you related to the series of units being offered, as well as the complete unit agreement that contains the terms of the units. We will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of unit agreement and any supplemental agreements that describe the terms of the series of units we are offering before the issuance of the related series of units.

We will evidence each series of units by unit certificates that we will issue. Units may be issued under a unit agreement that we enter into with a unit agent. We will indicate the name and address of the unit agent, if applicable, in the prospectus supplement relating to the particular series of units being offered.

Debt Securities. We may issue debt securities, in one or more series, as either senior or subordinated debt or as senior or subordinated convertible debt. In this prospectus, we have summarized certain general features of the debt securities. We urge you, however, to read the applicable prospectus supplement and any free writing prospectus that we may authorize to be provided to you related to the particular series of debt securities being offered, as well as the complete indenture that contains the terms of the debt securities. We will file as exhibits to the registration statement of which this prospectus is a part, the form of indenture and any supplemental agreements that describe the terms of the series of debt securities we are offering before the issuance of the related series of debt securities.

We may evidence each series of debt securities we will issue by an indenture that we enter into with a trustee. We will indicate the name and address of the trustee, if applicable, in the prospectus supplement relating to the particular series of debt securities being offered.

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RATIO OF EARNINGS TO FIXED CHARGES

Our ratio of earnings to fixed charges for each of the five most recently completed fiscal years and any required interim periods will be specified in a prospectus supplement or in a document that we file with the SEC and incorporate by reference in the future.

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USE OF PROCEEDS

Except as described in any prospectus supplement or in any related free writing prospectus that we may authorize to be provided to you, the net proceeds received by us from our sale of the securities described in this prospectus will be added to our general funds and will be used for our general corporate purposes. From time to time, we may engage in additional public or private financings of a character and amount which we may deem appropriate.

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PLAN OF DISTRIBUTION

We may sell our securities from time to time in one or more transactions. We may sell our securities to or through agents, underwriters, dealers, remarketing firms or other third parties or directly to one or more purchasers or through a combination of any of these methods. In some cases, we or dealers acting with us or on behalf of us may also purchase our securities and reoffer them to the public. We may also offer and sell, or agree to deliver, our securities pursuant to, or in connection with, any option agreement or other contractual arrangement.

Agents whom we designate may solicit offers to purchase our securities.

• We will name any agent involved in offering or selling our securities, and disclose any commissions that we will pay to the agent, in the applicable prospectus supplement.

• Unless we indicate otherwise in the applicable prospectus supplement, agents will act on a best efforts basis for the period of their appointment.

• Agents may be deemed to be underwriters under the Securities Act, of any of our securities that they offer or sell

We may use an underwriter or underwriters in the offer or sale of our securities.

• If we use an underwriter or underwriters, we will execute an underwriting agreement with the underwriter or underwriters at the time that we reach an agreement for the sale of our securities.

• We will include the names of the specific managing underwriter or underwriters, as well as the names of any other underwriters, and the terms of the transactions, including the compensation the underwriters and dealers will receive, in the applicable prospectus supplement.

• The underwriters will use the applicable prospectus supplement, together with the prospectus, to sell our securities.

We may use a dealer to sell our securities.

• If we use a dealer, we will sell our securities to the dealer, as principal.

• The dealer will then sell our securities to the public at varying prices that the dealer will determine at the time it sells our securities.

• We will include the name of the dealer and the terms of the transactions with the dealer in the applicable prospectus supplement.

We may solicit directly offers to purchase our securities, and we may directly sell our securities to institutional or other investors. We will describe the terms of direct sales in the applicable prospectus supplement.

We may engage in at the market offerings into an existing trading market in accordance with Rule 415(a)(4) of the Securities Act.

We will indemnify agents, underwriters and dealers against certain liabilities, including liabilities under the Securities Act. Agents, underwriters and dealers, or their affiliates, may be customers of, engage in transactions with or perform services for us or our respective affiliates, in the ordinary course of business.

We may authorize agents and underwriters to solicit offers by certain institutions to purchase our securities at the public offering price under delayed delivery contracts.

• If we use delayed delivery contracts, we will disclose that we are using them in the prospectus supplement and will tell you when we will demand payment and when delivery of our securities will be made under the delayed delivery contracts.

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• These delayed delivery contracts will be subject only to the conditions that we describe in the prospectus supplement.

• We will describe in the applicable prospectus supplement the commission that underwriters and agents soliciting purchases of our securities under delayed delivery contracts will be entitled to receive.

Unless otherwise specified in connection with a particular underwritten offering of our securities, the underwriters will not be obligated to purchase offered securities unless specified conditions are satisfied, and if the underwriters do purchase any offered securities, they will purchase all offered securities.

In connection with underwritten offerings of the offered securities and in accordance with applicable law and industry practice, the underwriters in certain circumstances are permitted to engage in certain transactions that stabilize the price of our securities. Such transactions consist of bids or purchases for the purpose of pegging, fixing or maintaining the price of our securities. If the underwriters create a short position in our securities in connection with the offering (i.e., if they sell more securities than are set forth on the cover page of the applicable prospectus supplement), the underwriters may reduce that short position by purchasing our securities in the open market or as otherwise provided in the applicable prospectus supplement. The underwriters may also impose a penalty bid, whereby selling concessions allowed to dealers participating in the offering may be reclaimed if the securities sold by them are repurchased in connection with stabilization transactions. In general, purchases of a security for the purpose of stabilization or to reduce a short position could cause the price of the security to be higher than it might be in the absence of such purchases. The imposition of a penalty bid might also have an effect on the price of our securities to the extent that it were to discourage resales of our securities. The underwriters are not required to engage in these activities and may end any of these activities at any time.

We may effect sales of securities in connection with forward sale, option or other types of agreements with third parties. Any distribution of securities pursuant to any forward sale agreement may be effected from time to time in one or more transactions that may take place through a stock exchange, including block trades or ordinary broker’s transactions, or through broker-dealers acting either as principal or agent, or through privately-negotiated transactions, or through an underwritten public offering, or through a combination of any such methods of ale, at market prices prevailing at the time of sale, prices relating to such prevailing market prices or at negotiated or fixed prices.

The specific terms of the lock-up provisions, if any, in respect of any given offering will be described in the applicable prospectus supplement.

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LEGAL MATTERS

The validity of the securities being offered by this prospectus will be passed upon by Goodwin Procter LLP, Boston, Massachusetts.

EXPERTS

The consolidated financial statements of Plug Power Inc. and subsidiaries as of December 31, 2013 and 2012, and for each of the years in the three-year period ended December 31, 2013 have been incorporated by reference herein and in the Registration Statement in reliance upon the report of KPMG LLP, independent registered public accounting firm, incorporated by reference herein, and upon authority of said firm as experts in accounting and auditing.

12

PART II

INFORMATION NOT REQUIRED IN THE PROSPECTUS

Item 14. Other Expenses of Issuance and Distribution.

The following table sets forth the estimated costs and expenses, other than underwriting discounts and commissions, in connection with the issuance and distribution of the securities registered hereby. The registrant is deferring payment of the registration fee in reliance on Rule 456(b) and Rule 457(r) under the Securities Act. All the amounts shown are estimates.

	Amount to be Paid
SEC registration fee	$	(1)
NASDAQ Capital Market listing fee		(2)
Accounting fees and expenses		(2)
Legal fees and expenses		(2)
Trustee and Transfer Agent fees and expenses		(2)
Printing fees		(2)
Miscellaneous		(2)
Total	$	(2)

(1) Omitted because the registration fee is being deferred pursuant to Rule 456(b) and Rule 457(r) under the Securities Act.

(2) These fees and expenses depend on the securities offered and the number of issuances, and accordingly cannot be estimated at this time and will be reflected in the applicable prospectus supplement.

Item 15. Indemnification of Directors and Officers.

In accordance with Section 145 of the Delaware General Corporation Law, Article VII of our amended and restated certificate of incorporation provides that no director of Plug Power shall be personally liable to Plug Power or its stockholders for monetary damages for breach of fiduciary duty as a director, except for liability (1) for any breach of the director’s duty of loyalty to Plug Power or its stockholders, (2) for acts or omissions not in good faith or which involve intentional misconduct or a knowing violation of law, (3) in respect of unlawful dividend payments or stock redemptions or repurchases, or (4) for any transaction from which the director derived an improper personal benefit. In addition, our amended and restated certificate of incorporation provides that if the Delaware General Corporation Law is amended to authorize the further elimination or limitation of the liability of directors, then the liability of a director of the corporation shall be eliminated or limited to the fullest extent permitted by the Delaware General Corporation Law, as so amended.

Article V of our amended and restated by-laws provides for indemnification by Plug Power of its officers and certain non-officer employees under certain circumstances against expenses, including attorneys fees, judgments, fines and amounts paid in settlement, reasonably incurred in connection with the defense or settlement of any threatened, pending or completed legal proceeding in which any such person is involved by reason of the fact that such person is or was an officer or employee of the registrant if such person acted in good faith and in a manner he or she reasonably believed to be in or not opposed to the best interests of Plug Power, and, with respect to criminal actions or proceedings, if such person had no reasonable cause to believe his or her conduct was unlawful.

In addition, we have entered into indemnification agreements with each of our directors. The indemnification agreements require, among other matters, that we indemnify our directors to the fullest extent permitted by law and advance to the director’s all related expenses, subject to reimbursement if it is subsequently determined that indemnification is not permitted. Under these agreements, we must also indemnify and advance all expenses incurred by directors seeking to enforce their rights under the indemnification agreements and may cover directors under directors’ and officers’ liability insurance.

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Item 16. Exhibits.

Exhibit Number	Description of the Document
1.1(1)	Form of Underwriting Agreement.
3.1(2)	Amended and Restated Certificate of Incorporation of Plug Power Inc.
3.2(3)	Third Amended and Restated By-laws of Plug Power Inc.
3.3(2)	Certificate of Amendment to Amended and Restated Certificate of Incorporation of Plug Power Inc.
3.4(4)	Second Certificate of Amendment of Amended and Restated Certificate of Incorporation of Plug Power Inc.
4.1(5)	Certificate of Designations, Preferences and Rights of a Series of Preferred Stock of Plug Power Inc. classifying and designating the Series A Junior Participating Cumulative Preferred Stock.
4.1(6)	Certificate of Designations of Series C Redeemable Convertible Preferred Stock of Plug Power Inc.
4.2(5)	Shareholder Rights Agreement, dated as of June 23, 2009, between Plug Power Inc. as Registrar and American Stock Transfer & Trust Company, LLC, as Rights Agent.
4.3(7)	Amendment No. 1 to Form 8-A effective as of May 6, 2011 by and between Plug Power Inc. and American Stock Transfer & Trust Company, LLC, as Rights Agent.
4.4(8)	Amendment No. 2 to Form 8-A effective as of March 16, 2012 by and between Plug Power Inc. and American Stock Transfer & Trust Company, LLC, as Rights Agent.
4.5(9)	Amendment No. 3 to Form 8-A effective as of March 23, 2012 by and between Plug Power Inc. and Broadridge Corporate Issuer Solutions, Inc., as Rights Agent.
4.6(10)	Amendment No. 4 to Form 8-A effective as of February 12, 2013 by and between Plug Power Inc. and Broadridge Corporate Issuer Solutions, Inc., as Rights Agent.
4.7(11)	Amendment No. 5 to Form 8-A effective as of May 8, 2013 by and between Plug Power Inc. and Broadridge Corporate Issuer Solutions, Inc., as Rights Agent.
4.8(12)	Form of Common Stock Certificate of Plug Power Inc.
4.9(1)	Specimen Preferred Stock Certificate and Form of Certificate of Designation of Preferred Stock.
4.10(1)	Form of Common Stock Warrant Agreement and Warrant Certificate.
4.11(1)	Form of Preferred Stock Warrant Agreement and Warrant Certificate.
4.12(1)	Form of Unit Agreement.
4.13(1)	Form of Indenture.
4.14(1)	Form of Debt Security.
5.1	Opinion of Goodwin Procter LLP.
12.1(1)	Computation of Ratio of Earnings to Fixed Charges.
23.1	Consent of KPMG LLP, Independent Registered Public Accounting Firm.
23.2	Consent of Goodwin Procter LLP (included in Exhibit 5.1).
24.1	Power of Attorney (included on signature page).
25.1(1)	Form T-1—Statement of Eligibility for Indenture under the Trust Indenture Act of 1939.

(1) To be filed, if necessary, subsequent to the effectiveness of this registration statement by incorporation by reference pursuant to a Current Report on Form 8-K in connection with an offering of securities.

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(2) Incorporated herein by reference to the registrant’s Annual Report on Form 10-K for the year ended December 31, 2008 filed with the SEC on March 16, 2009.

(3) Incorporated herein by reference to the registrant’s Current Report on Form 8-K dated October 28, 2009, filed with the SEC on November 2, 2009.

(4) Incorporated herein by reference to the registrant’s Current Report on Form 8-K dated May 19, 2011, filed with the SEC on May 19, 2011.

(5) Incorporated herein by reference to the registrant’s Registration Statement on Form 8-A dated June 24, 2009, filed with the SEC on June 24, 2009.

(6) Incorporated herein by reference to the registrant’s Current Report on Form 8-K dated May 16, 2013, filed with the SEC on May 20, 2013.

(7) Incorporated herein by reference to the registrant’s Current Report on Form 8-K dated May 6, 2011.

(8) Incorporated herein by reference to the registrant’s Current Report on Form 8-K dated March 19, 2012.

(9) Incorporated herein by reference to the registrant’s Current Report on Form 8-K dated March 26, 2012.

(10) Incorporated herein by reference to the registrant’s Current Report on Form 8-K dated February 13, 2013.

(11) Incorporated herein by reference to the registrant’s Current Report on Form 8-K dated May 8, 2013.

(12) Incorporated herein by reference to the registrant’s Registration Statement on Form S-1/A (File Number 333-86089) dated October 1, 1999, filed with the SEC on October 1, 1999.

Item 17. Undertakings.

The undersigned registrant hereby undertakes:

(1) To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

(i) To include any prospectus required by Section 10(a)(3) of the Securities Act;

(ii) To reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement. Notwithstanding the foregoing, any increase or decrease in the volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the Securities and Exchange Commission, or the Commission, pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than a 20% change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement; and

(iii) To include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement;

provided, however, that paragraphs (1)(i), (1)(ii) and (1)(iii) above do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the Commission by the registrant pursuant to Section 13 or Section 15(d) of the Exchange Act that are incorporated by reference in the registration statement, or is contained in a form of prospectus filed pursuant to Rule 424(b) that is part of the registration statement.

(2) That, for the purpose of determining any liability under the Securities Act, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(3) To remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.

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(4) That, for the purpose of determining liability under the Securities Act to any purchaser:

(A) Each prospectus filed by the registrant pursuant to Rule 424(b)(3) shall be deemed to be part of the registration statement as of the date the filed prospectus was deemed part of and included in the registration statement; and

(B) Each prospectus required to be filed pursuant to Rule 424(b)(2), (b)(5), or (b)(7) as part of a registration statement in reliance on Rule 430B relating to an offering made pursuant to Rule 415(a)(1)(i), (vii), or (x) for the purpose of providing the information required by Section 10(a) of the Securities Act shall be deemed to be part of and included in the registration statement as of the earlier of the date such form of prospectus is first used after effectiveness or the date of the first contract of sale of securities in the offering described in the prospectus. As provided in Rule 430B, for liability purposes of the issuer and any person that is at that date an underwriter, such date shall be deemed to be a new effective date of the registration statement relating to the securities in the registration statement to which that prospectus relates, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof. Provided, however , that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such effective date, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such effective date.

(5) That, for the purpose of determining liability of the registrant under the Securities Act to any purchaser in the initial distribution of the securities, the undersigned registrant undertakes that in a primary offering of securities of the undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

(i) Any preliminary prospectus or prospectus of the undersigned registrant relating to the offering required to be filed pursuant to Rule 424;

(ii) Any free writing prospectus relating to the offering prepared by or on behalf of the undersigned registrant or used or referred to by the undersigned registrant;

(iii) The portion of any other free writing prospectus relating to the offering containing material information about the undersigned registrant or its securities provided by or on behalf of the undersigned registrant; and

(iv) Any other communication that is an offer in the offering made by the undersigned registrant to the purchaser.

(6) That, for purposes of determining any liability under the Securities Act, each filing of the registrant’s annual report pursuant to Section 13(a) or 15(d) of the Exchange Act (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Exchange Act) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of the securities at that time shall be deemed to be the initial bona fide offering thereof.

(7) That, for purposes of determining any liability under the Securities Act, the information omitted from the form of prospectus filed as part of this registration statement in reliance upon Rule 430A and contained in a form of prospectus filed by the registrant pursuant to Rule 424(b) (1) or (4) or 497(h) under the Securities Act shall be deemed to be part of this registration statement as of the time it was declared effective.

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(8) That, for the purpose of determining any liability under the Securities Act, each post-effective amendment that contains a form of prospectus shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(9) To file an application for the purpose of determining the eligibility of the trustee to act under subsection (a) of Section 310 of the Trust Indenture Act in accordance with the rules and regulations prescribed by the Commission under Section 305(b)(2) of the Trust Indenture Act.

Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant has been advised that in the opinion of the Commission such indemnification is against public policy as expressed in the Securities Act and is, therefore unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Act and will be governed by the final adjudication of such issue.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Latham, State of New York, on the 22nd day of April, 2014.

PLUG POWER INC.
By:	/s/ Andrew Marsh

Name:	Andrew Marsh
Title:	President and Chief Executive Officer

POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below hereby severally constitutes and appoints Andrew Marsh and Gerard L. Conway, Jr., and each of them, as such person’s true and lawful attorneys in fact and agents, with full power of substitution and resubstitution, for such person and in such persons’s name, place, and stead, in any and all capacities, to sign any and all amendments (including post effective amendments or any abbreviated or subsequent registration statement and any amendments thereto filed pursuant to Rule 462(b) and any supplement to any prospectus included in this registration statement or any such amendment or any abbreviated or subsequent registration statement filed pursuant to Rule 462(b)), and to file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys in fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in connection therewith, as fully to all intents and purposes as such person might or could do in person, hereby ratifying and confirming all that said attorneys in fact and agents, or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1933, as amended, this Registration Statement has been signed by the following persons in the capacities and on the dates indicated.

Signature	Title	Date
/s/  Andrew Marsh Andrew Marsh	President, Chief Executive Officer and Director (Principal Executive Officer)	April 22, 2014
/s/  David P. Waldek David P. Waldek	Interim Chief Financial Officer (Principal Financial Officer)	April 22, 2014
/s/  Jill McCoskey Jill McCoskey	Chief Accounting Officer (Principal Accounting Officer)	April 22, 2014
/s/  George C. McNamee George C. McNamee	Chairman of the Board of Directors	April 22, 2014
/s/  Larry G. Garberding Larry G. Garberding	Director	April 22, 2014
/s/  Gary K. Willis Gary K. Willis	Director	April 22, 2014

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Signature	Title	Date
/s/  Maureen O. Helmer Maureen O. Helmer	Director	April 22, 2014
/s/  Douglas T. Hickey Douglas T. Hickey	Director	April 22, 2014
/s/  Johannes M. Roth Johannes M. Roth	Director	April 22, 2014
/s/  Evgeny Miroshnichenko Evgeny Miroshnichenko	Director	April 22, 2014
/s/  Gregory L. Kenausis Gregory L. Kenausis	Director	April 22, 2014
/s/  Xavier Pontone Xavier Pontone	Director	April 22, 2014

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EXHIBIT INDEX

Exhibit Number	Description of the Document
1.1(1)	Form of Underwriting Agreement.
3.1(2)	Amended and Restated Certificate of Incorporation of Plug Power Inc.
3.2(3)	Third Amended and Restated By-laws of Plug Power Inc.
3.3(2)	Certificate of Amendment to Amended and Restated Certificate of Incorporation of Plug Power Inc.
3.4(4)	Second Certificate of Amendment of Amended and Restated Certificate of Incorporation of Plug Power Inc.
4.1(5)	Certificate of Designations, Preferences and Rights of a Series of Preferred Stock of Plug Power Inc. classifying and designating the Series A Junior Participating Cumulative Preferred Stock.
4.1(6)	Certificate of Designations of Series C Redeemable Convertible Preferred Stock of Plug Power Inc.
4.2(5)	Shareholder Rights Agreement, dated as of June 23, 2009, between Plug Power Inc. as Registrar and American Stock Transfer & Trust Company, LLC, as Rights Agent.
4.3(7)	Amendment No. 1 to Form 8-A effective as of May 6, 2011 by and between Plug Power Inc. and American Stock Transfer & Trust Company, LLC, as Rights Agent.
4.4(8)	Amendment No. 2 to Form 8-A effective as of March 16, 2012 by and between Plug Power Inc. and American Stock Transfer & Trust Company, LLC, as Rights Agent.
4.5(9)	Amendment No. 3 to Form 8-A effective as of March 23, 2012 by and between Plug Power Inc. and Broadridge Corporate Issuer Solutions, Inc., as Rights Agent.
4.6(10)	Amendment No. 4 to Form 8-A effective as of February 12, 2013 by and between Plug Power Inc. and Broadridge Corporate Issuer Solutions, Inc., as Rights Agent.
4.7(11)	Amendment No. 5 to Form 8-A effective as of May 8, 2013 by and between Plug Power Inc. and Broadridge Corporate Issuer Solutions, Inc., as Rights Agent.
4.8(12)	Form of Common Stock Certificate of Plug Power Inc.
4.9(1)	Specimen Preferred Stock Certificate and Form of Certificate of Designation of Preferred Stock.
4.10(1)	Form of Common Stock Warrant Agreement and Warrant Certificate.
4.11(1)	Form of Preferred Stock Warrant Agreement and Warrant Certificate.
4.12(1)	Form of Unit Agreement.
4.13(1)	Form of Indenture.
4.14(1)	Form of Debt Security.
5.1	Opinion of Goodwin Procter LLP.
12.1(1)	Computation of Ratio of Earnings to Fixed Charges.
23.1	Consent of KPMG LLP, Independent Registered Public Accounting Firm.
23.2	Consent of Goodwin Procter LLP (included in Exhibit 5.1).
24.1	Power of Attorney (included on signature page).
25.1(1)	Form T-1 – Statement of Eligibility for Indenture under the Trust Indenture Act of 1939.

(1) To be filed, if necessary, subsequent to the effectiveness of this registration statement by incorporation by reference pursuant to a Current Report on Form 8-K in connection with an offering of securities.

(2) Incorporated herein by reference to the registrant’s Annual Report on Form 10-K for the year ended December 31, 2008 filed with the SEC on March 16, 2009.

(3) Incorporated herein by reference to the registrant’s Current Report on Form 8-K dated October 28, 2009, filed with the SEC on November 2, 2009.

(4) Incorporated herein by reference to the registrant’s Current Report on Form 8-K dated May 19, 2011, filed with the SEC on May 19, 2011.

(5) Incorporated herein by reference to the registrant’s Registration Statement on Form 8-A dated June 24, 2009, filed with the SEC on June 24, 2009.

(6) Incorporated herein by reference to the registrant’s Current Report on Form 8-K dated May 16, 2013, filed with the SEC on May 20, 2013.

(7) Incorporated herein by reference to the registrant’s Current Report on Form 8-K dated May 6, 2011.

(8) Incorporated herein by reference to the registrant’s Current Report on Form 8-K dated March 19, 2012.

(9) Incorporated herein by reference to the registrant’s Current Report on Form 8-K dated March 26, 2012.

(10) Incorporated herein by reference to the registrant’s Current Report on Form 8-K dated February 13, 2013.

(11) Incorporated herein by reference to the registrant’s Current Report on Form 8-K dated May 8, 2013.

(12) Incorporated herein by reference to the registrant’s Registration Statement on Form S-1/A (File Number 333-86089) dated October 1, 1999, filed with the SEC on October 1, 1999.

EX-5.1

Exhibit 5.1

[Letterhead of Goodwin Procter LLP]

April 22, 2014

Plug Power Inc.

968 Albany-Shaker Road

Latham, New York, 12110

Re: Securities Being Registered under Registration Statement on Form S-3

Ladies and Gentlemen:

We have acted as counsel to you in connection with your filing of an automatic shelf registration statement on Form S-3 (as amended or supplemented, the “Registration Statement”) pursuant to the Securities Act of 1933, as amended (the “Securities Act”). Pursuant to the Registration Statement, the Company is registering under the Securities Act an indeterminate amount of (i) common stock, par value $0.01 per share (the “Common Stock”), of Plug Power Inc., a Delaware corporation (the “Company”), (ii) preferred stock, par value $0.01 per share, of the Company (the “Preferred Stock”), (iii) debt securities of the Company (“Debt Securities”), (iv) warrants to purchase Common Stock, Preferred Stock, Debt Securities or Units (as defined below ) (“Warrants”), and (v) units comprised of Common Stock, Preferred Stock, Debt Securities, Stock Purchase Contracts (as defined below), Warrants and other securities in any combination (“Units”). The Common Stock, Preferred Stock, Debt Securities, Warrants and Units are sometimes referred to collectively herein as the “Securities.” Securities may be issued in an unspecified number (with respect to Common Stock, Preferred Stock, Warrants, Units and Stock Purchase Contracts) or in an unspecified principal amount (with respect to Debt Securities). The Registration Statement provides that the Securities may be offered separately or together, in separate series, in amounts, at prices and on terms to be set forth in one or more prospectus supplements (each a “Prospectus Supplement”) to the prospectus contained in the Registration Statement.

We have reviewed such documents and made such examination of law as we have deemed appropriate to give the opinions set forth below. We have relied, without independent verification, on certificates of public officials and, as to matters of fact material to the opinions set forth below, and on certificates of officers of the Company.

The opinions set forth below are limited to the Delaware General Corporation Law (which includes reported judicial decisions interpreting the Delaware General Corporation Law), the law of New York, and the federal law of the United States. Without limiting the generality of the foregoing, we express no opinion with respect to (i) state securities or “blue sky” laws, or (ii) state or federal antitrust laws.

For purposes of the opinions set forth below, without limiting any other exceptions or qualifications set forth herein, we have assumed that after the issuance of any Securities offered pursuant to the Registration Statement, the total number of issued shares of Common Stock or Preferred Stock, as applicable, together with the total number of shares of such stock issuable upon the exercise, exchange, conversion or settlement, as the case may be, of any exercisable, exchangeable or convertible security (including without limitation any Unit or Stock Purchase Contract), as the case may be, then outstanding, will not exceed the total number of authorized shares of Common Stock or Preferred Stock, as applicable, under the Company’s certificate of incorporation as then in effect (the “Charter”).

For purposes of the opinions set forth below, we refer to the following as the “Future Authorization and Issuance” of Securities:

• with respect to any of the Securities, (a) the authorization by the Company of the amount, terms and issuance of such Securities (the “Authorization”) and (b) the issuance of such Securities in accordance with the Authorization therefor upon the receipt by the Company of the consideration (which, in the case of shares of Common Stock or Preferred Stock, is not less than the par value of such shares) to be paid therefor in accordance with the Authorization;

• with respect to Preferred Stock, (a) the establishment of the terms of such Preferred Stock by the Company in conformity with the Charter and applicable law and (b) the execution, acknowledgement and filing with the Delaware Secretary of State, and the effectiveness of, a certificate of designations to the Charter setting forth the terms of such Preferred Stock in accordance with the Charter and applicable law;

• with respect to Debt Securities, (a) the authorization, execution and delivery of the indenture or a supplemental indenture relating to such Securities by the Company and the trustee thereunder and/or (b) the establishment of the terms of such Securities by the Company in conformity with the applicable indenture or supplemental indenture and applicable law, and (c) the execution, authentication and issuance of such Securities in accordance with the applicable indenture or supplemental indenture and applicable law; and

• with respect to Warrants, Units or Stock Purchase Contracts, (a) the authorization, execution and delivery by the Company and the other parties thereto of any agreement under which such Securities are to be issued and (b) the establishment of the terms of such Securities, and the execution and delivery of such Securities, in conformity with any applicable agreement under which such Securities are to be issued and applicable law.

Based upon the foregoing, and subject to the additional qualifications set forth below, we are of the opinion that:

1. Upon the Future Authorization and Issuance of shares of Common Stock, such shares of Common Stock will be validly issued, fully paid and nonassessable.

2. Upon the Future Authorization and Issuance of shares of Preferred Stock, such shares of Preferred Stock will be validly issued, fully paid and nonassessable.

3. Upon the Future Authorization and Issuance of Debt Securities, such Debt Securities will be valid and binding obligations of the Company.

4. Upon the Future Authorization and Issuance of Warrants, such Warrants will be valid and binding obligations of the Company.

5. Upon the Future Authorization and Issuance of Units, such Units will be valid and binding obligations of the Company

The opinions expressed above are subject to bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium and other similar laws of general application affecting the rights and remedies of creditors and to general principles of equity.

This opinion letter and the opinions it contains shall be interpreted in accordance with the Legal Opinion Principles issued by the Committee on Legal Opinions of the American Bar Association’s Business Law Section as published in 53 Business Lawyer 831 (May 1998).

We hereby consent to the inclusion of this opinion as Exhibit 5.1 to the Registration Statement and to the references to our firm under the caption “Legal Matters” in the Registration Statement. In giving our consent, we do not admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations thereunder.

Very truly yours,

/s/ Goodwin Procter LLP

GOODWIN PROCTER LLP

EX-23.1

Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

The Board of Directors

Plug Power Inc.

We consent to the use of our report dated March 31, 2014, with respect to the consolidated balance sheets of Plug Power Inc. and subsidiaries as of December 31, 2013 and 2012, and the related consolidated statements of operations, comprehensive loss, stockholders’ (deficit) equity, and cash flows for each of the years in the three-year period ended December 31, 2013, incorporated by reference in this Registration Statement on Form S-3 of Plug Power, Inc. and to the reference to our firm under the heading “Experts.”

/s/ KPMG LLP

Albany, New York

April 22, 2014