Ownership Submission
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, 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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(Print or Type Responses)
1. Name and Address of Reporting Person *
  KKR Millennium GP Energy LLC
2. Date of Event Requiring Statement (Month/Day/Year)
08/09/2006
3. Issuer Name and Ticker or Trading Symbol
NRG ENERGY, INC. [NRG]
(Last)
(First)
(Middle)
C/O KOHLBERG KRAVIS ROBERTS & CO. L.P., 9 WEST 57TH STREET
4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) __X__ Other (specify below)
See Remarks
5. If Amendment, Date Original Filed(Month/Day/Year)
(Street)

NEW YORK, NY 10019
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 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, par value $0.01 per share 8,199,882
I
See footnotes (1) (2) (3) (4)
Common stock, par value $0.01 per share 431,572
I
See footnotes (1) (2) (3) (4)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. SEC 1473 (7-02)
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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 of Derivative Security: Direct (D) or Indirect (I)
(Instr. 5)
6. Nature of Indirect Beneficial Ownership
(Instr. 5)
Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
KKR Millennium GP Energy LLC
C/O KOHLBERG KRAVIS ROBERTS & CO. L.P.
9 WEST 57TH STREET
NEW YORK, NY 10019
    X   See Remarks
KKR Millennium Fund Energy LP
C/O KOHLBERG KRAVIS ROBERTS & CO. L.P.
9 WEST 57TH STREET
NEW YORK, NY 10019
    X   See Remarks
KKR Partners III, L.P.
C/O KOHLBERG KRAVIS ROBERTS & CO. L.P.
9 WEST 57TH STREET
NEW YORK, NY 10019
    X   See Remarks
KKR Associates Millennium Energy L.P.
C/O KOHLBERG KRAVIS ROBERTS & CO. L.P.
9 WEST 57TH STREET
NEW YORK, NY 10019
    X   See Remarks
KRAVIS HENRY R
C/O KOHLBERG KRAVIS ROBERTS & CO. L.P.
9 WEST 57TH STREET
NEW YORK, NY 10019
    X   See Remarks
ROBERTS GEORGE R
C/O KOHLBERG KRAVIS ROBERTS & CO. L.P.
9 WEST 57TH STREET
NEW YORK, NY 10019
    X   See Remarks
FISHER TODD A
C/O KOHLBERG KRAVIS ROBERTS & CO. L.P.
9 WEST 57TH STREET
NEW YORK, NY 10019
    X   See Remarks
Garaialde Jacques
C/O KOHLBERG KRAVIS ROBERTS & CO. L.P.
9 WEST 57TH STREET
NEW YORK, NY 10019
    X   See Remarks
GOLKIN PERRY
C/O KOHLBERG KRAVIS ROBERTS & CO. L.P.
9 WEST 57TH STREET
NEW YORK, NY 10019
    X   See Remarks
GREENE JAMES H JR
C/O KOHLBERG KRAVIS ROBERTS & CO. L.P.
9 WEST 57TH STREET
NEW YORK, NY 10019
    X   See Remarks

Signatures

/s/ William J. Janetschek, by power of attorney for all Reporting Persons 08/11/2006
**Signature of Reporting Person Date

Explanation of Responses:

* 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).
(1) KKR Millennium Fund (Energy) L.P. ("Millennium Energy") and KKR Partners III, L.P. (Series I) ("KKR Partners", and together with Millennium Energy, the "KKR Funds") hold 8,199,882 and 431,572 shares, respectively, of common stock of NRG Energy, Inc. (the "Common Stock") reported on this Form 3. As general partner of Millennium Energy, KKR Associates Millennium (Energy) L.P. ("KKR Associates") may be deemed to be the beneficial owner of the Common Stock held by Millennium Energy. As the general partner of KKR Associates, KKR Millennium GP (Energy) LLC ("KKR GP LLC") also may be deemed to be the beneficial owner of the Common Stock held by Millennium Energy. As general partner of KKR Partners, KKR GP LLC may be deemed to be the beneficial owner of the Common Stock held by KKR Partners.
(2) Henry R. Kravis, George R. Roberts, Todd A. Fisher, Jacques Garaialde, Perry Golkin, James H. Greene, Jr., Johannes P. Huth, Marc S. Lipschultz, Michael W. Michelson, Alexander Navab and Paul E. Raether are the members of KKR GP LLC (the "Members"), and as such may be deemed to share beneficial ownership of any Common Stock that KKR GP LLC may be deemed to beneficially own. Each Reporting Person disclaims beneficial ownership of the Common Stock, except to the extent of its or his pecuniary interest therein.
(3) The filing of this statement shall not be deemed an admission that, for purposes of Section 16 of the Securities Exchange Act of 1934 or otherwise, any Reporting Person is the beneficial owner of any Common Stock covered by this statement.
(4) Due to limitations on Form 3, certain persons described as beneficial owners or deemed beneficial owners of the securities reported on this Form 3 are filing as reporting persons on a separate Form 3.
 
Remarks:
As described in Amendment No. 1 to Schedule 13D filed on August 11, 2006 with respect to the Common Stock by the KKR Funds, KKR Associates, KKR GP LLC and the other filers listed on the signature pages thereto (the "Other 13D Filers"), the KKR Funds and certain Other 13D Filers may be deemed to be a "group" under Section 13(d) of the Securities Exchange Act and each of the KKR Funds, KKR Associates and KKR GP LLC may be deemed to have beneficial ownership of 10% or more of the Common Stock.  Each Member may therefore be deemed to share beneficial ownership of 10% or more of the Common Stock.  Each Reporting Person expressly disclaims membership in any such group under Section 13(d) of the Securities Exchange Act or for any other purpose.        Exhibit 24 -  Powers of Attorney Exhibit 99 - Joint Filer Information

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