Edgar Filing: NRG ENERGY, INC.

424B3

Filed Pursuant to Rule 424(b)(3)

Registration No. 333-123677

Prospectus Supplement No. 4 dated March 21, 2006

(To Prospectus dated June 2, 2005)

NRG Energy, Inc.

420,000 Shares of 4% Convertible Perpetual Preferred Stock

10,500,000 Shares of Common Stock issuable upon conversion of the Preferred Stock

This Prospectus Supplement supplements the prospectus dated June 2, 2005 (the “Prospectus”) of NRG Energy, Inc., relating to the sale by certain of our stockholders (including their pledgees, donees, assignees, transferees, successors and others who later hold any of the selling stockholders’ interests) of up to 420,000 shares of preferred stock, or 10,500,000 shares of our common stock issuable upon conversion of the preferred stock. You should read this Prospectus Supplement in conjunction with the Prospectus, and this Prospectus Supplement is qualified by reference to the Prospectus, except to the extent that the information in this Prospectus Supplement supersedes the information contained in the Prospectus.

Investing in our preferred stock or common stock involves risks that are described in the “Risk Factors” section beginning on page 6 of the Prospectus.

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

The date of this Prospectus Supplement is March 21, 2006

The table of selling stockholders contained in the Prospectus is hereby superseded by the following table.


				Securities Offered by the
	Ownership Before Offering			Prospectus (1)				Ownership After Offering (2)
Name	Preferred		Common (3)	Preferred		Commons (3)		Preferred		Common		% of Common (4)
1976 Distribution Trust FBO A.R. Lauder/Zinterhofer		6	150		6		150		0		0	*
2000 Revocable Trust FBO A.R. Lauder/Zinterhofer		5	125		5		125		0		0	*
Advent Claymore Enhance Growth & Income Fund		2,435	60,875		2,435		60,875		0		0	*
Advent Convertible Master (Cayman), L.P.		6,723	168,075		6,723		168,075		0		0	*
Alcon Laboratories		641	16,025		641		16,025		0		0	*
AM International EMAC 63 Ltd.		790	19,750		790		19,750		0		0	*
AM Master Fund I, LP		6,916	172,900		6,916		172,900		0		0	*
Anthony Munk		607	15,175		607		15,175		0		0	*
Arlington County Employees Retirement Systems		1,032	25,800		1,032		25,800		0		0	*
Asante Health Systems		205	5,125		205		5,125		0		0	*
BBT Fund, L.P.		8,850	221,250		8,850		221,250		0		0	*
Boston Income Portfolio c/o Eaton Vance Management High Yield Group		1,255	31,375		1,255		31,375		0		0	*
Citigroup Global Markets, Inc.(5)		5,000	125,000		5,000		125,000		0		0	*
City of New York Fire Dept Pension Fund High Yield(9)		125	3,125		125		3,125		0		0	*
City of New York Police Pension Fund High Yield		275	6,875		275		6,875		0		0	*
City of New York Teachers Retirement System High Yield(6)		375	9,375		375		9,375		0		0	*
City University of New York		215	5,375		215		5,375		0		0	*
CNHCA Master Account, LP		5,500	137,500		5,500		137,500		0		0	*
Coastal Convertibles Ltd.		1,500	37,500		1,500		37,500		0		0	*
Concentrated Alpha Partners LP		6,750	168,750		6,750		168,750		0		0	*
DBAG London		11,000	275,000		11,000		275,000		0		0	*
Delaware Dividend Income Fund		1,500	37,500		1,500		37,500		0		0	*
Delaware Public Employees Retirement Systems		1,857	46,425		1,857		46,425		0		0	*
Deutsche Bank Securities Inc.		1,500	37,500		1,500		37,500		0		0	*


				Securities Offered by the
	Ownership Before Offering			Prospectus (1)				Ownership After Offering (2)
Name	Preferred		Common (3)	Preferred		Commons (3)		Preferred		Common		% of Common (4)
Diversified High Yield Bond Fund c/o Eaton Vance Management High Yield Group		245	6,125		245		6,125		0		0		*
Drawbridge Convertible I Ltd.		489	12,225		489		12,225		0		0		*
Drawbridge Convertible II Ltd.		156	3,900		156		3,900		0		0		*
Drawbridge Global Macro Masterfund Ltd.		3,310	82,750		3,310		82,750		0		0		*
ELCA Unscreened — High Yield(6)		275	6,875		275		6,875		0		0		*
FIST Convertible Secs FD		10,000	250,000		10,000		250,000		0		0		*
Fidelity Financial Trust: Fidelity Strategic Dividend & Income Fund(7)(8)		4,900	101,635		3,900		97,500		0		0		*
Fore Convertible Master Fund, Ltd.		25,220	630,500		25,220		630,500		0		0		*
Fore Erisa Fund, Ltd.		2,790	69,750		2,790		69,750		0		0		*
Frontpoint Convertible Arbitrage Fund LP		5,000	125,000		5,000		125,000		0		0		*
GLG Market Neutral Fund		22,000	550,000		22,000		550,000		0		0		*
Grace Convertible Arbitrage Fund, Ltd.		7,000	175,000		7,000		175,000		0		0		*
Grady Hospital		201	5,025		201		5,025		0		0		*
Guggenheim Portfolio Company VIII (Cayman) Ltd.		2,511	62,775		2,511		62,775		0		0		*
Guggenheim Portfolio Company XXXI, LLC		5,000	125,000		5,000		125,000		0		0		*
Hallmark Master Trust High Yield Fund c/o Eaton Vance Management High Yield Group		70	1,750		70		1,750		0		0		*
HFR CA Opportunity Mgt. Trst.		340	8,500		340		8,500		0		0		*
HFR CA Select Fund		750	18,750		750		18,750		0		0		*
HFR RVA Combined Master Trust		2,000	50,000		2,000		50,000		0		0		*
High Income Portfolio c/o Eaton Vance Management High Yield Group		865	21,625		865		21,625		0		0		*
IAM National Pension Fund(6)		175	4,375		175		4,375		0		0		*
Independence Blue Cross		623	15,575		623		15,575		0		0		*
Industriens Pensionsforsikring(6)		175	4,375		175		4,375		0		0		*


				Securities Offered by the
	Ownership Before Offering			Prospectus (1)				Ownership After Offering (2)
Name	Preferred		Common (3)	Preferred		Commons (3)		Preferred		Common		% of Common (4)
ING Convertible Fund		1,920	48,000		1,920		48,000		0		0	*
ING CP Convertible Portfolio		80	2,000		80		2000		0		0	*
ING MFS Utilities Portfolio		40	79,520		40		1,000		0		78,520	*
ING T. RowePrice Capital Appreciation Portfolio(6)		12,000	300,000		12,000		300,000		0		0	*
Institutional Benchmarks Master Fund, Ltd.		1,500	37,500		1,500		37,500		0		0	*
Intl Union of Operating Engineers (ENG) c/o Eaton Vance Management High Yield Group		15	375		15		375		0		0	*
JHVST MidCap Value B		200	52,200		200		5,000		0		47,200	*
JMG Capital Partners, Inc		34,500	862,500		34,500		862,500		0		0	*
JMG Triton Offshore Ltd.		2,850	71,250		2,850		71,250		0		0	*
John Hancock Funds II — Spectrum Income Fund(6)		100	2,500		100		2,500		0		0	*
John Hancock Trust — Spectrum Income Trust(6)		100	2,500		100		2,500		0		0	*
John Hancock Trust Utilities Trust		100	133,640		100		2,500		0		131,140	*
John Hancock Variable Series Trust I — Mid Cap Value(6)		200	31,800		200		5,000		0		26,800	*
JP Morgan Securities, Inc.		2,500	62,500		2,500		62,500		0		0	*
Kamunting Street Master Fund, Ltd.		22,500	562,500		22,500		562,500		0		0	*
KBC Financial Products USA, Inc.		8,955	223,875		8,955		223,875		0		0	*
KDC Convertible Arbitrage Fund LP		3,000	75,000		3,000		75,000		0		0	*
Laborers District Council & Contractors Pension FD of Ohio(6)		200	19,400		200		5,000		0		14,400	*
LIJ Invest — Global High Yield		275	6,875		275		6,875		0		0	*
Lyxor		465	11,625		465		11,625		0		0	*
Lyxor/AM Investment Fund Ltd.		988	24,700		988		24,700		0		0	*
Lyxor/Silverado Fund LTD		1,550	38,750		1,550		38,750		0		0	*
Man Mac I, Ltd.		9,390	234,750		9,390		234,750		0		0	*
McMahan Securities Co. LP		45	1,125		45		1,125		0		0	*


				Securities Offered by the
	Ownership Before Offering			Prospectus (1)				Ownership After Offering (2)
Name	Preferred		Common (3)	Preferred		Commons (3)		Preferred		Common		% of Common (4)
MFS Utilities Fund, a Series of MFS Series Trust VI		1,355	1,614,875		1,355		33,875		0		1,581,000		1.15%
MFS Variable Insurance Trust -
MFS Utilities Series		820	874,400		820		20,500		0		853,900		*
MFS/Sun Life Series Trust:
Utilities Series		324	363,800		324		8,100		0		355,700		*
MSS Convertible Arbitrage 1		20	500		20		500		0		0		*
National Bank of Canada		1,186	29,650		1,186		29,650		0		0		*
New Orleans Firefighters Pension/Relief Fund		126	3,150		126		3,150		0		0		*
New York City Employees Retirement Systems Enhanced Fund(6)		475	11,875		475		11,875		0		0		*
Newport Alternative Income Fund		2,972	74,300		2,972		74,300		0		0		*
NMS Services (Cayman) Inc.		1,011	25,275		1,011		25,275		0		0		*
Northern Income Equity Fund		2,460	61,500		2,460		61,500		0		0		*
Occidental Petroleum Corporation		114	2,850		114		2,850		0		0		*
Pebble Limited Partnership		2,083	52,075		2,083		52,075		0		0		*
Penn Series Flexibly Managed Fund		5,600	140,000		5,600		140,000		0		0		*
Penn Series High Yield Bond Fund		200	5,000		200		5,000		0		0		*
PensionsInvest — Global High Yield(6)		250	6,250		250		6,250		0		0		*
PFA Invest — Global High Yield(6)		450	11,250		450		11,250		0		0		*
PIMCO Convertible Fund		500	12,500		500		12,500		0		0		*
Policeman and Fireman Retirement System of the City of Detroit		500	12,500		500		12,500		0		0		*
Pro-Mutual		1,357	33,925		1,357		33,925		0		0		*
RWDSU Local 338 High Yield Fund c/o Eaton Vance Management High Yield Fund		20	500		20		500		0		0		*
S.A.C. Arbitrage Fund, LLC		8,000	200,000		8,000		200,000		0		0		*
Sage Capital Management LLC		3,000	75,000		3,000		75,000		0		0		*
Salomon Brothers Asset Management, Inc.(9)		6,600	165,000		6,600		165,000		0		0		*
SEPTA High Yield Fund c/o Eaton Vance Management High Yield Group		20	500		20		500		0		0		*


				Securities Offered by the
	Ownership Before Offering			Prospectus (1)				Ownership After Offering (2)
Name	Preferred		Common (3)	Preferred		Commons (3)		Preferred		Common		% of Common (4)
Severn River Master Fund c/o Morgan Stanley		1,000	25,000		1,000		25,000		0		0		*
Silver Point Capital Fund LP		1,365	1,042,333		1,365		34,125		0		1,008,208		*
Silver Point Capital Offhsore Fund, Ltd.		2,135	1,654,740		2,135		53,375		0		1,601,365		1.17%
Silverado Arbitrage Trading, Ltd.		500	22,500		500		12,500		0		10,000		*
SOCS Ltd.		10,000	260,000		8,000		250,000		2,000		10,000		*
Sphinx Fund		140	3,500		140		3,500		0		0		*
SRI Fund, L.P.		1,500	37,500		1,500		37,500		0		0		*
Stanfield Offshore Leveraged Assets, Ltd.		10,500	693,213		10,500		262,500		0		430,713		*
T. RowePrice Capital Appreciation Fund(6)		33,600	840,000		33,600		840,000		0		0		*
T. RowePrice High Yield Fund(6)		4,350	108,750		4,350		108,750		0		0		*
T. RowePrice Mid-Cap Value Fund(6)		12,000	1,132,500		12,000		300,000		0		832,500		*
The New America High Income Fund		375	9,375		375		9,375		0		0		*
TQA Master Fund, LTD.		870	21,750		870		21,750		0		0		*
TQA Masters Plus Fund, LTD.		1,510	37,750		1,510		37,750		0		0		*
TRP Institutional High Yield Fund		375	9,375		375		9,375		0		0		*
TRP Invest — Global High Yield(6)		1,200	51,250		350		30,000		850		21,250		*
TRP SICAV Global High Yield Bond Fund		1,125	28,125		1,125		28,125		0		0		*
Trustmark Insurance		393	9,825		393		9,825		0		0		*
UBS AG London F/B/O HFS		5,000	125,000		5,000		125,000		0		0		*
UBS AG London FBO PFEL		18,500	462,500		18,500		462,500		0		0		*
UBS AG london FBO WCBP		20,000	500,000		20,000		500,000		0		0		*
UBS O’Connor LLC F/B/O O’Connor Global Convertiable Arbitrage Master Ltd.		5,000	125,000		5,000		125,000		0		0		*
Volkswagen High Yield Bond Fund c/o Eaton Vance Management High Yield Group		10	250		10		250		0		0		*
Whitebox Convertible Arbitrage Partners LP		26,000	650,000		26,000		650,000		0		0		*
Whitebox Diversified Convertible Arbitrage Partners LP		5,000	125,000		5,000		125,000		0		0		*


				Securities Offered by the
	Ownership Before Offering			Prospectus (1)				Ownership After Offering (2)
Name	Preferred		Common (3)	Preferred		Commons (3)		Preferred		Common		% of Common (4)
Xavex – Convertible Arbitrage 7 Fund		150	3,750		150		3,750		0		0		*
Zazove Convertible Arbitrage Fund, LP		4,000	100,000		4,000		100,000		0		0		*
Zazove Hedged Convertible Fund, LP		2,000	50,000		2,000		50,000		0		0		*
Zurich Institutional Benchmarks Master Fund LTD c/o TQA Investors, LLC		180	4,500		180		4,500		0		0		*
Zurich Institutional Benchmarks Master Fund Ltd. c/o Forest Investment LLC		2,061	51,525		2,061		51,525		0		0		*


*	Less than 1%.


(1)	Amounts indicated may be in excess of the total amount registered due to sales or transfers exempt from the registration requirements of the Securities Act of 1933, as amended, since the date upon which the selling stockholders provided to us the information regarding their preferred stock.

(2)	The information regarding the beneficial ownership after resale of shares is based on the assumption that each selling stockholder will sell all of the shares of preferred stock and common stock owned by the selling stockholder and covered by the Prospectus.

(3)	Unless otherwise indicated, includes all shares of common stock issuable upon conversion of the preferred stock and assumes a conversion price of $40.00 per share, which is equal to an approximate conversion rate of 25 shares per share of preferred stock. However, this conversion price will be subject to adjustment as described under “Description of the Preferred Stock — Conversion Rights” in the Prospectus. As a result, the number of shares of common stock beneficially owned prior to this offering and the number of shares of common stock offered hereby may increase or decrease in the future.

(4)	Based on 136,975,275 shares of common stock outstanding as of March 13, 2006.

(5)	Citigroup Global Markets Inc. was a co-placement agent on the issuance of the preferred stock.

(6)	T. Rowe Price Associates, Inc. serves as investment adviser with power to direct investments and/or sole power to vote the shares owned by certain funds and accounts subject this footnote, as well as shares owned by certain other individual and institutional investors. For purposes of reporting requirements of the Securities and Exchange Act of 1934, T. Rowe Price Associates, Inc. may be deemed to be the beneficial owner of all of the shares listed above that are subject to this footnote; however, T. Rowe Price Associates, Inc. expressly disclaims that it is in fact the beneficial owner of such securities. T. Rowe Price Associates, Inc. is the wholly owned subsidiary of T. Rowe Price Group, Inc., which is a publicly traded financial services holding company.

(7)	The entity is a registered investment fund advised by Fidelity Management & Research Company (“FMR Co.”), a registered investment adviser under the Investment Advisers Act of 1940, as amended. FMR Co., 82 Devonshire Street, Boston, Massachusetts 02190, a wholly-owned subsidiary of FMR Corp. and an investment adviser registered under Section 203 of the Investment Advisers Act of 1940, is the beneficial owner of 2,402,699 shares of our outstanding common stock as a result of acting as investment adviser to various investment companies registered under Section 8 of the Investment Company Act of 1940.

(8)	Based on information provided by the selling stockholder and, in addition to the preferred stock and common stock covered by this prospectus, includes beneficial ownership of our 5.75% Mandatory Convertible Preferred Stock, as well as the common stock to be issued upon conversion of such preferred stock.

(9)	Salomon Brothers Asset Management, Inc. acts as discretionary investment advisor with respect to certain accounts that hold the preferred stock. Accordingly, Salomon Brothers Asset Management, Inc. may be deemed to be the beneficial owner of such preferred stock. Salomon Brothers Asset Management, Inc. is the beneficial owner and, therefore, the Selling Stockholder of the following accounts: General Motors Investment Corp. (5,000 shares), General Motors Broad Mandate (600 shares) and Smith Barney Convertible Fund (1,000 shares).