SEC FORM 3

SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person^*

MARXE AUSTIN W & GREENHOUSE DAVID M

(Last)

(First)

(Middle)

C/O SPECIAL SITUATIONS FUNDS

527 MADISON AVENUE, SUITE 2600

(Street)

NEW YORK

10022

(City)

(State)

(Zip)

2. Date of Event Requiring Statement (Month/Day/Year)
03/23/2012

3. Issuer Name and Ticker or Trading Symbol
PLUG POWER INC [ PLUG ]

4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

Director	X	10% Owner
Officer (give title below)		Other (specify below)

5. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Stock	8,511,620⁽¹⁾	I⁽¹⁾	By Limited Partnership⁽¹⁾

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
1. Title of Derivative Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
Warrant	05/25/2011	05/31/2016	Common Stock	2,801,762⁽²⁾⁽³⁾	$2.27	I⁽²⁾⁽³⁾	By Limited Partnerships⁽²⁾⁽³⁾

Explanation of Responses:

1. This is a joint filing by Austin W. Marxe (Marxe) and David M. Greenhouse (Greenhouse). They share voting and investment control over all securities owned by Special Situations Fund III QP, L.P. (SSFQP), Special Situations Cayman Fund, L.P. (Cayman), Special Situations Private Equity Fund, L.P. (PE), Special Situations Technology Fund, L.P. (Tech) and Special Situations Technology Fund II, L.P. (Tech2). 3,158,900 shares of Common Stock are held by SSFQP, 950,000 shares of Common Stock are held by Cayman, 581,385 shares of Common Stock are held by PE, 530,942 shares of Common Stock are held by Tech and 3,290,393 shares of Common Stock are held by Tech2. The interest of Marxe and Greenhouse in the shares of Common Stock owned by SSFQP, Cayman, PE, Tech and Tech2 is limited to the extent of his pecuniary interest.

2. This is a joint filing by Austin W. Marxe (Marxe) and David M. Greenhouse (Greenhouse). They share voting and investment control over all securities owned by, Special Situations Private Equity Fund, LP (PE), Special Situations Technology Fund, L.P. (Tech) and Special Situations Technology Fund II, L.P. (Tech2). 419,145 Warrants are owned by PE, 231,239 Warrants are owned by Tech and 1,469,616 Warrants are owned by Tech2. The interest of Marxe and Greenhouse in the shares of Warrants owned by PE, Tech and Tech2 are limited to the extent of his pecuniary interest.

3. The warrant may be exercised to the extent that the total number of shares of Common Stock then beneficially owned does not exceed 4.99% of the outstanding shares. The Holder may request an increase up to 9.99% of the outstanding shares, effective on the 61st day after notice is given to the Company.

	Austin W. Marxe	04/02/2012
	David M. Greenhouse	04/02/2012
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 5 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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