Filed by Constellation Energy Group, Inc.

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.

Commission File No. 333-175162

On August 18, 2011, the following communication was distributed to Constellation Energy employees and posted on a company internal website dedicated to the merger with Exelon.

Exelon Constellation Energy8/2011

IN

August 30 and 31 will bring lots of buzz to Baltimore – the

city will be preparing to host its first Grand Prix event later

that week while our integration planning teams will be coming

together to kick off our design phase. Unlike the frenetic

energy and pace of the Grand Prix race which will span

several chaotic days, our design phase will be a thoughtful,

collaborative process which will take us close to the end of the

year. The Business Area Teams have spent several productive

months in the analysis phase and now that we have a better

understanding of how each company runs, we will work closely

with our leaders to meld these operations together into one

company that will best serve our customers.

Following the design phase kick-off meeting, we will

communicate outcomes, learnings and an updated merger

integration timeline. Thank you for your patience and continued

support.

A Note from Ron and Steve

TEGRATION

FORMATION

Expected Milestones

August September October November December January 2012

Oct 31 to Nov 10:

Maryland PSC hearings, each business day

Nov 29

Dec 1

Dec 5

Jan 5:

Maryland

PSC decision

deadline

- Maryland PSC

public comment

hearings

Q3: Expect to seek shareholder approval

Aug 3 Approved by Texas PUCT

Rules of the Road

While Exelon and Constellation work to

obtain necessary regulatory approvals

and to close the transaction, the

companies must operate as entirely

separate businesses. Employees must

treat one another as competitors in our

day-to-day work. This means we cannot

directly exchange competitively sensitive

information, and must be careful not to

do anything that lessens competition

between the companies or that would

lessen either entity’s ability to compete

were the transaction not to close. This is

an important and sometimes complicated

topic. If you have any questions, please

discuss with your supervisor or legal

counsel before action is taken.

Ron DeGregorio

Chief Integration Officer,

Exelon

Steve Woerner

Chief Integration Officer,

Constellation Energy

Feedback

IN is produced by the Corporate

Communications Groups of both Exelon

and Constellation.

Please direct questions and comments to:

Exelon employees:

IntegrationOffice@exeloncorp.com

Constellation employees:

IntegrationOffice@constellation.com

ComEd Timeline

INTEGRATION INFORMATION 8/18/2011

1900

1950

2000

Company History: ComEd

As a company, ComEd has a rich

100-year legacy of innovation that’s

helped northern Illinois develop

into the industrial powerhouse it is

today. As one of the largest utilities

in the United States, ComEd provides

service to approximately 3.8 million

customers, roughly 70 percent of

the state’s population. A great deal

has changed since ComEd opened

its doors in 1887, but one question

remains — and that question must be

asked daily: how can ComEd better

serve its customers? By striving to

answer this question, ComEd maintains

a strong commitment to being the

best electricity delivery and energy

information company.

1870s

Thomas Edison invents

incandescent light bulb

1892

Innovator and investor Sam

Insull appointed to run

Chicago Edison Company

1997

Deregulation of the electric

industry

1999

ComEd renews reliability

commitment after the

downtown Chicago blackouts

1978

Commonwealth Edison’s

nuclear generation capacity

surpasses its coal-fired

generation

1907

Due to increased demand

for electric lighting, Chicago

Edison and Commonwealth

Electric merge

2007

The industry transitions to a

fully competitive supply-side

market

1887

Chicago Edison Company created to

develop central incandescent light

business

1903

Establishment of Fisk generating

station

1960

Commonwealth Edison’s Dresden

Unit 1, the world’s first full-scale,

privately financed nuclear

power plant opens

1994

Commonwealth Edison undertakes

holding company reorganization,

with Unicom becoming its holding

company while the utility company

becomes rebranded as ComEd

1998

Unicom announces the sale of its fossil

fuel facilities

2000

Unicom and PECO merge to form

Exelon. Exelon begins trading on the

NYSE under the ticker symbol “EXC”

in October

2010

ComEd rolls out its new vision and

values framework

For more info, visit us online!

New Baltimore

Headquarters Update

Exelon employees can visit the

Merger Integration Site on the

Exelon intranet site.

Constellation employees can visit

the Merger Integration Site on

myConstellation.

In the previous two issues of IN, we

began to detail the process for selecting

a location for the new Baltimore

headquarters. In coming issues, we

will continue to outline the process

for selecting the new Baltimore

headquarters, preliminary results of

space program interviews and how

an employee engagement council will

be asked to participate in the process.

The team structure graphic shows the

initial make-up of the project team,

stakeholder representatives and their

respective focus areas. Additional subteam

members will be selected from

Exelon and Constellation as we move

forward in the process. Stay tuned for

future issues of IN with more information

on the site selection process.

Exelon Power

Headquartered in Kennett Square, Pa., Exelon Power is the business unit responsible for managing, operating, and maintaining Exelon

Generation’s portfolio of fossil and renewable fleet of generating assets. Exelon Power’s fleet currently consists of fossil (oil, natural gas

and coal), landfill gas and hydroelectric units, and wind and solar projects that are capable of generating more than 8,000 megawatts

(MW). Exelon Power’s assets are located in Pennsylvania, Maryland, Illinois, Texas, Massachusetts, Oregon, Idaho, Kansas, Minnesota,

Michigan, and Missouri, with a strong presence in the 13-state PJM Interconnection. The diversity of Exelon Power’s portfolio allows the

company to be competitive in the deregulated power market during the intermediate seasons and peak demand periods.

The clean and renewable energy produced for the energy market by Exelon Power’s fleet is a critical element of Exelon 2020: a lowcarbon

roadmap. The goal of Exelon 2020 is to eliminate the equivalent of the company’s 2001 carbon footprint, or 15 million metric

tons of greenhouse gas emissions, by 2020. Read more about Exelon Power’s clean energy fleet—Hydro, Solar, Wind

Constellation Power Generation

Constellation Power Generation (CPG) is the business that operates and manages Constellation Energy’s fleet of 32 non-nuclear power

plants, which generate nearly 10,000 MW from fossil fuel and renewable energy sources. These plants and their employees support

Constellation’s merchant energy business in key regions across the U.S and in Canada. CPG’s fossil and renewable plants include more

than 3,500 MW of fossil fuel-fired capacity in the Baltimore metropolitan area, a nearly 3,000 MW fleet of natural gas and oil facilities in

Boston, 1,100 MW of natural gas-fired generation in Texas, and ownership interest in clean energy facilities with fuel sources that include

solar, hydro, biomass and wind. Included in that portfolio is Criterion Wind, Maryland’s first-ever wind project, which was built by CPG

and began operating in late 2010.

CPG includes nearly 1,200 employees in both operations and support of power generating facilities, all focused on the group’s

commitment to safety and environmental stewardship. CPG currently has 15 plants across the country that have operated for between

two and 17 consecutive years without a lost time work case. In addition, in 2009, CPG’s ACE Cogeneration plant in Trona, Calif., was

recognized for its outstanding safety program by achieving STAR status under California’s Division of Occupational Safety and Health.

Read more about CPG’s clean energy fleet here.

Focus on Generation: Fossil and Renewables

INTEGRATION INFORMATION 8/18/2011

New Baltimore Headquarters Project Team Structure

Senior executives who represent the area’s

perspective from an enterprise point

of view, providing guidance on crossenterprise

considerations. Corporate/Legal

Affairs, Finance, Human Resources and

Communications are represented.

STEERING COMMITTEE:

Employees asked by their leadership to

participate as ambassadors for the project,

help deliver new headquarters related

messages to other employees, and provide

feedback into certain design elements, such

as furniture, branding, etc. This team will be

developed once the merger closes.

EMPLOYEE ENGAGEMENT COUNCIL:

Dedicated project team members with a

day-to-day, hands-on project role for the

specific function. Project sub-teams include

architects, project managers, space planners,

construction advisors, real estate advisors and

others as needed.

PROJECT DELIVERY TEAM:

Functional area representatives who represent

the occupant/employee perspective and

act as the ‘change leaders’ and liaison to

the functional area employees. Stakeholder

sub-teams include Commercial, Corporate

(IT, Finance, Shared Services, Security), and

Renewable Energy Development.

STAKEHOLDER TEAM:

Cautionary Statements Regarding Forward-Looking Information

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. 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 June 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 preliminary joint proxy statement/prospectus included

in Amendment No. 1 to the Registration Statement on Form S-4 that Exelon filed with the SEC on August 17, 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

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, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to

registration or qualification under the securities laws of any such jurisdiction. On August 17, 2011, Exelon filed with the SEC Amendment No.

1 to its Registration Statement on Form S-4 that included a preliminary joint proxy statement/prospectus and other relevant documents

to be mailed by Exelon and Constellation to their respective security holders in connection with the proposed merger of Exelon and

Constellation. These materials are not yet final and may be amended. WE URGE INVESTORS AND SECURITY HOLDERS TO READ

THE PRELIMINARY JOINT PROXY STATEMENT/PROSPECTUS AND THE DEFINITIVE JOINT PROXY STATEMENT/PROSPECTUS AND

ANY OTHER RELEVANT DOCUMENTS WHEN THEY BECOME AVAILABLE, BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT

INFORMATION about Exelon, Constellation and the proposed merger. Investors and security holders will be able to obtain these materials

(when they are available) and other documents filed with the SEC free of charge at the SEC’s website, www.sec.gov. In addition, a copy

of the preliminary joint proxy statement/prospectus and definitive joint proxy statement/prospectus (when it becomes available) 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. Investors and

security holders may also read and copy any reports, statements and other information filed by Exelon, or Constellation, with the SEC,

at the SEC public reference room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 or visit the SEC’s

website for further information on its public reference room.

Participants in the Merger Solicitation

Exelon, Constellation, and their respective directors, executive officers and certain other members of management and employees 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 proxy statement filed with the SEC by Exelon on March 24, 2011 in connection with its 2011 annual

meeting of shareholders, and information regarding Constellation’s directors and executive officers is available in its proxy statement filed

with the SEC by Constellation on April 15, 2011 in connection with its 2011 annual meeting of shareholders. Other information regarding the

participants in the proxy solicitation and a description of their direct and indirect interests, by security holdings or otherwise, is contained in

the preliminary joint proxy statement/prospectus and will be contained in the definitive joint proxy statement/prospectus.

© Exelon Corporation, 2011

© Constellation Energy Group, 2011

INTEGRATION INFORMATION 8/18/2011

Cautionary Statements Regarding Forward-Looking Information

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. 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 June 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 preliminary joint proxy statement/prospectus included in Amendment No. 1 to the Registration Statement on Form S-4 that Exelon filed with the SEC on August 17, 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

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, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. On August 17, 2011, Exelon filed with the SEC Amendment No. 1 to its Registration Statement on Form S-4 that included a preliminary joint proxy statement/prospectus and other relevant documents to be mailed by Exelon and Constellation to their respective security holders in connection with the proposed merger of Exelon and Constellation. These materials are not yet final and may be amended. WE URGE INVESTORS AND SECURITY HOLDERS TO READ THE PRELIMINARY JOINT PROXY STATEMENT/PROSPECTUS AND THE DEFINITIVE JOINT PROXY STATEMENT/PROSPECTUS AND ANY OTHER RELEVANT DOCUMENTS WHEN THEY BECOME AVAILABLE, BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION about Exelon, Constellation and the proposed merger. Investors and security holders will be able to obtain these materials (when they are available) and other documents filed with the SEC free of charge at the SEC’s website, www.sec.gov. In addition, a copy of the preliminary joint proxy statement/prospectus and definitive joint proxy statement/prospectus (when it becomes available) 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. Investors and security holders may also read and copy any

reports, statements and other information filed by Exelon, or Constellation, with the SEC, at the SEC public reference room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 or visit the SEC’s website for further information on its public reference room.

Participants in the Merger Solicitation

Exelon, Constellation, and their respective directors, executive officers and certain other members of management and employees 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 proxy statement filed with the SEC by Exelon on March 24, 2011 in connection with its 2011 annual meeting of shareholders, and information regarding Constellation’s directors and executive officers is available in its proxy statement filed with the SEC by Constellation on April 15, 2011 in connection with its 2011 annual meeting of shareholders. Other information regarding the participants in the proxy solicitation and a description of their direct and indirect interests, by security holdings or otherwise, is contained in the preliminary joint proxy statement/prospectus and will be contained in the definitive joint proxy statement/prospectus.

* * * * *