Filed by Exelon Corporation

(Commission File No. 1-16169)

Pursuant to Rule 425 under the Securities

Act of 1933

Subject Company:

NRG Energy, Inc.

(Commission File No. 1-15891)

Safe Harbor Statement

This filing does not constitute an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval. This filing relates to a transaction with NRG proposed by Exelon, which may become the subject of a registration statement filed with the Securities and Exchange Commission (the “SEC”). This material is not a substitute for the prospectus/proxy statement Exelon Corporation intends to file with the SEC regarding the proposed transaction or for any other document which Exelon may file with the SEC and send to Exelon or NRG stockholders in connection with the proposed transaction. INVESTORS AND SECURITY HOLDERS OF EXELON AND NRG ARE URGED TO READ ANY SUCH DOCUMENTS FILED WITH THE SEC CAREFULLY IN THEIR ENTIRETY WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION.

Investors and security holders will be able to obtain free copies of any documents filed with the SEC by Exelon through the web site maintained by the SEC at www.sec.gov. Free copies of any such documents can also be obtained by directing a request to the Exelon Investor Relations Department, Exelon Corporation, 10 South Dearborn, Chicago, Illinois 60603.

Exelon and its directors and executive officers and other persons may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction. Information regarding Exelon’s directors and executive officers is available in its Annual Report on Form 10-K for the year ended December 31, 2007, which was filed with the SEC on February 7, 2008, and its proxy statement for its 2008 Annual Meeting of Shareholders, which was filed with the SEC on March 20, 2008. Other information regarding the participants in a proxy solicitation and a description of their direct and indirect interests, by security holdings or otherwise, will be contained in a proxy statement filed in connection with the proposed transaction.

All information in this filing concerning NRG, including its business, operations, and financial results, was obtained from public sources. While Exelon has no knowledge that any such information is inaccurate or incomplete, Exelon has not had the opportunity to verify any of that information.

This filing includes forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These forward-looking statements include, for example, statements regarding benefits of the proposed merger, integration plans and expected synergies. There are a number of risks and uncertainties that could cause actual results to differ materially from the forward-looking statements made herein. The factors that could cause actual results to differ materially from these forward-looking statements include Exelon’s ability to achieve the synergies contemplated by the proposed transaction, Exelon’s ability to promptly and effectively integrate the businesses of NRG and Exelon, and the timing to consummate the proposed

transaction and obtain required regulatory approvals as well as those discussed in (1) Exelon’s 2007 Annual Report on Form 10-K in (a) ITEM 1A. Risk Factors, (b) ITEM 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations and (c) ITEM 8. Financial Statements and Supplementary Data: Note 19; (2) Exelon’s Third Quarter 2008 Quarterly Report on Form 10-Q in (a) Part II, Other Information, ITEM 1A. Risk Factors and (b) Part I, Financial Information, ITEM 1. Financial Statements: Note 12; and (3) other factors discussed in Exelon’s filings with the SEC. Readers are cautioned not to place undue reliance on these forward-looking statements, which apply only as of the date of this filing. Exelon does not undertake any obligation to publicly release any revision to its forward-looking statements to reflect events or circumstances after the date of this filing.

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On November 10-12, 2008, Exelon will participate in the Edison Electric Institute Financial Conference. The slides included in Exelon’s conference materials that concern the proposed NRG transaction follow.

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Exelon Corporation Christopher Crane President and Chief Operating Officer Edison Electric Institute Financial Conference November 10-12, 2008

2 Forward-Looking Statements This presentation includes forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These forward-looking statements include, for example, statements regarding benefits of the proposed merger, integration plans and expected synergies.  There are a number of risks and uncertainties that could cause actual results to differ materially from the forward- looking statements made herein.   The factors that could cause actual results to differ materially from these forward-looking statements include Exelon’s ability to achieve the synergies contemplated by the proposed transaction, Exelon’s ability to promptly and effectively integrate the businesses of NRG and Exelon, and the timing to consummate the proposed transaction and obtain required regulatory approvals as well as those discussed in (1) Exelon’s 2007 Annual Report on Form 10-K in (a) ITEM 1A. Risk Factors, (b) ITEM 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations and (c) ITEM 8. Financial Statements and Supplementary Data: Note 19; (2) Exelon’s Third Quarter 2008 Quarterly Report on Form 10-Q in (a) Part II, Other Information, ITEM 1A. Risk Factors and (b) Part I, Financial Information, ITEM 1. Financial Statements: Note 12; and (3) other factors discussed in Exelon’s filings with the SEC.  Readers are cautioned not to place undue reliance on these forward-looking statements, which apply only as of the date of this filing.  Exelon does not undertake any obligation to publicly release any revision to its forward-looking statements to reflect events or circumstances after the date of this filing. All information in this presentation concerning NRG, including its business, operations, and financial results, was obtained from public sources.  While Exelon has no knowledge that any such information is inaccurate or incomplete, Exelon has not had the opportunity to verify any of that information.

3 Important Additional Information This communication does not constitute an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval.  This presentation relates to a transaction with NRG proposed by Exelon, which may become the subject of a registration statement filed with the Securities and Exchange Commission (the “SEC”).  This material is not a substitute for the prospectus/proxy statement Exelon intends to file with the SEC regarding the proposed transaction or for any other document which Exelon may file with the SEC and send to Exelon or NRG stockholders in connection with the proposed transaction. INVESTORS AND SECURITY HOLDERS OF EXELON AND NRG ARE URGED TO READ ANY SUCH DOCUMENTS FILED WITH THE SEC CAREFULLY IN THEIR ENTIRETY WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION.  Exelon and its directors and executive officers and other persons may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction.  Information regarding Exelon’s directors and executive officers is available in its Annual Report on Form 10-K for the year ended December 31, 2007, which was filed with the SEC on February 7, 2008, and its proxy statement for its 2008 Annual Meeting of Shareholders, which was filed with the SEC on March 20, 2008.  Other information regarding the participants in a proxy solicitation and a description of their direct and indirect interests, by security holdings or otherwise, will be contained in a proxy statement filed in connection with the proposed transaction.

4 Exelon Key Messages • Consistent with Exelon Protect and Grow Strategy • Earnings and cash accretion • Clear value creation • Meets NRG’s “Five Imperatives” Exelon Financial Outlook • 2009 operating guidance of $4.00 - $4.30/share • Managing costs and driving productivity • Significant uplift in 2011 - operating earnings of ~$5.00-$6.00/share (1) (1)  Illustrative.  Provided solely to illustrate possible future outcomes that are based on a number of different assumptions, all of which are subject to uncertainties and should not be relied upon as earnings guidance or a forecast of future results. Compelling Offer for NRG

5 A Compelling Opportunity for Value Creation • Exelon offered to acquire all outstanding common shares of NRG in an all stock transaction – Fixed exchange ratio of 0.485 Exelon share for each NRG common share – Offer represents a 37% premium to October 17th closing price for NRG • Combined Entity Creates Value By: – Providing earnings and cash accretion – Creating an exceptional growth platform – Operating in the most attractive markets – Utilizing a premier balance sheet – Allowing Exelon to unlock NRG’s value – Giving NRG’s shareholders the opportunity to participate in future value – Presenting manageable regulatory hurdles to close

6 Transaction Is Accretive (1) Does not include purchase accounting. One-time cost to achieve of ~$100 million (pre-tax) and transaction and other costs of $654 million excluded. (2) Free cash flow defined as cash flow from operations less capital expenditures. (3) Based solely on I/B/E/S estimates for Exelon and NRG as of 10/31/08.  Not necessarily representative of either company’s internal forecasts.  Provided for illustration only.  Not intended as earnings guidance or as a forecast of expected results. (4)  Assumes refinancing of ~$8 billion of NRG debt at an interest rate of 10%. (5) Pro forma numbers in Exelon’s internal forecasts are somewhat lower and accretion is approximately breakeven in 2011. Operating Earnings per share 1 Free cash flow 2 per share $3.82 $4.29 $4.69 2010E 2011E 2012E $2.83 $2.91 $3.70 2010E 2011E 2012E $3.04 N/A N/A 2010E 2011E 2012E $4.42 $5.86 $6.16 2010E 2011E 2012E $4.03 N/A N/A 2010E 2011E 2012E 32.5% $4.83 $6.01 $6.43 2010E 2011E 2012E 9.4% 2.5% 4.3% Based on analyst consensus estimates for both companies, the deal will be accretive in the first full year following closing Exelon  NRG Pro forma 5 • Synergies • Increased interest expense (4) • Synergies • Increased interest expense (4) 3 3 1 2

7 Combination Creates Substantial Synergies Exelon Operations & Maintenance: $4,289 NRG Maintenance & Other Opex: $950 General & Admin Expenses: $309 Other COGS: $454 Pro Forma Combined Non-fuel Expenses:    $6,002 Estimated Annual Cost Savings: $180 - $300 2 % of Combined Expenses: 3%-5% Costs to Achieve $100 NPV of Synergies: $1,500-$3,000 ($ in Millions) Reflects no revenue or fuel cost synergies. Excludes transaction and other costs of $654 million and excludes increased interest expense related to refinancing of NRG debt. (1) Company 10-K for 2007 and investor presentations. (2) Based on a preliminary analysis of publicly available information.  Subject to due diligence investigation. 1 Transaction creates $1.5 – $3 billion of value through synergies – with opportunity for more 1

Clear Value under Multiple Scenarios Gas price is long-term price in 2008 $/MMBtu; coal price is long-term price in 2008 $/ton for PRB8800 excluding transportation; new build cost is long-term combined cycle cost in PJM in 2008 overnight $/kW; carbon year is year in which national cap and trade starts; carbon price is in 2012 $/tonne assuming 7% escalation; moderate recession assumes conditions consistent with current forward prices; and severe recession assumes five years of no load growth. 8 Gas Prices New Build Costs Carbon Year/Price Recession $0 $6.50 $1,300 Moderate 2014/$22 $7.30 $1,100 Moderate 2020/$22 $7.10 $1,100 Severe 2014/$22 $7.30 $1,500 Moderate 2012/$12 $8.60 $1,500 Moderate We look at fundamental value creation under a wide range of future commodity price scenarios and our analysis suggests $1-3 billion, possibly more Coal Prices $11.00 $20.00 $20.00 $20.00 $11.00

9 Without Premium 0 1,000 3,000 2,000 With Premium Conservative DCF Estimate Replacement Costs NRG Stock Value NRG Long-Term Value 975 1,350 2,050 3,000+ Price per Kilowatt Comparison for Texas Baseload Generation Exelon Unlocks NRG Value Less than 45% of replacement value Even with premium, purchase price is 66% of conservative long-term DCF value subtracting value of other NRG assets from NRG enterprise value based on October 17 th close. $/KW values are for 5,325 MW of Texas baseload which includes Parish coal, Limestone, and STP; values implied by NRG stock price are determined by

10 World Class Nuclear & Fossil Operations High performing nuclear plant • Top quartile capacity factor – 94.9% • Large, well-maintained, relatively young units Fossil fleet • Half of >500 MW coal units are top quartile capacity factor • 90% of coal fleet lower-cost PRB and lignite NRG Premier U.S. nuclear fleet • Best fleet capacity factor ~ 94% • Lowest fleet production costs ~ $15 /MWh • Shortest fleet average refueling outage duration – 24 days • Strong reputation for performance Exelon

11 <1% <1% 6% Coal Exelon ~150,000 GWh Pro Forma Exelon ~198,000 GWh Nuclear PRB & Lignite Coal Other Coal Gas/Oil Hydro/Other 2009 Historical Forward Coal Prices Combined Entity Will Continue to Benefit from Low Cost, Low Volatility Fuel Sources 0.00 1.00 2.00 3.00 4.00 5.00 6.00 Powder River Basin Northern Appalachian Central Appalachian Production Costs 0 2 4 6 8 10 12 2000 2001 2002 2003 2004 2005 2006 2007 Nuclear Gas Coal Petroleum 93% Nuclear 1% 3% 75% Nuclear 15% PRB & Lignite Coal 6% Other Coal (1) Based on 2007 data, does not include ~38,000 GWh of Exelon Purchased Power. Q1 2007 Q2 2007 Q3 2007 Q4 2007 Q1 2008 Q2 2008 Q3 2008 Powder River Basin and lignite coal supply (90% of NRG’s coal) provides low-sulfur at a relatively stable price as compared to northern and central Appalachian coal mines. Combined fleet will continue to be predominantly low-cost fuel. 1 1

0 50 100 150 50 100 150 200 250 2006 Electricity Generated (GWh, in thousands) NRG TVA AEP Duke FPL Southern Exelon + NRG Entergy Exelon Dominion Progress FirstEnergy Bubble size represents carbon intensity, expressed in terms of metric tons of CO2 per MWh generated SOURCE: EIA and EPA data as compiled by NRDC CO2 Emissions of Largest US Electricity Generators Largest Fleet, 2nd Lowest Carbon Intensity Top Generators by CO2 Intensity 10 9 8 7 6 5 4 3 2 1 12 Exelon 2020 principles will be applied to the combined fleet AEP NRG Southern Duke FirstEnergy TVA Progress Dominion FPL Exelon + NRG Entergy Exelon 0.83 0.80 0.74 0.66 0.64 0.64 0.57 0.50 0.35 0.31 0.26 0.07

Financing Plan Considerations • Negotiated acquisition of NRG would require refinancing of only ~$4B of NRG debt and other credit facilities – Under a negotiated deal with NRG, $4.7B of NRG bonds could remain in place with no change in terms, but with substantially improved credit metrics for those bondholders – Exelon's relationships with many of NRG's banks should facilitate arrangements for new credit facilities – Financing commitments are well underway for refinancing • The NRG direct lien program for power marketing could be left in place 13

14 Premier Balance Sheet and Credit Metrics Committed to returning Exelon Generation’s senior unsecured debt to strong investment grade within the next 3 years Targeting stronger credit metrics for the combined entity -- 25 - 30% FFO/debt Pay down debt plan will include: NRG balance sheet cash, asset sale proceeds, free cash flow Exelon NRG Today 2011 Credit Rating: BBB FFO / Debt: 25-30% Combined Entity Targets Credit Rating: BBB- FFO / Debt: 26% Credit Rating: B+ FFO / Debt: 18% 2 3 1 (1) Ratios exclude securitized debt. (2) Senior unsecured credit rating and FFO/Debt as of 10/31/08.  Reflects S&P updated guidelines, which include imputed debt and interest related to purchase power agreements, unfunded pension and other postretirement benefits obligations, capital adequacy for energy trading, operating lease obligations and other off-balance sheet data.  (3) From Standard & Poor’s 8/28/08 CreditStats: Independent Power Producers & Energy Traders – U.S.

15 Principal Regulatory Approvals and Expected Divestitures • Principal regulatory approvals: – Texas, New York, Pennsylvania, California state regulatory commissions – Hart-Scott-Rodino (DOJ/FTC) – FERC – NRC – Notice filing in Illinois • Limited market power issues – not expected to challenge transaction closing – Divestitures anticipated only in PJM and ERCOT – ~3,200 MWs of high heat rate gas and baseload coal plants  and ~1,200 MWs under contract – Model assumes $1 billion of proceeds from divestitures (after-tax) Regulatory hurdles are manageable 1 (1) Plants subject to divestiture are de minimus contributors to revenue and earnings.

16 Exelon More Than Meets the “Five Imperatives” Outlined by NRG on May 28, 2008 1. 1. 2. 2. 3. 3. 4. 4. 5. 5. NRG’s Stated Imperatives MUST accumulate generation at competitive cost This transaction accomplishes in one step what several transactions might have accomplished for NRG in these regards.  Given the current difficulty in accessing capital markets, it is unclear whether NRG would have the ability to meet this objective without Exelon. Exelon provides NRG stakeholders with broad trading expertise and sound power marketing and risk management practices.  Exelon’s significant experience in markets with locational prices is particularly relevant since ERCOT is moving to a PJM-type structure. Exelon’s breadth of operations and depth of service allows unparalleled access to customers, retail providers, and other sales channels. NRG stakeholders become part of the most diversified and competitive generation portfolio operating in 12 different states and 6 different regional transmission organizations. Deal provides NRG stakeholders with significant value and upside and a share of the largest unregulated generation fleet in the United States. MUST be geographically diversified in multiple markets MUST develop and expand our route to market through contracting with retail load providers, trading, direct sales, etc MUST have sophisticated ability to trade, procure, hedge, and originate for electricity and input fuels MUST develop depth and breadth in key markets, particularly across fuel types, transmission constraints and merit order Exelon Combination More than Meets These Imperatives

17 Exelon Key Messages Compelling Offer for NRG • Consistent with Exelon Protect and Grow Strategy • Earnings and cash accretion • Clear value creation • Meets NRG’s “Five Imperatives” Exelon Financial Outlook • 2009 operating guidance of $4.00 - $4.30/share • Managing costs and driving productivity • Significant uplift in 2011 - operating earnings of ~$5.00-$6.00/share (1) (1) Illustrative. Provided solely to illustrate possible future outcomes that are based on a number of different assumptions, all of which are subject to uncertainties and should not be relied upon as earnings guidance or a forecast of future results.

18 Appendix Additional Information regarding Offer for NRG

19 Pro Forma Exelon Combined company will have requisite scope, scale and financial strength to succeed in an increasingly volatile energy market Combination Will Result in Scope, Scale and Financial Strength (1) Reflects total assets (under GAAP) with no adjustments. Based upon 9/30/08 Form 10-Q. (2) Reflects Last Twelve Months EBITDA (Earnings before Income Taxes, Depreciation and Amortization) as of 9/30/08 with no adjustments. (3) Calculation of Enterprise Value = Market Capitalization (as of 10/31/08) + Total Debt (as of 6/30/08) + Preferred Securities (as of 6/30/08) + Minority Interest (as of 6/30/08) – Cash & Cash Equivalents (as of 6/30/08). Debt, Preferred Securities, Minority Interest and Cash & Cash Equivalents based upon 6/30/08 Form 10-Q. (4) Includes owned-and-contracted capacity after giving effect to planned divestitures after regulatory approvals. $0 $30 $50 $60 $40 $20 $70 $10 Southern Dominion FPL Duke First Energy Entergy $68,900 Combined assets (1) $9,400 LTM EBITDA (2) ($ in millions) $63,000 Enterprise value (3) ~51,000MWs Generating capacity (4) Pro Forma Quick Stats Market cap (as of 10/31/08) $41,200

Combination Enables Access to Attractive New Markets By RTO Combined   PJM 22,812 ERCOT 13,027 MISO 1,065 ISO NE 2,174 NYISO 3,960 CAL ISO 2,085 Contracted* 6,280 51,403 SERC 2,405 WECC 45 Total 53,853 By Fuel Type Combined Nuclear 18,144 Coal 8,986 Gas/Oil 18,801 Other 1,642 Contracted 6,280 *Contracted in various RTOs, mainly in PJM and ERCOT (1) Excludes international assets. Before any divestitures. 20 Geographically complementary asset base  Attractive new markets for Exelon (NY, NE, CA): declining reserve margins, supportive regulatory structures Predominantly located in competitive markets ERCOT portfolio will position Exelon to offer an array of products, capture value, and efficiently utilize credit 1 1 Exelon NRG

21 Nuclear Growth Opportunities • Texas offers nuclear growth platform • Potential for stretch power uprate (5-7%) on South Texas Project units 1 and 2 • Construction & Operating License and Loan Guarantee applications filed for both STP 3 and 4 and Victoria County • Exelon has the financial strength and discipline to investigate these opportunities • Strong balance sheet and credit metrics • Demonstrated track record of financial rigor • Nuclear depth and expertise • Options to build remain under evaluation; no commitment has yet been made

22 Exelon 2020 and NRG • Expand internal energy efficiency, SF6, vehicle, and supply chain initiatives to NRG portfolio • Offset a portion of NRG’s GHG emissions • Expand energy efficiency program offerings • Add capacity to existing nuclear units through uprates • Add new renewable generation • Add new gas-fired capacity • Continue to explore new nuclear • Address older/higher emitting coal and oil units • Invest in clean coal technology R&D Options to Evaluate:      Taking the next step in Exelon’s commitment to address climate change Offer more low carbon electricity in the marketplace Reduce emissions from coal/oil fired generation Help our customers and the communities we serve reduce their GHG emissions Reduce or offset our footprint by greening our operations Apply Elements of Exelon 2020 to NRG Expand the 2020 Plan

23 NRG is Best Investment Available 0% 4.0% 8.0% 12.0% 16.0% 0.0% 5.0% 10.0% 15.0% 20.0% 25.0% (10.0%) 0% 5.0% 20.0% EBITDA / EV Yield Earnings Yield Free Cash Flow Yield EXC Illustrative Utilities  NRG at Offer 2009E 2010E 7.9 10.2 11.8 10.6 8.1 11.4 11.9 10.7 IPPs EXC Illustrative Utilities  NRG at Offer IPPs EXC Illustrative Utilities  NRG at Offer IPPs 13.7 15.4 20.1 16.7 14.4 16.1 20.1 17.1 Source: FactSet. Prices as of 10/17/08, I/B/E/S estimates as of 10/31/08. EV = Enterprise Value (1) Illustrative Utilities include CMS, CNL, DPL, TE, WEC, WR. (2) IPPs include CPN, DYN, MIR, RRI. 4.3 (3.1) 11.2 11.6 5.2 (6.2) 14.2 12.3 15.0% 10.0% (5.0%) 1 2 2 2 1 1