(Amendment No. 5)

Under the Securities Exchange Act of 1934*

(Name of Issuer)

(Title of Class of Securities)

(CUSIP Number)

(Name, Address and Telephone Number of Person
Authorized to Receive Notices and Communications)

(Date of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box o

Note. Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Rule 13d-7(b) for other parties to whom copies are to be sent.

*The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 (the "Act"), or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

(Amendment No. 5)

Statement of

OJSC “Third Generation Company of the Wholesale Electricity Market”

and

JSC “INTER RAO UES”

Pursuant to Section 13(d) of the Securities Exchange Act of 1934
in respect of

Plug Power Inc.

Explanatory Note:  This Amendment No. 5 (this “Amended Statement”) amends and supplements the Statement on Schedule 13D of OJSC “Third Generation Company of the Wholesale Electricity Market” (“OGK-3”) and JSC “INTER RAO UES” (“INTER RAO UES” and collectively with OGK-3, the “Reporting Persons”) regarding the common stock, par value $0.01 per share (the “Common Stock”), of Plug Power Inc., a Delaware corporation (the “Issuer”).  The Issuer’s principal executive offices are located at 968 Albany-Shaker Road, Latham, New York 12110. Pursuant to Rule 13d-1(k)(1) of the Securities Exchange Act of 1934, as amended (the “Act”), this Amended Statement is jointly filed by OGK-3 and INTER RAO UES.  The Statement on Schedule 13D of the Reporting Persons, as amended by this Amended Statement, is referred to herein as the “Statement.”

The ownership percentages contained in this Statement and in the cover pages hereto are based upon information contained in the Issuer’s most recently available filings with the U.S. Securities and Exchange Commission that, as of May 9, 2012, 37,855,742 shares of Common Stock were outstanding.

Item 2.  Identity and Background

Item 2 of the Statement is hereby amended and supplemented as follows:

OGK-3 is an open joint stock company organized under the laws of the Russian Federation.  INTER RAO UES directly owns 38.93% of OGK-3 and indirectly (through JSC “INTER RAO Capital”) owns 33.65% of OGK-3, for an aggregate ownership interest of 72.58%.

In accordance with the provisions of General Instruction C to Schedule 13D, information concerning the executive officers, directors and each person controlling the Reporting Persons, as applicable (collectively, the “Listed Persons”), required by Item 2 of Schedule 13D is provided on Exhibit A hereto and is incorporated by reference herein.

During the past five years, neither of the Reporting Persons nor, to the best of their knowledge, any of the Listed Persons have been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors). During the past five years, neither of the Reporting Persons nor, to the best of their knowledge, any of the Listed Persons were a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

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Item 4.    Purpose of the Transaction

Item 4 of the Statement is hereby amended and supplemented as follows:

On June 8, 2012, the board of directors of OGK-3 approved the sale of all of the Common Stock owned by OGK-3 to JSC “INTER RAO Capital” (“INTER RAO Capital”), a closed joint stock company organized under the laws of the Russian Federation and a wholly-owned subsidiary of INTER RAO UES.  It is the intention of the board of directors of OGK-3 that following the sale of the Common Stock to INTER RAO Capital, OGK-3 will no longer own any shares of Common Stock.  As of the date hereof, no share purchase agreement or other definitive documentation with respect to the sale of the Common Stock has been executed by OGK-3 and INTER RAO Capital and the terms of such sale have not been finalized.  Accordingly, as of the date hereof, OGK-3 continues to own the Common Stock as set forth in this Statement, and as of the date hereof, INTER RAO Capital does not have Section 13(d) beneficial ownership over any of the Common Stock.  INTER RAO UES and OGK-3 have notified the Issuer of this contemplated transaction.  As the contemplated transfer is an intercompany transaction for INTER RAO UES as the parent of both INTER RAO Capital and OGK-3, it is not contemplated that the transaction will have any material effect on the Issuer.

In 2011, OGK-3 entered into a management agreement with Limited Liability Company INTER RAO - Electrical Generation Management, a wholly-owned subsidiary of INTER RAO UES, whereby OGK-3 has agreed to transfer certain management rights and responsibilities to Limited Liability Company INTER RAO - Electrical Generation Management.

The Reporting Persons will review their investment in the Issuer from time to time and may determine (subject to the terms of the Standstill and Support Agreement dated as of May 6, 2011, the Shareholder Rights Agreement dated as of June 23, 2009, as amended, and applicable law) to take any of the actions required to be described in Item 4 of Schedule 13D.  However, except as set forth in this Statement, the Reporting Persons do not have any present plans or proposals that relate to or would result in the occurrence of any of the events specified in clauses (a) through (j) of the instructions to Item 4 of Schedule 13D.

Item 5.    Interest in Securities of the Issuer

The information included in Item 4 of this Statement is hereby incorporated by reference into this Item 5, and Item 5 of the Statement is hereby amended and restated as follows.

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Item 6.            Contracts, Arrangements, Understandings or Relationships with Respect to Securities of the Issuer

Items 2 through 5 are incorporated by reference into this Item 6, and Item 6 is hereby amended and supplemented as follows.

As previously disclosed by the Issuer, pursuant to the Standstill and Support Agreement dated as of May 6, 2011 among the Issuer and the Reporting Persons, two individuals affiliated with INTER RAO UES, Evgeny Rasskazov and Evgeny Miroshnichenko, have been appointed to the board of directors of the Issuer.

Except as described in this Statement, neither the Reporting Persons nor, to the knowledge of the Reporting Persons, any of the Listed Persons has any contract, arrangement, understanding, or relationship (legal or otherwise) with any person with respect to any securities of the Issuer, including but not limited to transfer or voting of such securities, finder’s fees, joint ventures, loan or option arrangements, puts or calls, guarantees of profits, division of profits or loss, or the giving or withholding of proxies.

Item 7.            Materials to be Filed as Exhibits

The following documents are filed as exhibits to this Statement.

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SIGNATURE

After reasonable inquiry and to the best of our knowledge and belief, the undersigned certify that the information set forth in this Statement is true, complete and correct.

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EXHIBIT A

OFFICERS AND DIRECTORS OF OGK-3

Board of Directors

OFFICERS AND DIRECTORS OF INTER RAO UES

Management Board

Board of Directors

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EXHIBIT B

AGREEMENT RELATING TO JOINT FILING OF SCHEDULE 13D/A

In accordance with Rule 13d-1(k)(1)(iii) under the Securities Exchange Act of 1934, as amended, the persons named below agree to the joint filing on behalf of each of them of an Amendment No. 5 to the Statement on Schedule 13D originally filed on March 27, 2009 with respect to the securities of Plug Power Inc.  This Agreement Relating to Joint Filing of Schedule 13D/A shall be filed as an Exhibit to such Statement.