Filed by Exelon Corporation

Pursuant to Rule 425 under the Securities Act of 1933

and deemed filed pursuant to Rule 14a-12 of the Securities Exchange Act of 1934

Subject Company: Constellation Energy Group, Inc.

(Reg. No. 333-175162)

On November 7, 2011, Exelon began to use the following slides concerning the proposed merger and other information with investors at the Edison Electric Institute Financial Conference:

Exelon and Constellation Energy: Merger and Company Update Edison Electric Institute Financial Conference November 7-8, 2011

Cautionary Statements Regarding Forward-Looking Information 2 Except for the historical information contained herein, certain of the matters discussed in this communication constitute “forward-looking statements” within the meaning of the Securities Act of 1933 and the Securities Exchange Act of 1934, both as amended by the Private Securities Litigation Reform Act of 1995. Words such as “may,” “will,” “anticipate,” “estimate,” “expect,” “project,” “intend,” “plan,” “believe,” “target,” “forecast,” and words and terms of similar substance used in connection with any discussion of future plans, actions, or events identify forward-looking statements. These forward- looking statements include, but are not limited to, statements regarding benefits of the proposed merger of Exelon Corporation (Exelon) and Constellation Energy Group, Inc. (Constellation), integration plans and expected synergies, the expected timing of completion of the transaction, anticipated future financial and operating performance and results, including estimates for growth. These statements are based on the current expectations of management of Exelon and Constellation, as applicable. There are a number of risks and uncertainties that could cause actual results to differ materially from the forward-looking statements included in this communication regarding the proposed merger. For example, (1) the companies may be unable to obtain shareholder approvals required for the merger; (2) the companies may be unable to obtain regulatory approvals required for the merger, or required regulatory approvals may delay the merger or result in the imposition of conditions that could have a material adverse effect on the combined company or cause the companies to abandon the merger; (3) conditions to the closing of the merger may not be satisfied; (4) an unsolicited offer of another company to acquire assets or capital stock of Exelon or Constellation could interfere with the merger; (5) problems may arise in successfully integrating the businesses of the companies, which may result in the combined company not operating as effectively and efficiently as expected; (6) the combined company may be unable to achieve cost-cutting synergies or it may take longer than expected to achieve those synergies; (7) the merger may involve unexpected costs, unexpected liabilities or unexpected delays, or the effects of purchase accounting may be different from the companies’ expectations; (8) the credit ratings of the combined company or its subsidiaries may be different from what the companies expect; (9) the businesses of the companies may suffer as a result of uncertainty surrounding the merger; (10) the companies may not realize the values expected to be obtained for properties expected or required to be divested; (11) the industry may be subject to future regulatory or legislative actions that could adversely affect the companies; and (12) the companies may be adversely affected by other economic, business, and/or competitive factors. Other unknown or unpredictable factors could also have material adverse effects on future results, performance or achievements of Exelon, Constellation or the combined company.

Cautionary Statements Regarding Forward-Looking Information (Continued) 3 Discussions of some of these other important factors and assumptions are contained in Exelon’s and Constellation’s respective filings with the Securities and Exchange Commission (SEC), and available at the SEC’s website at www.sec.gov, including: (1)  Exelon’s 2010 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 18; (2)  Exelon’s Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2011 in (a) Part II, Other Information, ITEM 1A. Risk Factors, (b) Part 1, Financial Information, ITEM 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations and (c) Part I, Financial Information, ITEM 1. Financial Statements: Note 13; (3)  Constellation’s 2010 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 12; and (4) Constellation’s Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2011 in (a) Part II, Other Information, ITEM 1A. Risk Factors and ITEM 5. Other Information, (b) Part I, Financial Information, ITEM 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations and (c) Part I, Financial Information, ITEM 1. Financial Statements: Notes to Consolidated Financial Statements, Commitments and Contingencies. These risks, as well as other risks associated with the proposed merger, are more fully discussed in the definitive joint proxy statement/prospectus included in the Registration Statement on Form S-4 that Exelon filed with the SEC and that the SEC declared effective on October 11, 2011 in connection with the proposed merger.  In light of these risks, uncertainties, assumptions and factors, the forward-looking events discussed in this communication may not occur. Readers are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this communication. Neither Exelon nor Constellation undertake any obligation to publicly release any revision to its forward-looking statements to reflect events or circumstances after the date of this communication. Additional Information and Where to Find it In connection with the proposed merger between Exelon and Constellation, Exelon filed with the SEC a Registration Statement on Form S-4 that included the definitive joint proxy statement/prospectus. The Registration Statement was declared effective by the SEC on October 11, 2011. Exelon and Constellation mailed the definitive joint proxy statement/prospectus to their respective security holders on or about October 12, 2011. WE URGE INVESTORS AND SECURITY HOLDERS TO READ THE DEFINITIVE JOINT PROXY STATEMENT/PROSPECTUS AND ANY OTHER RELEVANT DOCUMENTS FILED WITH THE SEC, BECAUSE THEY CONTAIN IMPORTANT INFORMATION about Exelon, Constellation and the proposed merger. Investors and security holders may obtain copies of all documents filed with the SEC free of charge at the SEC's website, www.sec.gov. In addition, a copy of the definitive joint proxy statement/prospectus may be obtained free of charge from Exelon Corporation, Investor Relations, 10 South Dearborn Street, P.O. Box 805398, Chicago, Illinois 60680-5398, or from Constellation Energy Group, Inc., Investor Relations, 100 Constellation Way, Suite 600C, Baltimore, MD 21202.

4 Compelling Merger Rationale Creates the leading competitive energy provider in the U.S. Matches Exelon’s clean generation fleet with Constellation’s customer-facing leading retail and wholesale platform Creates economies of scale through expansion across the value chain Strategic Benefits Financial Benefits Diversifies generation portfolio across  regions Adds clean generation to the portfolio Enhances margins in the competitive portfolio Competitive Portfolio Earnings and cash flow accretive Dividend uplift for Constellation shareholders Continued upside to power market recovery Strong balance sheet for combined company Utility Benefits Maintains a regulated earnings profile with three large urban utilities Enables operational enhancements from sharing of best practices across utilities Transaction creates incremental strategic and financial value aligned with both companies’ existing goals

5 Merger Appeals to Key Stakeholders and Governments  (1)  Based on the 30-day average Exelon and Constellation closing stock prices as of April 26, 2011. Stakeholder Commitments & Benefits Customers $100 one -time credit for BGE residential customers Direct benefit from merger synergies at the utilities Opportunities for operational improvements through sharing of utilities’ best practices $15 million for various programs with direct benefits to BGE customers Investors Upfront premium of 18.5% (1) to CEG shareholders Dividend accretion of 103% post-close for CEG shareholders EPS accretion of >5% in 2013 Earnings upside to power market recovery Strong credit profile maintained for combined company State of Maryland and City of Baltimore Maintains a large employee presence and platform for growth in Maryland New LEED-certified headquarters for wholesale, retail and renewable energy development business in Baltimore BGE to maintain independent operations and remain headquartered in Baltimore 25 MWs of renewable energy development in MD $4 million to support EmPower Maryland Energy Efficiency Act Charitable contributions maintained at current levels for at least 10 years after the merger closes

6 Enhanced Maryland Proposal Our additional commitments address a number of key stakeholder concerns Intervenor Concerns Key Exelon/Constellation Additional Commitments Additional Customer Benefits Added flexibility for Maryland PSC to determine use of $15 million offered for programs directly benefiting BGE customers Ring-Fencing No corporate reorganization under certain defined circumstances relating to RF HoldCo, BGE or Exelon Energy Delivery Company without prior Commission approval Obtain a new non-consolidation opinion to ensure the effectiveness of BGE ring- fencing No requests for modification of BGE ring-fencing for 3 years Financial Regular reporting on credit ratings and metrics of BGE to Maryland PSC Specific commitments regarding the level of BGE capital and O&M expenditures in 2012 and 2013 Report comparative pre- and post-merger shared services costs to PSC Corporate Governance BGE’s CEO will be a member of Exelon Management’s Executive Committee Executive Committee will meet periodically in Baltimore Service and Operation Commitment to meet existing BGE supplier diversity requirements Provide assessment of BGE CAIDI (outage duration) performance within 12 months after the merger closes Market Power In addition to 2,648 MW of identified plant divestitures, comply with settlement terms with PJM Market Monitor restricting buyers of divested plants and imposing other behavioral commitments

7 Strong Proposal to Address Market Power The companies have offered a comprehensive, robust mitigation package C.P. Crane    399 MW Brandon Shores  1,273 MW H.A. Wagner       976 MW Note: Assets to be divested – Brandon Shores (Coal), H.A. Wagner (Coal/Oil/Gas) and C.P. Crane (Oil/Coal). Analyzed market power considerations and proposed mitigation plan to address market concentration concerns Proposed comprehensive mitigation plan to address market concentration in PJM in initial application, including: • Physical sale of 3 baseload generation facilities totaling 2,648 MW • Additional sale of 500 MW via contracts to mitigate temporary market power issues Filed with FERC and Maryland PSC on October 11, 2011 No change to assets identified in original proposal Additional commitment not to sell plants to certain identified PJM generators Additional assurances on how we will bid units in PJM energy and capacity markets Future retirement of units will be conditioned on meeting specified requirements Proactive divestiture proposal Settlement with PJM Independent  Market Monitor (IMM)

8 Note: Data as of 9/30/11.  Exelon solar addition MW based on alternating current (AC); Constellation solar additions (in MW) based on direct current (DC). (1)    Generation capacity net of physical market mitigation assumed to be 2,648 MW consisting of Brandon Shores (1,273 MW), H.A. Wagner (976 MW) and C.P. Crane (399 MW). (2)    Electric load includes all booked 2011E competitive retail and wholesale sales, including index products. Exelon load does not include the ComEd swap (~26 TWh). Gas load includes all booked and forecasted 2011E competitive retail sales as of 9/30/11. Reserves (gas) 266 bcf Owned Generating Capacity 35 GWs (1) Electric Transmission 7,350 miles Electric & Gas Dist. 6.6 million customers Retail & Wholesale Volumes (2) (Electric & Gas) ~167 TWh, 372 bcf Notable Generation Acquired or Under Development in 2011 Exelon Additions 720 MW Wolf Hollow CCGT (TX) 230 MW Antelope Valley Solar Ranch One (CA) 230 MW Michigan Wind Projects (MI) Constellation Additions 2,950 MW Boston Generating gas fleet 30.4 MW Sacramento Municipal Utility District Solar (CA) 16.1 MW Maryland Generating Clean Horizons Solar (MD) 7.8 MW Vineland Municipal Electric Utility Solar (NJ) 5.4 MW Toys “R” Us Solar (NJ) 5.2 MW Johnson Matthey, West Deptford Solar (NJ) 5.0 MW U.S. State Department Solar (NJ) Transaction creates the largest – and growing – competitive energy company in the U.S. Scale, Scope and Flexibility Across the Value Chain Upstream Downstream

Well Positioned for Evolving Regulatory Requirements (1) Total owned generation capacity as of 9/30/2011 for Exelon and Constellation, net of physical market mitigation assumed to be 2,648 MW. (2) Coal capacity shown above includes Eddystone 2 (309 MW) to be retired on 6/1/2012. (3) Oil capacity shown above includes Cromby 2 (201 MW) to be retired on 12/31/2011. (4) Pending approval of owner group. A clean and diverse portfolio that is well positioned for environmental upside from EPA regulations 9 Total Generation Capacity (1) : 35,327 MW 5% Wind/Solar/Other 3% Gas Hydro Oil (3) Nuclear 54% 6% Coal (2) 5% Cleanest large merchant generation portfolio in the nation Less than 5% of combined generation capacity will require capital expenditures to comply with Air Toxic rules - Approx. $200 million of CapEx, majority of which is at Conemaugh (4) (Exelon and Constellation ownership share ~31%) Low-cost generation capacity provides unparalleled leverage to rising commodity prices  Incremental 500 MW of coal and oil capacity to be retired by middle of next year Combined Company Portfolio 27%

10 Texas Generation Portfolio Is Well Suited to Serve Load ERCOT Generation Capacity – MW (1) 5,311 CEG Intermediate 1,839 EXC Intermediate 2,210 Exelon Peaking 1,262 (1) Generation and capacity for Exelon and Constellation includes owned and contracted units, less any PPAs or tolls sold, as of 09/30/2011. Exelon wind assets in Texas (open or hedged) are not included in the capacity shown above. Constellation capacity includes 517 MWs under a contract that expires in December 2011. The combined generation portfolio will enhance the hedging capability for managing load positions in Texas Premium Location – A sizeable generation Hedging Flexibility – Leverage strong asset Strong Asset Mix – Intermediate and peaking base and utilize market-based hedging instruments to effectively manage load- following obligations position close to large load pockets in Dallas and Houston generation assets are effectively call options at various heat rates that benefit from price volatility

11 We will continue to use a well-defined hedging strategy to carefully balance risk management and value creation Increase the amount of generation hedged over time, leaving some open generation length Exhibit flexibility in timing and type of sales executed based on market expectations Select products and markets that optimize the value of the generation portfolio Integrate hedging policy with financial planning process to protect investment- grade credit rating Wholesale and Retail Businesses Grow our generation to load strategy in multiple regions of the country by identifying attractive investments and markets Expand product offerings to customers in regions we serve Growing the Portfolio Growing the Portfolio Hedging Program Characteristics Hedging Program Characteristics

Transaction Maintains Solid Financial Position Achievable Synergies Annual run rate BGE 8% ComEd & PECO 29% Unregulated Businesses 63% Year 4 $310 Year 3 Year 2 Year 1 $200 Annual O&M Expense Savings (1) (in $MM) 12 Lower Liquidity Requirements Existing liquidity (ex-utilities) Pro-forma liquidity $10.3 Reduction in existing liquidity (in $B) 5-Year Total Synergies Allocation (2) Maintaining Strong Investment Grade Ratings (3) Moody’s Credit Ratings S&P Credit Ratings Fitch Credit Ratings Exelon Baa1 BBB- BBB+ ComEd Baa1 A- BBB+ PECO A1 A- A Generation A3 BBB BBB+ Constellation Baa3 BBB- BBB- BGE Baa2 BBB+ BBB+ $3-$4 -39% $6.3 - $7.3 Pro-Forma $6.1 Exelon $4.2 Constellation Annual cost savings of $35M-$45M (1)  Before total costs to achieve of ~$650M primarily attributable to employee-related costs and transaction costs. (2)  Source: DeGregorio testimony filed with Maryland PSC on May 25, 2011. (3)  Ratings as of November 1, 2011.  Represents senior unsecured ratings of Exelon, Generation, Constellation and BGE and senior secured ratings for ComEd and PECO.  S&P and Fitch affirmed all Exelon ratings upon announcement of merger. Moody’s affirmed  the ratings of ComEd and PECO and placed the ratings of Exelon and Generation on review for downgrade. S&P and Moody’s placed Constellation on credit watch positive and  affirmed BGE ratings.  Fitch affirmed Constellation and BGE ratings upon announcement.

13 Phased Approach to Designing the Future  Our past experience with successful integration and our phased approach to integrating Exelon and Constellation will enable the realization of merger benefits Success is defined by: Closing the transaction in early 2012 Maintaining consistent and reliable operations Capturing value and meeting synergy targets Meeting commitments to stakeholders, regulators and governments Acting as one to build an integrated enterprise that is positioned for continued growth August – December Begins post-close Completed  in August Begins in November

Exelon & Constellation Energy Appendix

15 Merger Approvals Process on Schedule     (as of 11/1/11) Note: The Department of Public Utilities in Massachusetts concluded on September 26, 2011 that it does not have jurisdiction over the merger. Stakeholder Status of Key Milestones Approved Texas PUC (Case No. 39413) Filed for approval with the Public Utility Commission of Texas on May 17, 2011 Approval received on August 3, 2011 Securities and Exchange Commission (SEC) (File No. 333-175162) Joint proxy statement declared effective on October 11, 2011 Shareholder Approval Proxies mailed to shareholders of record at October 7, 2011 Shareholder meetings set for November 17, 2011 New York PSC (Case No. 11–E–0245) Filed with the New York Public Service Commission on  May 17, 2011 seeking a declaratory order confirming that a Commission review is not required Decision expected in Q4 2011 Department of Justice (DOJ) antitrust laws and certified compliance with second request Clearance expected by January 2012 Federal Energy Regulatory Commission (FERC) (Docket No. EC 11-83) Filed merger approval application and related filings on May 20, 2011, which Settlement agreement filed with PJM Market Monitor on October 11, 2011 Order expected by November 16, 2011 (end of statutory period) Nuclear Regulatory Commission (Docket Nos. 50-317, 50-318, 50-220, 50-410, 50-244, 72-8, 72-67) Filed for indirect transfer of Constellation Energy licenses on May 12, 2011 Order expected by January 2012 Maryland PSC (Case No. 9271) Filed for approval with the Maryland Public Service Commission on May 25, 2011 Evidentiary hearings begin October 31, 2011 Order expected by January 5, 2012 Submitted Hart-Scott-Rodino filing on May 31, 2011 for review under U.S. assesses market power-related issues

16 Maryland PSC Review Schedule (Case No. 9271) Significant Events Date of Event Filing of Application May 25, 2011 Intervention Deadline June 24, 2011 Prehearing Conference June 28, 2011 Filing of Staff, Office of People Counsel and Intervenor Testimony September 16, 2011* Filing of Rebuttal Testimony October 12, 2011* Filing of Surrebuttal Testimony October 26, 2011 Status Conference October 28, 2011 Evidentiary Hearings October 31, 2011 - November 18, 2011 Public Comment Hearings November 29, December 1 & December 5, 2011 Filing of Initial Briefs December 5, 2011 Filing of Reply Briefs December 19, 2011 Decision Deadline January 5, 2012 * Initial intervenor testimony with respect to market power was due on September 23   for all parties except for the Independent Market Monitor and rebuttal testimony with respect to market power was due on October 17    . rd th

Portfolio Matches Generation with Load in Key Competitive Markets MISO (TWh) PJM (1) (TWh) South (2) (TWh) ISO-NE & NY ISO (3) (TWh) West (4) (TWh) The combination establishes an industry-leading platform with regional diversification of the generation fleet and customer-facing load business Note: Data for Exelon and Constellation represents available expected generation (owned and contracted) and booked electric sales for 2011 as of 9/30/11. Expected generation is adjusted for assets that have long term PPAs sold by Exelon or Constellation, including but not limited to wind and South assets. Exelon load doesn’t include the ComEd swap (~26 TWh). Index load, which is a pass through load product with no price or volumetric risk to the seller, is not included in the load estimate. (1) Constellation generation includes output from Brandon Shores, C.P. Crane and H.A. Wagner (total generation ~8.5 TWh). (2) Represents load and generation in ERCOT, SERC and SPP. (3) Constellation load includes ~0.7 TWh of load served in Ontario. (4) Constellation generation includes ~0.4 TWh of generation in Alberta. Load 75.1 42.0 33.1 Generation 175.6 29.8 145.8 Constellation Exelon 5.7 Load 5.1 0.6 Generation 8.6 8.6 18.5 Load 30.3 Generation 26.2 7.7 1.9 Load Generation 0.6 Load 29.2 Generation 32.1 32.1 29.2 17

Manageable Debt Maturities Debt Maturity Profile (2012-2020) EXC EXC EXC Exelon 1,652 1,686 1,589 ExGen PECO ComEd Exelon BGE Constellation ~70% of 2012 – 2016 debt maturities consist of regulated utility debt (in $M) 18 Weighted Average Cost of Debt (2) Exelon 5.2% ComEd 5.4% PECO 5.5% ExGen 5.5% Constellation 6.2% BGE 6.3% 152 552 74 552 (1) 2020 550 550 2019 602 600 2018 1,342 500 840 2017 1,261 702 516 41 2016 1,117 665 379 2015 260 800 75 2014 500 250 617 70 2013 1,020 300 252 467 2012 1,001 375 450 2 2 2 173 3 2 (1) Debt maturity schedule and weighted average cost of debt as of 9/30/11.  Amounts do not include fair value swaps at Constellation. BGE debt balances include annual transition bond payments from 2012 – 2017. (2) Weighted average cost of debt excludes any benefits for interest rate swaps. Utilities’ weighted average cost of debt includes debt amortization costs.

19 Exelon Dividend Exelon’s Board of Directors approved a contingent stub dividend for Exelon shareholders of $0.00571/share per day for Q1 2012 in anticipation of the merger close ($0.525/share for the quarter) Stub dividend declaration ensures that Exelon shareholders continue to receive all dividends at the current $2.10 per share annualized rate Pre- and post-close stub dividends must be declared separately to account for Constellation shareholders becoming Exelon shareholders at merger close Assuming a February 1, 2012 close for illustrative purposes only: $0.525 Current Exelon shareholders will continue to receive a total dividend of $0.525 per quarter Record Date Payment Date Per Share Amount 11/15/2011 12/09/2011 Regular Dividend $0.525 1/31/2012 3/1/2012 Pre-close Stub Dividend $0.440 2/15/2012 3/09/2012 Post-close Stub Dividend $0.085 5/15/2012 6/09/2012 Regular Dividend $0.525 (1) (1) (2) (1) Assuming a 2/1/2012 merger close; for Exelon shareholders, Q1 2012 dividend will be based on a per diem rate of $0.00571 ($0.525 divided by 92 days). (2) Future dividend, following the stub dividend, is subject to approval by the Board of Directors.

20 Constellation Dividend Record Date Payment Date Per Share Amount 12/12/2011 1/03/2012 Regular CEG Dividend $0.24 1/31/2012 3/1/2012 Pre-close CEG Stub Dividend (1) $0.132 2/15/2012 3/09/2012 Post-close EXC Stub Dividend (1) $0.085 5/15/2012 6/09/2012 Regular EXC Dividend (2) $0.525 Constellation Energy’s Board of Directors approved a contingent stub dividend for Constellation shareholders of $0.00264/share per day for Q1 2012 in anticipation of merger close Stub dividend declaration ensures that Constellation shareholders continue to receive their existing quarterly dividend rate prior to the merger, and benefit from the Exelon annualized dividend rate ($2.10 per share) beginning on the day the merger closes Pre- and post-close stub dividends must be declared separately to account for Constellation shareholders becoming Exelon shareholders at merger close Constellation shareholders will receive the Exelon dividend rate upon merger close (1) Assuming a 2/1/2012 merger close, Q1 2012 dividend will be based on a per diem rate of $0.00264 ($0.24 divided by 91 days). Post-close  Exelon Q1 2012  stub dividend will be based on a per diem rate of $0.00571. (2) Assuming a 2/1/2012 merger close, Constellation shareholders will start receiving the full quarterly Exelon dividend of $0.525 per share in Q2 2012. Future dividend, following the stub dividend, is subject to approval by the Board of Directors. Assuming a February 1, 2012 close for illustrative purposes only: