Sec Form 4 Filing - BLACKSTONE MANAGEMENT ASSOCIATES IV LLC @ NRG ENERGY, INC. - 2006-08-15

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person BLACKSTONE MANAGEMENT ASSOCIATES IV LLC 2. Issuer Name and Ticker or Trading Symbol NRG ENERGY, INC. [ NRG] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) X __ Other (specify below) See Remarks (Last) (First) (Middle) C/O THE BLACKSTONE GROUP, 345 PARK AVENUE 3. Date of Earliest Transaction (MM/DD/YY) 08/15/2006 (Street) NEW YORK, NY10154 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock, par value $0.01 per share 08/15/2006 S 3,309,582 D $ 48.41 ( 1 ) 3,309,583 I See footnotes ( 1 ) ( 2 ) ( 3 ) ( 4 ) Common Stock, par value $0.01 per share 08/15/2006 S 629,828 D $ 48.41 ( 1 ) 629,827 I See footnotes ( 1 ) ( 2 ) ( 3 ) ( 4 ) Common Stock, par value $0.01 per share 08/15/2006 S 57,685 D $ 48.41 ( 1 ) 57,685 I See footnotes ( 1 ) ( 2 ) ( 3 ) ( 4 ) Common Stock, par value $0.01 per share 08/15/2006 S 208,160 D $ 48.41 ( 1 ) 208,160 I See footnotes ( 1 ) ( 2 ) ( 3 ) ( 4 ) Common Stock, par value $0.01 per share 08/15/2006 S 7,625 D $ 48.41 ( 1 ) 7,626 I See footnotes ( 1 ) ( 2 ) ( 3 ) ( 4 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other BLACKSTONE MANAGEMENT ASSOCIATES IV LLC C/O THE BLACKSTONE GROUP 345 PARK AVENUE NEW YORK, NY10154 X See Remarks Blackstone TG Capital Partners IV L.P. C/O THE BLACKSTONE GROUP 345 PARK AVENUE NEW YORK, NY10154 X See Remarks Blackstone TG Capital Partners IV-B L.P. C/O THE BLACKSTONE GROUP 345 PARK AVENUE NEW YORK, NY10154 X See Remarks BLACKSTONE CAPITAL PARTNERS IV-A LP C/O THE BLACKSTONE GROUP 345 PARK AVENUE NEW YORK, NY10154 X See Remarks BLACKSTONE FAMILY INVESTMENT PARTNERSHIP IV-A LP C/O THE BLACKSTONE GROUP 345 PARK AVENUE NEW YORK, NY10154 X See Remarks Blackstone Participation Partnership IV L.P. C/O THE BLACKSTONE GROUP 345 PARK AVENUE NEW YORK, NY10154 X See Remarks PETERSON PETER G C/O THE BLACKSTONE GROUP 345 PARK AVENUE NEW YORK, NY10154 X See Remarks SCHWARZMAN STEPHEN A C/O THE BLACKSTONE GROUP 345 PARK AVENUE NEW YORK, NY10154 X See Remarks Signatures /s/ David Foley (on behalf of Blackstone Management Associates IV L.L.C.) 08/16/2006 Signature of Reporting Person Date

Explanation of Responses:

( 1 )On August 15, 2006, Blackstone TG Capital Partners IV L.P. ("BCP IV"), Blackstone TG Capital Partners IV-B L.P. ("BCP IV-B"), Blackstone Capital Partners IV-A L.P. ("BCP IV-A"), Blackstone Family Investment Partnership IV-A L.P. ("BFIP") and Blackstone Participation Partnership IV L.P. ("BPP", and together with BCP IV, BCP IV-B, BCP IV-A and BFIP, the "Blackstone Funds") sold respectively 3,309,582, 629,828, 57,685, 208,160 and 7,625 shares (4,212,880 shares in total) of NRG Energy, Inc.'s common stock (the "Common Stock"), to Morgan Stanley & Co. Incorporated at a price of $48.41 per share (the "Resale"). Following completion of the Resale, BCP IV, BCP IV-B, BCP IV-A, BFIP and BPP directly own respectively 3,309,583, 629,827, 57,685, 208,160 and 7,626 shares of Common Stock reported as beneficially owned in the above table. ( 2 )Blackstone Management Associates IV L.L.C. ("BMA") is the sole general partner of each of the Blackstone Funds and, as such, may be deemed to share beneficial ownership of the shares of Common Stock held by the Blackstone Funds. Messrs. Peter G. Peterson and Stephen A. Schwarzman are the founding members of BMA and, as such, may be deemed to share beneficial ownership of the shares of Common Stock held by the Blackstone Funds. ( 3 )Information with respect to each of the Reporting Persons is given solely by such Reporting Persons, and no Reporting Person has responsibility for the accuracy or completeness of information supplied by another Reporting Person. ( 4 )Pursuant to Rule 16a-1(a)(4) of the Securities Exchange Act of 1934, as amended, each of the Reporting Persons, other than the Blackstone Funds, herein states that this filing shall not be deemed an admission that he or it is the beneficial owner of any of the shares of Common Stock covered by this Statement. Each of BMA, Messrs. Peter G. Peterson and Stephen A. Schwarzman disclaims beneficial ownership of the Common Stock, except to the extent of its or his pecuniary interest in such shares of Common Stock.

Remarks: As described in Amendment No. 1 to Schedule 13D ("Amendment No. 1") filed on August 11, 2006 with respect to the Common Stock by the Reporting Persons and the other filers listed on the signature pages thereto, as of the date of Amendment No. 1, the Blackstone Funds and certain other Funds (as defined in Amendment No. 1) may have been deemed to be a "group" under Section 13(d) of the Securities Exchange Act and accordingly each Reporting Person may have been deemed to have beneficial ownership of 10% or more of the Common Stock. Following the completion of the Resale, the Reporting Persons are not presently acting in a manner that could deem them to be a "group" with the other Funds within the meaning of Section 13(d) of the Securities Exchange Act with respect to the Common Stock. Each Reporting Person expressly disclaims membership in any such group for the purposes of Section 13(d) of the Securities Exchange Act or for any other purpose. Please see attached Joint Filer Information for signatures of other Reporting Persons.

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* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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