Document:

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                                                                 EXHIBIT 10.15

                           NON-COMPETITION AGREEMENT

         NON-COMPETITION AGREEMENT, dated as of November 5, 1999, between ORION
POWER HOLDINGS, INC., a Delaware corporation (the "Company") and TOKYO ELECTRIC
POWER COMPANY INTERNATIONAL, B.V., a corporation organized under the laws of
the Netherlands ("TEPCO International").

                                   WITNESSETH

         WHEREAS, GS CAPITAL PARTNERS II, L.P., a Delaware limited partnership
("GSCP"), and CONSTELLATION POWER SOURCE, INC., a Delaware corporation
("Constellation"), as of March 10, 1998, caused the formation of the Company
and entered into a Stockholders' Agreement relating thereto (the "Original
Stockholders' Agreement");

         WHEREAS, the Company has been formed for the purpose of investing in
and managing the operations of electric generating assets in the United States
and Canada (the "Portfolio Assets");

         WHEREAS, as of June 25, 1999, the Company, GSCP and Constellation
amended and restated the Original Stockholders' Agreement in its entirety (the
"First Amended and Restated Stockholders' Agreement");

         WHEREAS, as of September 29, 1999, and October 4, 1999 Mitsubishi
Corporation ("Mitsubishi") and TEPCO International, respectively entered into
Subscription Agreements pursuant to which the Company committed to issue, and
Mitsubishi and TEPCO International committed to purchase, 77,419.355 and
51,612.903 shares, respectively, of Common Stock at the price of $1,550.00 per
share, for an aggregate purchase price of $120,000,000.00 and $80,000,000.00,
respectively;

         WHEREAS, as of the date hereof, the Company, GSCP, Constellation,
Mitsubishi, TEPCO International and the other parties named therein amended and
restated the First Amended and Restated Stockholders' Agreement in its entirety
(the "Second Amended and Restated Stockholders' Agreement"); and

         WHEREAS, the parties hereto intend to establish terms pursuant to
which TEPCO International and any Affiliate of TEPCO International
(collectively, the "TEPCO International Group") may engage in the acquisition
of Facilities.

         NOW, THEREFORE, in consideration of the promises and of the mutual
commitments and obligations hereinafter set forth, the parties hereto hereby
agree as follows:

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         SECTION 1.  Definitions.  As used herein, the following terms shall
have the following meanings:

         "Auction" means the attempted sale of a Facility or Facilities
pursuant to which the owner of the Facility or Facilities has stated or
announced that it intends to have or is having discussions, for the purpose of
soliciting a bid or bids, with respect to such sale of the Facility or
Facilities, or interests therein with more than one potential buyer.

         "Affiliate" shall mean, with respect to any Person, any other Person
directly or indirectly controlling or controlled by or under direct or indirect
common control with such specified Person.

         "Facility" means an electric generating facility in the United States
or Canada that, at the time of any purchase or attempted purchase, is either
fully constructed or has, or has previously had, commercial operations.

         "Greenfield Project" means a project to construct a new electric
generating facility in the United States or Canada when the interest to be
acquired is acquired prior to one hundred thirty five (135) days after the date
of commercial operation.

         "IPO" means an underwritten offering or series of underwritten
offerings pursuant to which the common stock, par value $.01 per share ("Common
Stock") of the Company, becomes registered under Section 12 of the Securities
Exchange Act of 1934, as amended (the "Exchange Act") (a) in which either (i)
the Common Stock issued in such IPO constitutes at least 20% of the Common
Stock or (ii) the gross proceeds to the Company and any selling stockholders,
in the aggregate, is at least $75 million before deducting underwriting
discounts, commissions and offering expenses and (b) which results in the
Common Stock being held by at least 500 holders of record within the meaning of
Rule 12g5-1 under the Exchange Act.

         "Negotiated Transaction" shall have the meaning set forth in Section
4.

         "Person" means any individual, corporation, limited liability company,
limited or general partnership, joint venture, association, joint-stock
company, trust, unincorporated organization, other entity or government or any
agency or political subdivisions thereof.

         SECTION 2. Term. The term of this Agreement shall be from the date
hereof until the earlier to occur of (i) the closing of an IPO, (ii) six months
after the date on which all TEPCO International Group representatives or
nominees have ceased to hold any of the following positions of the Company:
director, observer, officer or employee, (iii) the liquidation of the Company,
and (iv) five years after the date hereof.

         SECTION 3. Auctions. With respect to a Facility which is the subject
of an Auction, the TEPCO International Group shall be prohibited from bidding,
and shall

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not bid, or take any steps with the seller of the Facility or any other third
party to materially further the acquisition of such Facility, or any interest
therein ("Acquisition Actions"), unless the Company provides the TEPCO
International Group with prior written notice that the TEPCO International
Group may take Acquisition Actions with respect to such Facility (the "Granting
Notice"). Any Granting Notice shall be given by the Company in the sole
discretion of the Company and under no circumstance shall the Company be under
an obligation to provide a Granting Notice. If the Company provides to the
TEPCO International Group a Granting Notice with respect to a Facility, the
TEPCO International Group may take any and all Acquisition Actions with respect
to such Facility. The Company may, but shall be under no obligation to, proceed
with Acquisition Actions with respect to a Facility for which it did not
provide a Granting Notice.

         SECTION 4. Negotiated Transactions. If the TEPCO International Group
wishes to take Acquisition Actions with respect to a Facility (the "Subject
Facility") which is not the subject of an Auction (any transaction, or
attempted transaction, to acquire any such Facility, or an interest therein, is
referred to as a "Negotiated Transaction"):

                    (i)      the TEPCO International Group shall provide, in
good faith, taking into account all relevant facts and circumstances, the
Company with written notice (a "Facility Notice") including (a) the identity of
the Subject Facility, (b) a statement that the TEPCO International Group,
subject to this Section 4, intends to take Acquisition Actions to purchase such
Subject Facility, or an interest therein, and (c) a statement that the TEPCO
International Group believes it has a reasonable probability of acquiring such
Subject Facility, or an interest therein, in such Negotiated Transaction. The
Company shall provide a written response (a "Response") to any and all Facility
Notices, which Response shall indicate whether or not the Company intends to
take Acquisition Actions with respect to the purchase of the Subject Facility,
or an interest therein (a Response stating that the Company does not have such
intention is referred to as a "No Intention Response"). Such Response shall be
given in good faith, taking into account all relevant facts and circumstances,
within sufficient time (a "Response Period") to allow the TEPCO International
Group, if a No Intention Response is given, to pursue, on a commercially
reasonable basis, the purchase of such Subject Facility, or an interest
therein, in the Negotiated Transaction. Prior to the receipt of a Response to a
Facility Notice, the TEPCO International Group shall take no Acquisition
Actions with respect to the Subject Facility.

                    (ii)     In the event the Company indicates in a Response
that it intends to take Acquisition Actions with respect to the purchase of the
Subject Facility, or an interest therein, through a Negotiated Transaction (a
"Positive Response"), the TEPCO International Group shall be precluded from
taking any Acquisition Actions with respect to the Subject Facility; provided,
however, that in the event that the Company, after

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initially giving a Positive Response with respect to the purchase of such
Subject Facility, or an interest therein, subsequently decides not to pursue
such purchase, the Company shall promptly provide a No Intention Response to
the TEPCO International Group with respect to such Subject Facility. If the
Company gives a No Intention Response, the TEPCO International Group shall have
the right to take Acquisition Actions with respect to the purchase of the
Subject Facility, or an interest therein.

                    (iii)    In the event that, during negotiations with
respect to a Negotiated Transaction, the seller of the Subject Facility
commences an Auction, the provisions of Section 3 shall apply to such Subject
Facility, and the TEPCO International Group shall immediately terminate any
Acquisition Actions with respect to such Subject Facility unless a Granting
Notice is given with respect to such Subject Facility.

         SECTION 5. Excluded Assets. Notwithstanding the foregoing, the TEPCO
International Group shall have the right to take Acquisition Actions, with
respect to (i) any interest in an existing Facility owned by the TEPCO
International Group as of the date of this Agreement, (ii) to a Greenfield
Project and (iii) any interest in a Facility in which TEPCO International and a
Person identified in a separate letter between the Company and TEPCO
International dated the date hereof, have a joint investment, whether before or
after the date of this Agreement.

         SECTION 6. Representations and Warranties. Each party represents and
warrants to the other parties that: (i) it is duly organized, validly existing
and in good standing under the laws of the jurisdiction of its formation, (ii)
it has all regulatory authorizations necessary for it to legally perform its
obligations under this Agreement and any other documentation relating to this
Agreement, (iii) the execution, delivery and performance of this Agreement and
any other documentation relating to this Agreement are within its powers, have
been duly authorized by all necessary action and do not violate any of the
terms and conditions in its governing documents, any material contracts to
which it is a party or any law, rule or regulation material to it or order or
the like applicable to it, (iv) this Agreement and each other document executed
and delivered in accordance with this Agreement constitutes its legally valid
and binding obligation enforceable against it in accordance with its terms, (v)
there are no bankruptcy proceedings pending or being contemplated by it or, to
its knowledge, threatened against it, and (vi) there is not pending or, to its
knowledge, threatened against it or any of its affiliates, any legal
proceedings that could materially adversely affect its ability to perform its
obligations under this Agreement or any other document relating to this
Agreement to which it is a party.

         SECTION 7.  Assignment. No party shall assign this Agreement or its
rights or obligations hereunder to any party without the prior written consent
of the other party.

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         SECTION 8. Amendment and Waiver. No modification, amendment or waiver
of any provision of this Agreement shall be effective against any party unless
such modification, amendment or waiver is approved in writing by such party.
The failure of any party to enforce any of the provisions of this Agreement
shall in no way be construed as a waiver of such provisions and shall not
affect the right of such party thereafter to enforce each and every provision
of this Agreement in accordance with its terms.

         SECTION 9. Severability. Whenever possible, each provision of this
Agreement shall be interpreted in such manner as to be effective and valid
under applicable law, but if any provision of this Agreement is held to be
invalid, illegal or unenforceable in any respect under any applicable law or
rule in any jurisdiction, such invalidity, illegality or unenforceability shall
not affect any other provision or any other jurisdiction, but this Agreement
shall be reformed, construed and enforced in such jurisdiction as if such
invalid, illegal or unenforceable provision had never been contained herein.

         SECTION 10. Entire Agreement. This Agreement and the other writings
referred to herein or delivered pursuant hereto which form a part hereof
contain the entire agreement and understanding among the parties hereto with
respect to the subject matter hereof and supersedes and preempts any prior
understandings, agreements or representations by or among the parties, written
or oral, which may have related to the subject matter hereof in any way.

         SECTION 11. Counterparts. This Agreement may be executed in separate
counterparts each of which, when delivered to the other party, shall be an
original and all of which taken together shall constitute one and the same
agreement.

         SECTION 12. Notices. Any notice provided for in this Agreement shall
be in writing and shall be either personally delivered or sent by facsimile or
reputable overnight courier service (charges prepaid) to the Company and TEPCO
International at the addresses set forth below, or at such address or to the
attention of such other person as the recipient party has specified by prior
written notice to the sending party. Notices will be deemed to have been given
hereunder when delivered personally or on receipt.

         The Company's address is:        Orion Power Holdings, Inc.
                                          7 East Redwood Street
                                          10th Floor
                                          Baltimore, Maryland  21202
                                          Facsimile:  (410) 234-0994
                                          Attention:  General Counsel

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                                          with a copy to:

                                          Fried, Frank, Harris,
                                          Shriver & Jacobson
                                          One New York Plaza
                                          New York, New York  10004
                                          Facsimile: (212) 859-8000
                                          Attention: Paul M. Reinstein, Esq.

         TEPCO International Group's
         address is:                      Tokyo Electric Power Company
                                          International B.V.
                                          Officia 1, De Boelelaan 7, 1083HJ
                                          Amsterdam, The Netherlands
                                          Facsimile:  31-20-642-7675
                                          Attention:  BTM Trust (Holland) B.V.

                                          with a copy to:

                                          The Tokyo Electric Power Company
                                          1-3 Uchisaiwai-cho 1-chome Chiyoda-ku
                                          Tokyo 100-0011 Japan
                                          Facsimile:  81-3-3596-8438
                                          Attention:  Business Development Group
                                          International Affairs Department

                                          with a copy to:

                                          Morgan, Lewis & Bockius LLP
                                          300 S. Grand Avenue, 22nd Floor
                                          Los Angeles, California 90071
                                          Facsimile:  (213) 612-2554
                                          Attention:  Richard A. Shortz, Esq

         SECTION 13. Governing Law; Submission to Jurisdiction; Waiver of Jury
Trial This Agreement shall be governed by and construed in accordance with the
laws of the State of New York without giving effect to the principles of
conflicts of law. Each of the parties hereto hereby irrevocably and
unconditionally consents to submit to the exclusive jurisdiction of the courts
of the State of New York and of the United States of America, in each case
located in the County of New York, for any action, proceeding or investigation
in any court or before any governmental authority ("Litigation") arising out of
or relating to this Agreement and the transactions contemplated hereby (and
agrees not to commence any Litigation relating thereto except in such courts),
and further agrees that service of any process, summons, notice or document by
U.S. registered mail to its respective address set forth in this Agreement
shall be effective service of process for any Litigation brought against it in
any such court. Each of the parties hereto hereby irrevocably and
unconditionally

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waives any objection to the laying of venue of any Litigation arising out of
this Agreement or the transactions contemplated hereby in the courts of the
State of New York or the United States of America, in each case located in the
County of New York, and hereby further irrevocably and unconditionally waives
and agrees not to plead or claim in any such court that any such Litigation
brought in any such court has been brought in an inconvenient forum. Each of
the parties irrevocably and unconditionally waives, to the fullest extent
permitted by applicable law, any and all rights to trial by jury in connection
with any Litigation arising out of or relating to this Agreement or the
transactions contemplated hereby.

         SECTION 14.  Descriptive Headings.  The descriptive headings of this
Agreement are inserted for convenience only and do not constitute a part of
this Agreement.

         SECTION 15. Construction. Where specific language is used to clarify
by example a general statement contained herein, such specific language shall
not be deemed to modify, limit or restrict in any manner the construction of
the general statement to which it relates. The language used in this Agreement
shall be deemed to be the language chosen by the parties hereto to express
their mutual intent, and no rule of strict construction shall be applied
against any party.

         SECTION 16. Remedies. Each party hereto shall be entitled to enforce
its rights under this Agreement specifically to recover damages by reason of
any breach of any provision of this Agreement and to exercise all other rights
existing in its favor. The parties hereto agree and acknowledge that money
damages may not be an adequate remedy for any breach of the provisions of this
Agreement and that each party may in its sole discretion apply to any court of
law or equity of competent jurisdiction for specific performance and/or
injunctive relief (without posting a bond or other security) in order to
enforce or prevent any violation of the provisions of this Agreement. In no
case shall any party be liable to the other for a breach of this Agreement for
consequential, indirect, punitive or special damages.

         SECTION 17. Confidentiality. The parties hereto shall keep the
existence and the terms of this Agreement strictly confidential unless (i) the
disclosing party has received the advice of independent counsel that such
disclosure is required by any law (including, without limitation, any judicial
order) or other requirement of any governmental entity to which the disclosing
party is subject (provided that prior to such disclosure, the disclosing party
promptly advises and consults with the non-disclosing parties concerning the
information it proposes to disclose), (ii) the disclosing party discloses such
information to a potential purchaser of Company equity held by the disclosing
party (provided that prior to such disclosure, the potential purchaser executes
a confidentiality agreement imposing confidentiality obligations on such
potential purchaser with respect to any non-competition agreement substantially
identical to the confidentiality obligations imposed by this Section 17) or
(iii) such

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information becomes publicly available (other than as a result of any act or
omission by such disclosing party).

                           [INTENTIONALLY LEFT BLANK]

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IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of the
date first above written.

                            ORION POWER HOLDINGS, INC.

                            By:
                                  -------------------------------------
                                  Name:    Jack Fusco
                                  Title:   Chief Operating Officer

                            TOKYO ELECTRIC POWER COMPANY
                            INTERNATIONAL, B.V.

                            By:
                                  -------------------------------------
                                  Name:
                                  Title:

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                TOKYO ELECTRIC POWER COMPANY INTERNATIONAL B.V.
                       Officia 1, De Boelelaan 7, 1083HJ
                           Amsterdam, The Netherlands

November ___, 1999

Orion Power Holdings, Inc.
7 East Redwood Street, 10th Floor
Baltimore, Maryland 21202

RE:      NON-COMPETITION AGREEMENT, BY AND BETWEEN TOKYO ELECTRIC POWER COMPANY
         INTERNATIONAL B.V. AND ORION POWER HOLDINGS, INC., DATED AS OF EVEN
         DATE HEREWITH

Ladies and Gentlemen:

Reference is hereby made to that certain Non-Competition Agreement, by and
between Tokyo Electric Power Company International B.V. ("TEPCO International")
and Orion Power Holdings, Inc. ("Orion"), dated as of even date herewith (the
"Non-Competition Agreement"). Capitalized terms used herein but not otherwise
defined shall have the meaning ascribed to them in the Non-Competition
Agreement.

For purposes of Section 5(iii) of the Non-Competition Agreement, TEPCO
International and Orion hereby agree that the Persons to be identified in
accordance with the terms thereof is hereby identified as Tenaska, Inc. and its
affiliates.

Sincerely yours,

TOKYO ELECTRIC POWER COMPANY
INTERNATIONAL B.V.

By:
   -----------------------------------------
Name:
     ---------------------------------------
Its:
    ----------------------------------------

AGREED AND ACKNOWLEDGED:

ORION POWER HOLDINGS, INC.

By:
   -----------------------------------------
Name:
     ---------------------------------------
Its:
    ----------------------------------------<PAGE>   1
                                                                   Exhibit 10.25

                                                                  EXECUTION COPY

                           THIRD AMENDED AND RESTATED
                             STOCKHOLDERS' AGREEMENT

                                  by and among

                           ORION POWER HOLDINGS, INC.,

             GS CAPITAL PARTNERS II, L.P. (AND CERTAIN AFFILIATES),

            CONSTELLATION ENTERPRISES, INC. (AND CERTAIN AFFILIATES),

                  CERTAIN AFFILIATES OF MITSUBISHI CORPORATION

                                       and

                 TOKYO ELECTRIC POWER COMPANY INTERNATIONAL B.V.

                           Dated as of April 26, 2000

<PAGE>   2

               THIRD AMENDED AND RESTATED STOCKHOLDERS' AGREEMENT

        THIS THIRD AMENDED AND RESTATED STOCKHOLDERS' AGREEMENT, dated as of
April 26, 2000 (this "Agreement"), is entered into by and among Orion Power
Holdings, Inc. (the "Company"), GS Capital Partners II, L.P. ("GSCP II,"
together with any Affiliate (as defined below) (including without limitation,
the Other GSCP Entities, as defined below) to which it assigns any rights and
obligations under the Agreement, "GSCP"), GS Capital Partners III, L.P. ("GSCP
III"), GS Capital Partners II Offshore, L.P. ("GSCP Offshore"), GS Capital
Partners III Offshore, L.P. ("GSCP III Offshore"), Goldman, Sachs & Co.
Verwaltungs GmbH, as nominee for GS Capital Partners II Germany C.L.P. ("GS
Germany") and as nominee for GS Capital Partners III Germany C.L.P. ("GS III
Germany"), Stone Street Fund 1998, L.P. ("Stone"), Bridge Street Fund 1998, L.P.
("Bridge,") Stone Street Fund 2000, L.P. ("Stone 2000") and Bridge Street Fund
2000, L.P. ("Bridge 2000," and collectively with GSCP III, GSCP Offshore, GSCP
III Offshore, GS Germany, GS III Germany, Stone, Bridge and Stone 2000, the
"Other GS Entities"), Constellation Enterprises, Inc. ("Constellation"),
Constellation Operating Services, Inc. ("COSI"), Diamond Generating Corporation
("DGC"), Diamond Cayman, Inc. ("DCI"), Mitsubishi International Corporation
("MIC," and collectively with DGC and DCI, "Mitsubishi"), and Tokyo Electric
Power Company International B.V. ("TEPCO International").

                               W I T N E S S E T H

        WHEREAS, GSCP and Constellation Power Source, Inc. ("CPS") have caused
the formation of the Company for the purpose of investing in and managing the
operations of a portfolio of electric generating assets in the United States and
Canada (the "Portfolio Assets");

        WHEREAS, GSCP and CPS entered into a stockholders' agreement (the
"Stockholders' Agreement"), dated as of March 10, 1998, by and among the
Company, GSCP and Constellation and the other parties named therein, as amended
from time to time;

        WHEREAS, on November 5, 1999, the Company, GSCP, CPS, Mitsubishi and
TEPCO International amended and restated the Stockholders' Agreement in its
entirety ( the "Second Amended and Restated Stockholders' Agreement")

        WHEREAS, on December 2, 1999, CPS assigned its rights and obligations
under the Second Amended and Restated Stockholders' Agreement to Constellation.

        WHEREAS, on April 26, 2000, the Company and COSI entered into a Stock
Purchase Agreement (the "COSI Purchase Agreement"), pursuant to which the
Company agreed to issue to COSI, 12,193.548 shares of Common Stock in
consideration for the acquisition of various assets.

        WHEREAS, the parties hereto and the Company anticipate that the Company
will conduct an IPO (as defined herein).

        WHEREAS, the parties hereto desire to amend and restate the Second
Amended and Restated Stockholders' Agreement in its entirety to set forth the
relative rights and obligations of the parties hereto in connection with the
management and operation of the Company prior to the anticipated IPO.

<PAGE>   3

        NOW, THEREFORE, in consideration of the premises and of the mutual
covenants and obligations hereinafter set forth, the parties hereto hereby agree
as follows:

Section 1.        Definitions.

        As used herein, the following terms shall have the following meanings:

        "Affiliate" means, with respect to any Person, any other Person directly
or indirectly controlling or controlled by or under direct or indirect common
control with such specified Person; provided, however, that, for purposes
hereof, neither the Company nor any Person controlled by the Company shall be
deemed to be an Affiliate of any Stockholder.

        "Beneficially Owned" has the meaning set forth in Rule 13d-3 under the
Exchange Act.

        "Board" means the Board of Directors of the Company.

        "Book Value" of a share of Common Stock shall mean the stockholders'
equity as shown on the books of the Company related to the Common Stock, divided
by the number of shares of Common Stock outstanding at the time such calculation
is made.

        "Business Day" means any day excluding Saturday, Sunday and any day on
which banks in the State of New York are authorized or required by law or other
governmental action to close.

        "Capital Call" means notice by the Company that a person is required to
purchase Stock pursuant to a Capital Commitment or pursuant to any other Sale of
capital stock of the Company prior to an IPO.

        "Capital Commitments" shall mean the respective commitments of GSCP,
Constellation, Mitsubishi and TEPCO International to purchase Common Stock
pursuant to Section 3(a) of this Agreement.

        "Common Stock" means the common stock, par value $.01 per share, of the
Company.

        "Common Stock Equivalents" means securities convertible into, or
exchangeable or exercisable for, shares of Common Stock.

        "COSI Shares" means the 12,193.548 shares of Common Stock acquired by
COSI pursuant to the COSI Purchase Agreement, including any shares of Common
Stock acquired upon any stock split, stock dividend or recapitalization with
respect to such shares.

        "Designated Director" means a GSCP Director, Constellation Director or
New Investors' Director, as the context requires.

        "Designating Party" means (i) with respect to any GSCP Director, GSCP,
GSCP II or GSCP III, as the case may be, (ii) with respect to any Constellation
Director, Constellation and (iii) with respect to any New Investors' Director,
Mitsubishi and TEPCO International, jointly, which designation shall be
communicated to the Company by Mitsubishi.

<PAGE>   4

        "Discretionary Pool" means a pool of Warrants (as defined in Section 5)
in the amount set forth in Section 5 which may be (but shall not be required to
be) allocated to the Company's management in such amounts, if any, and upon such
terms, as the Board, in its sole discretion, deems appropriate.

        "ERISA" means the Employee Retirement Income Security Act of 1974 (and
any sections of the Internal Revenue Code of 1986 amended by it) and all
regulations promulgated thereunder, as amended.

        "HSR" means the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as
amended.

        "IPO" means an underwritten offering or series of underwritten offerings
pursuant to which the Common Stock becomes registered under Section 12 of the
Securities Exchange Act of 1934, as amended (the "Exchange Act") (a) in which
either (i) the Common Stock issued constitutes at least 20% of the Common Stock
or (ii) the gross proceeds to the Company and any Selling Stockholders, in the
aggregate, is at least $75 million before deducting underwriting discounts,
commissions and offering expenses and (b) which results in the Common Stock
being held by at least 500 holders of record within the meaning of Rule 12g5-1
under the Exchange Act.

        "Other Stockholders" means, with respect to any Selling Stockholder, the
Stockholders other than the Selling Stockholder or its Affiliates.

        "Person" means any individual, corporation, limited liability company,
limited or general partnership, joint venture, association, joint-stock company,
trust, unincorporated organization or government or any agency or political
subdivisions thereof.

        "Portfolio Asset" means any electric generating assets located in the
United States or Canada.

        "Preferred Stock" means the preferred stock, par value $.01 per share,
of the Company.

        "Public Sale" means a Sale pursuant to a bona fide underwritten public
offering pursuant to an effective registration statement filed under the
Securities Act of 1933, as amended (the "Securities Act") or pursuant to Rule
144 under the Securities Act (other than in a privately negotiated Sale).

        "Sell" means (i) for purposes of this Agreement other than Section 3 and
Section 4, to sell, or in any other way directly or indirectly transfer, assign,
distribute, pledge, encumber or otherwise dispose of, either voluntarily or
involuntarily, and (ii) for purposes of Section 3 and Section 4 of this
Agreement only, to issue or in any other way directly or indirectly sell or
exchange, or agree to issue, sell or exchange; and the terms "Sale," "Selling"
and "Sold" shall have meanings correlative to the foregoing.

        "Stock" means (i) any shares of Common Stock and/or (ii) any Common
Stock Equivalents, in each case whether owned as of the date of this Agreement
or acquired hereafter.

<PAGE>   5

        "Stockholders" means any holder of Stock or Voting Shares who agrees to
be bound by the terms of this Agreement.

        "Strategic Alliance Agreement" means the Strategic Alliance Agreement,
dated as of March 10, 1998, between the Company and Constellation.

"Total Capital Commitments" means the sum of all Capital Commitments.

        "Voting Shares" means any securities of the Company, the holders of
which are generally entitled to vote for members of the Board (including,
without limitation, all outstanding shares of Common Stock).

        Section 2. Calculations.

        (a) Except as otherwise set forth in Section 5, for all purposes of this
Agreement, the proposed Sale or the Sale of a Common Stock Equivalent shall be
treated as the proposed Sale or the Sale of the shares of Common Stock into
which such Common Stock Equivalent can be converted, exchanged or exercised.

        (b) Except as set forth herein, the amount of outstanding Common Stock
as of any date and the amount of Common Stock owned by a Person hereunder (and
the percentage of the outstanding Common Stock owned by a Person) shall be
calculated on a Fully Diluted Basis. For the purposes of this Agreement, "Fully
Diluted Basis" shall mean (i) giving effect to full funding of the Capital
Commitments, (ii) treating all Common Stock Equivalents of the Company then
outstanding as having been converted, exchanged or exercised (excluding any
Common Stock Equivalents having an exercise or conversion price in excess of the
price per share to be paid by the purchaser in the relevant transaction) and
(iii) excluding any Common Stock and Common Stock Equivalents owned by Persons
other than the Stockholders .

Section 3.  Commitments.

(a)     Capital Commitments.

(i)     Subject to the terms of this Agreement, (A) GSCP has committed to
purchase an aggregate of 300,000 shares of Common Stock at $1,000 per share, for
an aggregate commitment of $300 million, (B) Constellation has committed to
purchase an aggregate of 175,000 shares of Common Stock at $1,000 per share, for
an aggregate commitment of $175 million, (C) Mitsubishi has committed to
purchase an aggregate of 77,419.355 shares of Common Stock at $1,550 per share,
for an aggregate commitment of $120 million, which commitment shall be allocated
as follows:

         DGC               36,774.194 shares at $1,550.00 per share

         DCI               36,774.194 shares at $1,550.00 per share

         MIC               3,870.967 shares at $1,550.00 per share,

<PAGE>   6

and (D) TEPCO International has committed to purchase an aggregate of 51,612.903
shares of Common Stock at $1,550 per share, for an aggregate commitment of $80
million (the Capital Commitments pursuant to this Section 3(a) being referred to
as the "Capital Commitments "). The number of shares to be purchased and the
purchase price per share with respect to each Stockholder's Capital Commitment
shall be appropriately adjusted, if necessary, to reflect any stock dividends,
stock-splits or reverse stock-splits occurring after the date hereof.

        (ii)  On or prior to the date hereof, each Stockholder has purchased
shares of Common Stock in complete fulfillment of their respective Capital
Commitments.

Section 4.    Limited Preemptive Rights.

        Prior to an IPO, the Company shall not issue any Common Stock, Common
Stock Equivalents or other Company equity securities or convertible equity
except in compliance with the provisions of this Section 4. This Section 4 shall
not be applicable to (i) the issuance of Company equity securities to a seller
of Portfolio Assets in consideration for the sale of such Portfolio Assets, (ii)
the issuance of Company equity securities in accordance with Sections 3 and 5
above and (iii) the issuance of Common Stock in connection with the exercise of
Common Stock Equivalents (including, without limitation, the Warrants);
provided, however, that in the case of an issuance of the type referred to in
clause (i) hereof, Constellation shall have preemptive rights to purchase the
portion of the equity in such issuance necessary to prevent its Ownership
Percentage (as defined below) from falling below 20% as a result of such
issuance, which rights shall be exercisable in the same manner as the limited
preemptive rights of all the Stockholders set forth in Sections 4(a) through
4(f) hereof.

        (a)   In the event that, prior to an IPO, the Company desires to issue
additional Common Stock, Common Stock Equivalents or any units containing Common
Stock or Common Stock Equivalents, or any other equity securities or convertible
securities, the Company shall (i) notify (a "Section 4 Offer Notice") each of
Mitsubishi, TEPCO International, GSCP and Constellation (the "Section 4
Stockholders") describing the type of securities (i.e., Common Stock, Common
Stock Equivalents or any units containing Common Stock or Common Stock
Equivalents, or any other equity securities or convertible securities) offered
for issuance (the "Section 4 Securities"), the purchase price therefor and a
summary of the other material terms of the proposed issuance (the "Proposed
Price and Terms"), and (ii) offer (the "Section 4 Offer") each of the Section 4
Stockholders the option to acquire, at the Proposed Price and Terms, up to a
proportionate amount of shares of the Section 4 Securities (as applicable, the
"Proportionate Securities"), such that:

        (A)   in the case of a sale of Common Stock, Common Stock Equivalents or
any units containing Common Stock or Common Stock Equivalents, the percentage of
the outstanding Common Stock ownership interest of each of the Section 4
Stockholders immediately prior to issuance (the "Ownership Percentage") shall
not be diminished as a result of issuance of the Section 4 Securities. The
Ownership Percentage of each Section 4 Stockholder as of the date hereof is set
forth on Annex A attached hereto. Each Section 4 Stockholder's right to maintain
its Ownership Percentage is referred to hereinafter as the "Ownership
Maintenance Right"; and

<PAGE>   7

        (B)   in the case of a sale of equity securities or convertible
securities other than Common Stock, Common Stock Equivalents or any units
containing Common Stock or Common Stock Equivalents ("Other Equity"), the
percentage of such Other Equity held by each of the Section 4 Stockholders
shall, for purposes of this Section 4, be deemed to equal such Section 4
Stockholder's Ownership Percentage. Each Section 4 Stockholder's right to
maintain a percentage of Other Equity equal to its Ownership Percentage is
referred to hereinafter as the "Other Equity Maintenance Right."

        (b)   The Section 4 Offer shall remain open and irrevocable for the
periods set forth below (and, to the extent the Section 4 Offer is accepted
during such periods, such offer and acceptance shall be binding on such Section
4 Stockholder and the Company). Each Section 4 Stockholder shall have the right,
for a period of 30 days after delivery of the Section 4 Offer Notice (the
"Section 4 Acceptance Period"), to exercise its right to purchase all or any
part of its Proportionate Securities at the Proposed Price and Terms. Such
exercise shall be made by a Section 4 Stockholder by delivering a written notice
to the Company within the Section 4 Acceptance Period specifying the maximum
portion of the Section 4 Securities such Section 4 Stockholder will purchase.

        (c)   In the event that any of the Section 4 Stockholders fail to
exercise their respective rights to purchase all the Section 4 Securities within
the Section 4 Acceptance Period, the Company shall have 120 days from the
expiration of the Section 4 Acceptance Period to enter into an agreement
(pursuant to which the sale of such securities shall be closed, if at all,
within 45 days from the date of such agreement, or such longer period as may be
necessary to obtain any required regulatory approval, but in no case to exceed 6
months) to sell to a third party purchaser (the "Section 4 Purchaser") at the
Proposed Price and Terms (or at a price and on terms not more favorable to the
Section 4 Purchaser than the Proposed Price and Terms) any Section 4 Securities
not elected to be purchased by any of the Section 4 Stockholders (the "Excess
Section 4 Securities"). The foregoing periods are referred to hereinafter in the
aggregate as the "Section 4 Issuance Period." The Company shall provide written
notice (the "Notice of Section 4 Sale") to all of the Section 4 Stockholders at
least 10 days prior to the closing of the sale of the Excess Section 4
Securities; provided, however, in the case of a Sale in which the Company is to
receive non-cash consideration, the Company shall provide the Notice of Section
4 Sale at least 45 days prior to the closing, including information regarding
the form of consideration payable by the Section 4 Purchaser.

        (d)   In the event that the consideration payable to the Company by a
Section 4 Purchaser for Excess Section 4 Securities is in a form other than cash
(excluding marketable securities listed on a national securities exchange or the
Nasdaq National Market, the value of which shall be determined by calculation of
such securities' average price over the 10 trading days prior to delivery of the
Notice of Section 4 Sale), any Section 4 Stockholder shall have the right to
require the Company to commission, at the Company's expense, an appraisal of the
value of the non-cash consideration acquired by the Company from the Section 4
Purchaser (the "Appraisal"), by delivery of written notice of the same within 10
days after the receipt of a Notice of Section 4 Sale. The Company shall use its
commercially reasonable efforts to complete the Appraisal prior to the
expiration of the Section 4 Issuance Period; provided, however, that if the
Appraisal is not completed during the original term of the Section 4 Issuance

<PAGE>   8

Period, such period shall be extended to the date which is 10 days after such
Appraisal is completed. If the Appraisal (or calculation of the value of
marketable securities set forth above, if applicable) indicates that the value
of the non-cash consideration payable by the Section 4 Purchaser is less than
the aggregate value of the per share price, as set forth in the Proposed Price
and Terms, for all of the Excess Section 4 Securities, the Company shall not
sell the Excess Section 4 Securities to such Section 4 Purchaser unless such
Section 4 Purchaser pays the difference to the Company in the form of cash.

        (e)   In the event that the Company has not closed the transactions for
the sale of all Excess Section 4 Securities, if any, by the termination of the
Section 4 Issuance Period, the Company shall not thereafter issue or sell the
Excess Section 4 Securities without first offering such securities to the
Section 4 Stockholders in compliance with this Section 4.

        (f)   All Sales of Section 4 Securities to the Section 4 Stockholders
subject to any Section 4 Offer Notice shall be consummated contemporaneously at
the offices of the Company on the later of (i) the closing of the Sale of the
Excess Section 4 Securities which are Sold to a Section 4 Purchaser or (ii) the
fifth Business Day following the expiration or termination of all waiting
periods under HSR applicable to such issuance, or at such other time and/or
place as the Company and the Section 4 Stockholders may agree. The delivery of
certificates or other instruments evidencing such Section 4 Securities shall be
made by the Company on such date against payment of the purchase price for such
Section 4 Securities.

Section  5.   Warrants; Reservation of Common Stock. Subject to Section 5(b)
         herein, (a) At the time of a Capital Call, the Company shall (i) issue
         warrants for shares of Common Stock to GSCP or Constellation (in
         accordance with the allocation set forth in this paragraph (a)) and
         (ii) allocate warrants (or options) for shares of Common Stock to the
         Discretionary Pool (the warrants (or options) in clauses (i) and (ii)
         above referred to as the "Warrants") in an amount, for Warrants
         purchased pursuant to clauses (i) and (ii) above, equal to an aggregate
         of 15% of the number of shares of Common Stock issued pursuant to such
         Capital Call plus the number of shares of Common Stock issuable upon
         conversion or exercise of Common Stock Equivalents issued pursuant to
         such Capital Call (but not including any Common Stock obtainable upon
         conversion, exchange or exercise of Preferred Stock). With respect to
         each Capital Call, 1/3 of the Warrants shall be allocated to the
         Discretionary Pool and 2/3 shall be allocated to GSCP; provided,
         however, that with respect to the last $60 million of Capital
         Contributions made by Constellation, 1/3 of the Warrants shall be
         allocated to the Discretionary Pool and 2/3 of the Warrants shall be
         allocated to Constellation. The Warrants shall have exercise prices, in
         the case of Warrants issued to GSCP and Constellation, equal to the
         applicable subscription price paid by each Stockholder for Common Stock
         to which the Warrants relate (i.e., in the case of warrants
         attributable to Common Stock issued to Mitsubishi and TEPCO
         International, $1550 per share, and in the case of warrants
         attributable to Common Stock issued to GSCP and Constellation, $1000
         per share, as adjusted for stock-splits, reverse stock-splits and stock
         dividends) and, in the case of Warrants allocated to the Discretionary
         Pool, as the Board in its sole discretion shall determine. In the event
         that the Company issues any Warrants to GSCP and/or Constellation
         pursuant to this Section 5(a) in excess of the aggregate amounts set
         forth in Section 5(b), such Warrants

<PAGE>   9

         shall be of no force or effect, and the Company and GSCP or
         Constellation, as applicable, shall promptly terminate such excess
         Warrants.

        (b)   Notwithstanding anything herein to the contrary, (i) in no event
shall the Company issue to GSCP warrants to purchase more than 64,004 shares of
Common Stock in the aggregate and (ii) in no event shall the Company issue to
Constellation warrants to purchase more than 7,059 shares of Common Stock in the
aggregate. After the maximum number of Warrants under this Agreement are issued
to GSCP and Constellation as set forth in the preceding sentence (such number
being referred to herein as the "Stockholder Limit"), at the time of a Capital
Call (including any portion of a Capital Call with respect to which Warrants
were not issued before the Stockholder Limit was reached), the Board, in its
discretion, may allocate Warrants to the Discretionary Pool in an amount equal
to an aggregate of 5% of the number of shares of Common Stock issued pursuant to
such Capital Call (excluding any shares with respect to which Warrants were
issued before the Stockholder Limit was reached) plus the number of shares of
Common Stock issuable upon conversion or exercise of Common Stock Equivalents
issued pursuant to such Capital Call (excluding any shares with respect to which
Warrants were issued before the Stockholder Limit was reached).

        (c)   The Company shall at all times reserve and keep available out of
its authorized but unissued shares of Common Stock a sufficient number of shares
of Common Stock to permit exercise of the Warrants. All shares of Common Stock
which are so issuable shall, when issued, in accordance with this Section 5 and
upon receipt by the Company of the exercise price therefor, be duly and validly
issued, fully paid and nonassessable and free from all taxes, liens and charges.
The Company shall take all such actions as may be necessary to assure that all
such shares of Common Stock may be so issued without violation of any applicable
law or governmental regulation or any requirements of any domestic securities
exchange upon which such shares may be listed (except for official notice of
issuance which shall be immediately transmitted by the Company upon issuance).

Section  6.   Corporate Governance.

         6.1. Board of Directors.

        (a)   As of the date hereof, the Board shall be comprised of eight
members. Prior to an IPO and subject to Sections 8(c) and (d): (i) GSCP II shall
have the right to designate three persons to serve as members of the Board and
GSCP III shall have the right to designate one person to serve as a member of
the Board (such members being collectively referred to herein as "GSCP
Directors"), (ii) Constellation shall have the right to designate one member of
the Board (such member being referred to herein as the "Constellation
Director"), (iii) Mitsubishi and TEPCO International shall jointly have the
right to designate one member of the Board (such member being referred to herein
as the "New Investors' Director"), which designation shall be communicated to
the Company by Mitsubishi, (iv) the Chief Executive Officer of the Company shall
be appointed by the Board and shall serve as a member of the Board, and (v) the
Board may appoint a person to serve as a member of the Board and to act as
Chairman of the Board. In addition, Mitsubishi and TEPCO International shall
jointly have the right to appoint one

<PAGE>   10

designated, non-voting observer to attend all meetings of the Board (the "New
Investors' Observer"), which designation shall be communicated to the Company by
Mitsubishi.

        (b)   Prior to an IPO, at any regular or special meeting of shareholders
called for the purpose of electing members to serve on the Board, or, to the
extent permitted by the Certificate of Incorporation, in any written consent
electing members to serve on the Board executed in lieu of such a meeting, each
of the parties hereto agrees to vote all Voting Shares held by it, and to take
all other necessary action, to cause the Board to be comprised of the GSCP
Directors, the Constellation Director, the New Investors' Director and the Chief
Executive Officer of the Corporation.

        6.2.     Vacancies; Removal.

        (a)   Subject to Section 6.2(b), each Designated Director shall hold his
office until his death or until his successor shall have been duly elected and
qualified. If any Designated Director shall cease to serve as a director of the
Company for any reason, the vacancy resulting thereby shall be filled by another
Person selected by his Designating Party.

        (b)   No Designated Director shall be removed from office without the
written consent of his Designating Party. With respect to any Designated
Director, at the request of his Designating Party, all Stockholders shall take
such action requested by such Designating Party to remove such Designated
Director from office.

        6.3.  Telephonic Board Meetings.

        The Company shall take or cause to be taken all necessary actions,
including, without limitation, causing its By-Laws to make due provision, to
allow any member of the Board to telephonically attend any meeting of the Board.

        6.4.  Directors' Indemnification.

        (a)   The Certificate of Incorporation, By-Laws and other organizational
documents of the Company shall at all times, to the fullest extent permitted by
law, provide for indemnification of, advancement of expenses to, and limitation
of the personal liability of, the members of the Board and such other persons,
if any, who, pursuant to a provision of such Certificate of Incorporation,
By-laws or other organizational documents, exercise or perform any of the powers
or duties otherwise conferred or imposed upon members of the Board. Such
provisions may not be amended, repealed or otherwise modified in any manner
adverse to any member of the Board until at least six years following the date
that none of GSCP II, GSCP III, Constellation or Mitsubishi and TEPCO
International, jointly, is entitled to designate any Designated Director.

        (b)   Each member of the Board is intended to be a third-party
beneficiary of the obligations of the Company pursuant to this Section 6.4, and
the obligations of the Company pursuant to this Section 6.4 shall be enforceable
by each member of the Board.

        6.5.  Cooperation.
<PAGE>   11

        Each Stockholder shall vote all of its or his Voting Shares and shall
take all other necessary or desirable actions within its or his control
(including, without limitation, attending all meetings in person or by proxy for
purposes of obtaining a quorum and/or executing all written consents in lieu of
meetings, as applicable), and the Company shall take all necessary and desirable
actions within its control (including, without limitation, providing therefor in
its organizational documents and/or calling special Board and Stockholder
meetings), to effectuate the provisions of this Section 6.

        6.6.  Irrevocable Proxy.

        (a)   In order to secure each Stockholder's obligation to vote his, her
or its Voting Shares in accordance with the provisions of Section 6 of this
Agreement, each Stockholder hereby appoints GSCP as his, her or its true and
lawful proxy and attorney-in-fact, with full power of substitution, to vote all
of his, her or its Voting Shares of the Company as is necessary to enforce the
rights of GSCP under Section 6 of this Agreement until such rights are
terminated in accordance with the terms of this Agreement. GSCP may exercise the
irrevocable proxy granted to it hereunder at any time any Stockholder fails to
comply with any provision of Section 6 of this Agreement granting GSCP rights
thereunder. The proxies and powers granted by each Stockholder pursuant to this
Section 6.6(a) are coupled with an interest and are given to secure the
performance of the Stockholder's obligations to GSCP under Section 6 of this
Agreement. Such proxies and powers will be effective until an IPO, at which time
such proxies and powers shall terminate. Such proxies and powers shall survive
the death, incompetency and disability of each Stockholder.

        (b)   In order to secure each Stockholder's obligation to vote his, her
or its Voting Shares in accordance with the provisions of Section 6 of this
Agreement, each Stockholder hereby appoints Constellation as his, her or its
true and lawful proxy and attorney-in-fact, with full power of substitution, to
vote all of his, her or its Voting Shares of the Company as is necessary to
enforce the rights of Constellation under Section 6 of this Agreement until such
rights are terminated in accordance with the terms of this Agreement.
Constellation may exercise the irrevocable proxy granted to it hereunder at any
time any Stockholder fails to comply with any provision of Section 6 of this
Agreement granting Constellation rights thereunder. The proxies and powers
granted by each Stockholder pursuant to this Section 6.6(b) are coupled with an
interest and are given to secure the performance of the Stockholder's
obligations to Constellation under Section 6 of this Agreement. Such proxies and
powers will be effective until an IPO, at which time such proxies and powers
shall terminate. Such proxies and powers shall survive the death, incompetency
and disability of each Stockholder.

        (c)   In order to secure each Stockholder's obligation to vote his, her
or its Voting Shares in accordance with the provisions of Section 6 of this
Agreement, each Stockholder hereby appoints Mitsubishi as his, her or its true
and lawful proxy and attorney-in-fact, with full power of substitution, to vote
all of his, her or its Voting Shares of the Company as is necessary to enforce
the rights of Mitsubishi and TEPCO International under Section 6 of this
Agreement until such rights are terminated in accordance with the terms of this
Agreement. Mitsubishi may exercise the irrevocable proxy granted to it hereunder
at any time any Stockholder fails to comply with any provision of Section 6 of
this Agreement granting Mitsubishi or TEPCO

<PAGE>   12

International rights thereunder. The proxies and powers granted by each
Stockholder pursuant to this Section 6.6(c) are coupled with an interest and are
given to secure the performance of the Stockholder's obligations to Mitsubishi
and TEPCO International under Section 6 of this Agreement. Such proxies and
powers will be effective until an IPO, at which time such proxies and powers
shall terminate. Such proxies and powers shall survive the death, incompetency
and disability of each Stockholder.

        6.7.  Management Rights.

        The Company acknowledges that the provisions of Section 6 of this
Agreement are intended to provide GSCP and Constellation, Mitsubishi and TEPCO
International with "contractual management rights" within the meaning of Section
2510.3-101 of the U.S. Department of Labor Code of Regulations.

Section 7.  Restrictions on Sales of Stock by Stockholders.

        (a)   Subject to Section 7(b) and Section 7(c), no Stockholder shall
Sell any Stock , whether owned on the date hereof or acquired hereafter, without
first, if applicable, complying with the provisions of Section 8 hereof.

        (b)   Anything contained in this Agreement to the contrary
notwithstanding, any transferee of Stock who is not a Stockholder shall upon
consummation of, and as a condition to, such Sale execute and deliver to the
Company (which the Company shall then deliver to all other Stockholders) an
agreement pursuant to which it agrees to be bound by the terms of this Agreement
and such transferee shall thereafter be deemed to be a Stockholder for all
purposes of this Agreement.

        (c)   Any Sale or attempted Sale of Stock in violation of any provision
of this Agreement shall be void, and the Company shall not record such Sale on
its books or treat any purported transferee of such Stock as the owner of such
Stock for any purpose.

Section 8.    Stockholder Sale of Stock/ Right of First Offer.

(a)           Subject to Section 8(a)(viii) and Section 11 hereof, no
        Stockholder may Sell any Stock to any Person except in accordance with
        the following procedures:

                                (i) The Stockholder wishing to Sell Stock
              (together with its Affiliates, the "Selling Stockholder") shall
              first deliver to the Company and the other Stockholders a
              written notice (a "Section 8 Offer Notice"), which shall (i)
              state the Selling Stockholder's intention to Sell Stock, the
              amount and type of Stock intended to be Sold (the "Subject
              Stock"), the proposed purchase price therefor and a summary of
              the other material terms of the proposed Sale (without any
              requirement to identify the proposed transferee) and (ii) offer
              the Company the option to acquire all or a portion of such
              Subject Stock upon the terms and subject to the conditions of
              the proposed Sale as set forth in the Section 8 Offer Notice
              (the "Section 8 Offer"); provided that such Section 8 Offer may
              provide tha t it must be accepted by the Company and the other
              Stockholders

<PAGE>   13

              other than such Selling Stockholder (the "Other Stockholders")
              on an all or nothing basis (an "All or Nothing Sale"). The
              Section 8 Offer shall remain open and irrevocable for the
              periods set forth below (and, to the extent the Section 8 Offer
              is accepted during such periods, until the consummation of the
              Sale contemplated by the Section 8 Offer). Subject to Section
              8(a)(vii) hereof, the Company shall have the right and option,
              for a period of 20 days after delivery of the Section 8 Offer
              Notice (the "Section 8(a)(i) Acceptance Period"), to accept all
              or any part of the Subject Stock at the purchase price, in cash,
              and on the terms stated in the Section 8 Offer Notice; provided,
              however, that, if the Section 8 Offer contemplated an All or
              Nothing Sale, the Company may accept, during the Section 8(a)(i)
              Acceptance Period, at the purchase price and on the terms stated
              in the Section 8 Offer Notice, either (x) all, but not less than
              all of the Subject Stock or (y) less than all of the Subject
              Stock, provided that such offer and acceptance shall be
              conditioned upon the Other Stockholders purchasing pursuant to
              Section 8(a)(ii) any Subject Stock not purchased by the Company.
              If a Section 8 Offer is accepted, the Company shall be
              irrevocably obligated to consummate the purchase as set forth in
              Section 8(a)(iv) below. Such acceptance shall be made by
              delivering a written notice to the Selling Stockholder and each
              of the Other Stockholders, if any, within the Section 8(a)(i)
              Acceptance Period.

                        (ii) If the Company shall fail to accept, or shall
              reject in writing, any or all of the Subject Stock offered for
              Sale pursuant to the Section 8 Offer, then, upon the earlier of
              the expiration of the Section 8(a)(i) Acceptance Period or the
              receipt of a written notice of rejection by the Company, each
              Other Stockholder shall have the right and option, for a period
              of 15 days thereafter (but in no event for a period less than 30
              days after the Section 8 Offer Notice is delivered to the
              Stockholders) (the "Section 8(a)(ii) Acceptance Period"), to
              accept all or any part of the Subject Stock so offered and not
              accepted by the Company (the "Refused Stock") at the purchase
              price, in cash, and on the terms stated in the Section 8 Offer
              Notice; provided, however, that if the Section 8 Offer required
              an All or Nothing Sale, such offer and acceptance shall be
              conditioned upon the Other Stockholders purchasing all, but not
              less than all, of the Refused Stock. Such acceptance shall be
              made by delivering a written notice to the Company and the
              Selling Stockholder within the Section 8(a)(ii) Acceptance
              Period specifying the maximum number of shares such Other
              Stockholder will purchase (the "First Offer Shares"). If, upon
              the expiration of the Section 8(a)(ii) Acceptance Period, the
              aggregate amount of First Offer Shares exceeds the amount of
              Refused Stock, the Refused Stock shall be allocated among the
              Other Stockholders as follows: (i) first, each Stockholder shall
              be entitled to purchase up to its proportionate percentage of
              Refused Stock (which proportionate percentage shall equal the
              Stockholder's proportionate percentage ownership of outstanding
              Common Stock) ("Proportionate Percentage"); (ii) second, if any
              shares of Refused Stock have not been allocated for purchase
              pursuant to (i) above (the "Remaining Shares"), each Stockholder
              (an "Oversubscribed Stockholder") which had offered to purchase
              a number of shares of Refused Stock in excess of its
              Proportionate Percentage of Refused Stock pursuant to (i) above,
              shall, for a period of 10 days after receiving
<PAGE>   14
              notice of the existence of the Remaining Shares (the "Remaining
              Share Acceptance Period"), be entitled to purchase an amount of
              Remaining Shares up to its Proportionate Percentage (treating only
              Oversubscribed Stockholders as Stockholders for these purposes) of
              the Remaining Shares; and (iii) third, the process set forth in
              (ii) above shall be repeated with respect to any shares of Refused
              Stock not allocated for purchase until all shares of Refused Stock
              are allocated for purchase. Any Stockholder which does not commit
              to purchase its Proportionate Percentage of Remaining Shares
              during the related Remaining Share Acceptance Period shall not be
              eligible to purchase any more of the Subject Stock in subsequent
              Remaining Share Acceptance Periods in the subject Section 8 Offer.

                        (iii) If effective acceptance shall not be received
              pursuant to Sections 8(a)(i) and 8(a)(ii) above with respect to
              all of the Subject Stock offered for Sale pursuant to the
              Section 8 Offer Notice, then the Selling Stockholder may Sell
              all or any portion of the Stock so offered for Sale and not so
              accepted, at a price not less than the price, and on terms not
              more favorable to the purchaser thereof than the terms, stated
              in the Section 8 Offer Notice at any time within 120 days after
              the expiration of the Section 8(a)(ii) Acceptance Period (or
              such longer period as may be necessary to obtain any required
              regulatory approval, but in no case to exceed 6 months) (the
              "Sale Period"); provided, however, that if the Section 8 Offer
              contemplated an All or Nothing Sale, the Selling Stockholder may
              sell all, but not less than all, of the Subject Stock. To the
              extent the Selling Stockholder Sells all or a portion of the
              Stock so offered for Sale during the Sale Period, the Selling
              Stockholder shall promptly notify the Company, and the Company
              shall promptly notify the Other Stockholders, as to (i) the
              number of shares of Stock, if any, that the Selling Stockholder
              then owns, (ii) the number of shares of Stock that the Selling
              Stockholder has Sold, (iii) the terms of such Sale and (iv) the
              identity of the purchaser(s) of any shares of Stock Sold. In the
              event that all of the Stock is not Sold by the Selling
              Stockholder during the Sale Period, the right of the Selling
              Stockholder to Sell such unsold Stock shall expire and the
              obligations of this Section 8 shall be reinstated; provided,
              however, that, in the event that the Selling Stockholder
              determines, at any time during the Sale Period, that the Sale of
              all of the Stock on the terms set forth in the Section 8 Offer
              Notice is impractical, the Selling Stockholder may terminate the
              offer and reinstate the procedure provided in this Section 8
              without waiting for the expiration of the Sale Period; and
              provided further, however, that the Selling Stockholder shall
              not give a Section 8 Offer Notice with respect to a transaction
              which would require compliance with this Section 8 for a period
              of at least 60 days from the last day of the Sale Period.

                        (iv) In the event that the consideration payable to
              the Selling Stockholder by the third party purchaser is in a
              form other than cash (excluding marketable securities listed
              on a national securities exchange or the Nasdaq National
              Market, the value of which shall be determined by calculation
              of such securities' average price over the 10 trading days
              prior to delivery of the Section 8

<PAGE>   15

              Appraisal Notice (as defined herein)), the Selling Stockholder
              shall deliver notice to the Company and the Other Stockholders
              at least 30 days prior to the closing of the sale of the Subject
              Stock, including information regarding the form of consideration
              payable by the purchaser (the "Section 8 Appraisal Notice"). The
              Company or any of the Other Stockholders shall have the right to
              require the Selling Stockholder to commission, at the Selling
              Stockholder's expense, an appraisal of the value of the non-cash
              consideration acquired by the Selling Stockholder from the third
              party purchaser (the "Section 8 Appraisal"), by delivery of
              written notice of the same within 10 days after the receipt of a
              Section 8 Appraisal Notice. The Selling Stockholder shall use
              its commercially reasonable efforts to complete the Section 8
              Appraisal prior to the expiration of the Sale Period; provided,
              however, that if the Section 8 Appraisal is not completed during
              the original term of the Sale Period, such period shall be
              extended to the date which is 10 days after such Section 8
              Appraisal is completed. If the Section 8 Appraisal (or
              calculation of the value of marketable securities set forth
              above, if applicable) indicates that the value of the non-cash
              consideration payable by the third party purchaser is less than
              the aggregate value of the per share price, as set forth in the
              Section 8 Offer Notice, for all of the Subject Stock, the
              Selling Stockholder shall not sell the Subject Stock to such
              purchaser unless such purchaser pays the difference to the
              Selling Stockholder in the form of cash.

                       (v) All Sales of Subject Stock to the Company or to
              one or more Other Stockholders subject to any Section 8 Offer
              Notice shall be consummated at the offices of Fried, Frank,
              Harris, Shriver & Jacobson, One New York Plaza, New York, New
              York, or at such other place as the parties to such sales may
              agree, on the later of (i) a mutually satisfactory Business
              Day within 20 days after the expiration of the Section 8(a)(i)
              Acceptance Period or the Section 8(a)(ii) Acceptance Period,
              as applicable, or, in the case of Remaining Shares sold in
              multiple rounds, within 10 days after the expiration of the
              last Remaining Share Acceptance Period, or (ii) if applicable,
              the fifth Business Day following the expiration or termination
              of all waiting periods under HSR, or the receipt of any other
              regulatory approvals applicable to such sales, or at such
              other time as the parties to such sales may agree. The
              delivery of certificates or other instruments evidencing such
              Subject Stock duly endorsed for transfer shall be made on such
              date against payment of the purchase price for such Subject
              Stock.

                       (vi) So long as GSCP or any of its Affiliates is the
              Selling Stockholder, without the unanimous consent of the
              Other Stockholders, the Company shall not accept, and shall
              immediately reject, any Section 8 Offer.

                       (vii) In addition to the foregoing procedures, to the
              extent applicable, the provisions of Sections 16 and 17 shall
              apply.

                       (viii) The provisions of this Section 8: (i) shall
              not apply to any Sale of Stock by a Stockholder to an
              Affiliate of such Stockholder, (ii) shall not apply to any
              Sale of Stock by Mitsubishi or its Affiliates to TEPCO
              International or its

<PAGE>   16

              Affiliates or any Sale of Stock by TEPCO International or its
              Affiliates to Mitsubishi or its Affiliates, (iii) shall not
              apply to any Sale of Stock by a Stockholder or its Affiliates in
              an IPO, (iv) shall not apply to any Sale of Stock by COSI or its
              Affiliates to the Company in accordance with the COSI Purchase
              Agreement, (v) shall terminate upon an IPO, and (vi) shall not
              permit the Sale of Stock to an entity which, as a result of such
              entity holding an ownership interest in the Company, would have
              a material adverse regulatory effect on the ability of the
              Company or its subsidiaries or any Stockholder or its Affiliates
              (a) to sell power at market-based rates or (b) to acquire
              additional generating assets in the United States or Canada and
              to sell such power at market-based rates.

                       (b) In connection with any Sale of Stock by a
              Stockholder or its Affiliates, a Selling Stockholder may, but
              shall not be required to, assign to the purchaser of such
              Stock (the "Purchaser") a portion of the Selling Stockholder's
              unfulfilled obligation, as of the time of such Sale, pursuant
              to Section 3(a) of this Agreement, which portion shall not
              exceed the percentage that the number of shares of Stock being
              sold to such Purchaser by the Stockholder and its Affiliates
              bears to the aggregate number of shares of Stock purchased by
              the Stockholder and its Affiliates, as of the time of such
              Sale, pursuant to Section 3 of this Agreement; provided,
              however, no such assignment shall relieve the Selling
              Stockholder from its obligations under this Agreement to
              fulfill such Capital Commitment in full to the extent not
              fulfilled by the Purchaser pursuant to such assignment,
              including as a result of any default by the Purchaser.

                       (c) In the event that, in a transaction or series of
              related or unrelated transactions, GSCP and its Affiliates
              Sell, pursuant to this Section 8, (i) between 40% and 80% of
              the number of shares of Stock of the Company held by it, GSCP
              shall lose its right to designate two of its Designated
              Directors pursuant to Section 6.1 hereof or (ii) more than 80%
              of the number of shares of Stock of the Company held by it,
              (x) GSCP shall lose its right to designate all of its
              Designated Directors pursuant to Section 6.1 hereof and (y)
              GSCP's rights pursuant to Sections 14 and 17 hereof shall be
              of no further force or effect.

                       (d) In the event that, in a transaction or series of
              related or unrelated transactions, (i) Constellation and its
              Affiliates Sell, pursuant to this Section 8, greater than 50%
              of the number of shares of Stock held by it, Constellation
              shall lose its right to designate its Designated Director
              pursuant to Section 6.1 hereof or (ii) Mitsubishi or TEPCO
              International and their respective Affiliates Sell (excluding
              sales to Mitsubishi or TEPCO International or their respective
              Affiliates) greater than 50% of the number of shares of Stock
              held by Mitsubishi and TEPCO International, collectively,
              Mitsubishi and TEPCO International shall lose the right to
              designate their Designated Director and their right to appoint
              the New Investors' Observer pursuant to Section 6.1 hereof.
<PAGE>   17

        Section 9. Stockholder Approval. The consent of the holders of
two-thirds (2/3) of the issued and outstanding shares of
Common Stock shall be required for any of the following actions:

        (a) The Company's redemption or repurchase of any Common Stock or
Preferred Stock in excess of an aggregate amount of $25,000,000, except in
connection with (i) the Company's exercise of its rights pursuant to Section 8
or Section 11 hereof (ii) pursuant to any employment or option agreement to
which the Company is a party, or (iii) pursuant to the COSI Purchase Agreement;

        (b)  Any material amendment or repeal of the Company's Certificate of
Incorporation or By-laws; or

(c) Any material changes to the Company's business of investing in, owning and
operating electric utility assets and related businesses.

Section 10.  PUHCA, FPA and Market-Based Rates

        (a) Each Stockholder agrees with each other Stockholder that it will
not allow the Company to, and the Company agrees that it will not, acquire,
directly or indirectly, any of the voting securities of, nor will it allow the
Company to, and the Company agrees that it will not, become, (i) a
"public-utility company" (as such term is defined in the Public Utility Holding
Company Act of 1935 ("PUHCA") or (ii) an "affiliate" (as such term is defined in
Section 2(a) 11(A) of PUHCA) or a "holding company" (as such term is defined in
PUHCA) with respect to any such public-utility company nor will it allow the
Company to, and the Company agrees that it will not, become a "public utility"
(as such term is defined in the Federal Power Act (the "FPA")), in each case so
long as PUHCA and/or the FPA are in effect and so long as acquiring any such
securities or becoming any of the entities identified above imposes material
regulatory or other restrictions on the Company or the Stockholders.
Notwithstanding the preceding sentence, filings with the Federal Energy
Regulatory Commission to qualify as an "exempt wholesale generator" (as such
term is defined in PUHCA) or a "qualifying facility" (as such term is defined in
the Public Utility Regulatory Policies Act of 1978) or other necessary filings
by the Company or any of its Stockholders to effectuate the acquisition of a
Portfolio Asset shall be permitted.

        Notwithstanding any other provision of this Agreement, each Stockholder
agrees with each other Stockholder, and the Company agrees, that the Company
shall not knowingly sell Stock to any Person if such sale would impose material
regulatory or other restrictions on the Company or any Stockholder under PUHCA.

                        (b) Each Stockholder agrees with each other Stockholder
                that it will not, and will not allow the Company, and the
                Company agrees that it will not: (i) acquire Portfolio Assets
                which acquisition would have a material adverse regulatory
                effect on the ability of the Company, a Stockholder or its
                Affiliates to sell power at market-based rates; (ii) permit a
                Sale of Stock to a Person which Sale would have a material
                adverse regulatory effect on the ability of the Company, a
                Stockholder or its Affiliates to sell power at market-based
                rates; or

<PAGE>   18
                (iii) take any other action which would have a material adverse
                regulatory effect on the ability of the Company, a Stockholder
                or its Affiliates to sell power at market-based rates;
                provided, however, that in connection with any bid or any other
                actions by the Company which would result in any of the actions
                set forth in clauses (i), (ii) and (iii) above, each of the
                Company and each Stockholder will take such reasonable steps
                considering the facts and circumstances, as expeditiously as is
                practicable, as are necessary to structure the proposed
                transaction in order to mitigate the circumstances to avoid any
                material adverse regulatory effect on the ability of the
                Company, such Stockholder or its Affiliates to sell power at
                market-based rates.

Section 11.  Certain Acquisitions of Interests.

        If an interest in any Stockholder, or any of its Affiliates (any such
entity referred to as the "Subject Entity" for purposes of this Section), is
directly or indirectly acquired (an "Acquisition Event") by an entity which, as
a result of such entity holding an ownership interest in the Subject Entity,
would have a material adverse regulatory effect on the ability of the Company or
its subsidiaries or any Stockholder or its Affiliates (A) to sell power at
market-based rates or (B) to acquire additional generating assets in the United
States or Canada and to sell such power at market-based rates (a "Regulatory
Restriction"), then:

                        (a) the Subject Entity, and any applicable Affiliate of
                such Subject Entity, shall attempt to cure ("Cure") the
                Regulatory Restriction by either (i) taking such steps, as
                expeditiously as is practicable, as are necessary to mitigate
                ("Mitigation Efforts") the circumstances to avoid the
                implication of the Regulatory Restriction on the Company
                (including, without limitation, transferring its Stock ownership
                in the Company to an affiliate that, notwithstanding such entity
                holding an ownership interest in the Company, would not impose a
                Regulatory Restriction) or (ii) Selling at least that number of
                shares of Stock, for cash, in a Sale that would avoid the
                implication of the Regulatory Restriction on the Company (a
                "Curing Sale"), in accordance with and subject to the following
                (which provisions, rather than the provisions of Section 8(a)
                hereof, shall govern such Curing Sale):

                        (i) If the Subject Entity shall agree upon the material
                terms of a potential Curing Sale with an entity or group of
                entities (the "Potential Buyer"), the ownership of the Stock to
                be sold in the Curing Sale by which would not cause a Regulatory
                Restriction, the Subject Entity shall, at least 15 days prior to
                the Outside Cure Date (as defined in Section 11(b)), deliver to
                the Company a written notice (a "Section 11 Offer Notice"),
                which shall (a) state the Subject Entity's intention to Sell
                Stock to the Potential Buyer, the identity or identities of the
                Potential Buyer, the amount of Stock intended to be Sold (the
                "Subject Stock"), the proposed purchase price therefor and a
                summary of the other material terms of the potential Curing Sale
                and (b) offer (the "Section 11 Offer") the Company the option to
                purchase for cash, in lieu of the Potential Buyer, the Subject
                Stock at the purchase price set forth in the Section 11 Offer
                Notice. The
<PAGE>   19

                Section 11 Offer shall remain open and irrevocable for a period
                of 10 Business Days after delivery of the Section 11 Offer
                Notice (the "Section 11 Acceptance Period"), during which time
                the Company shall have the right to accept the Section 11 Offer;
                provided that the Subject Entity's Designated Directors shall
                not participate in any vote of the Board as to whether such
                Section 11 offer shall be accepted, except for purposes of
                establishing the requisite quorum for such vote. If a Section 11
                Offer is accepted, the Company shall be irrevocably obligated to
                consummate the purchase as set forth in Section 11(a)(iii)
                below. Such acceptance shall be made by delivering a written
                notice to the Subject Entity within the Section 11 Acceptance
                Period.

                        (ii) If effective acceptance of the Section 11 Offer
                shall not be given as set forth in Section 11(a)(i), then the
                Subject Entity may Sell the Subject Stock, subject to the time
                period set forth in Section 11(b) hereof, at the price and on
                the terms set forth in the Section 11 Offer Notice.

                        (iii) All Sales of Subject Stock to the Company subject
                to any Section 11 Offer Notice shall be consummated at the
                offices of Fried, Frank, Harris, Shriver & Jacobson, One New
                York Plaza, New York, New York, or at such other place as the
                parties may agree, on a mutually satisfactory Business Day
                within the Outside Cure Date (as defined in Section 11(b)
                below.)

                        (b) Notwithstanding any provision contained in this
                Section 11, if the Subject Entity fails to Cure the Regulatory
                Restriction either through Mitigating Efforts or consummating a
                Curing Sale within 30 days after the closing of the Acquisition
                Event (the "Outside Cure Date"), then the Company shall have the
                right (the "Purchase Right"), exercisable by the Company by
                delivering written notice to the Subject Entity within 30 days
                of the Outside Cure Date, to purchase that portion of the Stock
                owned by the Subject Entity which would avoid the imposition of
                a Regulatory Restriction on the Company (such Stock to be
                purchased referred to as the "Company Subject Stock"), in
                accordance with the following:

                                (i) Prior to an initial public offering of the
                Common Stock of the Company, the Company shall have the right to
                purchase the Company Subject Stock from the Subject Entity at a
                price equal to the lesser of (x) the price paid by the Subject
                Entity for the Company Subject Stock ("Cost") (calculated using
                the weighted average price paid per share of all Common Stock
                purchased by the Subject Entity times the number of shares of
                Company Subject Stock) and (y) the Book Value of such Company
                Subject Stock times the number of shares of Company Subject
                Stock.

                                (ii) Subsequent to an initial public offering of
                the Common Stock of the Company, the Company shall have the
                right to purchase the Company Subject Stock from the Subject
                Entity at a price equal to the lower of (a) Cost or (b) Fair
                Market Value. Fair Market Value shall be defined as the average
                of the

<PAGE>   20

                closing sale prices during the 10 trading days immediately
                preceding the date on which the Purchase Right is accepted of a
                share of Stock on the Composite Tape for New York Stock
                Exchange-Listed Stocks, or, if the Stock is not quoted on the
                Composite Tape, on the New York Stock Exchange, or, if the Stock
                is not listed on such exchange, on the principal United States
                securities exchange registered under the Securities Exchange Act
                of 1934, as amended, on which the Stock is listed, or, if the
                Stock is not listed on any such exchange, the average of the
                closing bid quotations with respect to a share of Stock during
                the 10 trading days period preceding the date on which the
                Purchase Right is accepted on the National Association of
                Securities Dealers, Inc. Automated Quotations System or any
                system then in use.

                                (iii) If the Company shall exercise its Purchase
                Right, then the closing of such Purchase Right shall be
                consummated at the offices of Fried, Frank, Harris, Shriver &
                Jacobson, One New York Plaza, New York, New York, within 20 days
                of the date on which the Purchase Right is accepted, or at such
                other place and time as the parties may agree.

Section 12.  Operating Services and Power Sales and Brokering Services

        With respect to each Portfolio Asset, CPS will be the exclusive provider
of power marketing and risk management services pursuant to, and subject to,
that certain Strategic Alliance Agreement between the Company and Constellation,
dated as of March 10, 1998, and any operating agreements entered into
thereunder.

Section 13.  Fees

        In addition to any fees payable to GSCP or any of its Affiliates with
respect to any financing relating to the Company and any fees payable under the
Strategic Alliance Agreements, the Company shall pay in cash to GSCP,
Constellation, DGC and TEPCO International an investment banking fee in
connection with each acquisition of Portfolio Assets by the Company equal to 1%
of the aggregate consideration (including the assignment of debt) paid by the
Company in such acquisition transaction or, in the event such fee, in the view
of GSCP and the Company, is not obtainable, such other amount that is
commercially reasonable in connection with such transaction as is agreed by GSCP
and the Company. Any such investment banking fee shall be paid to GSCP,
Constellation, DGC and TEPCO International on a proportionate percentage (which
proportionate percentage shall equal each of GSCP, Constellation, Mitsubishi and
TEPCO International's respective proportionate percentage ownership of
outstanding Common Stock but without giving effect to any outstanding Common
Stock Equivalents, including warrants).

Section 14.  Investment Banker

        Goldman Sachs will have the right to provide all investment banking
services to the Company. Such services shall be provided on arms-length terms,
conditions and pricing.

<PAGE>   21

        Section 15. Transactions with Affiliates. All transactions after the
date hereof between the Company and the Stockholders or their respective
Affiliates shall be based on arm's length negotiation which result in
market-based price, terms and conditions. The parties hereby agree and
acknowledge that, as of the date hereof, the Company is party to a
Non-Competition Agreement with each of Mitsubishi, TEPCO International and
certain Affiliates of Constellation (Baltimore Gas & Electric Company and
Constellation Power, Inc.).

                Section 16. Tag-Along and Change of Control Rights. (a) Subject
to Section 16(d) below, prior to an IPO, in the event that, following compliance
with the provisions of Section 8 hereof, a Stockholder proposes to Sell (a
"Disposition") (other than pursuant to an IPO) any Stock to a Person other than
an Affiliate of such Stockholder and other than to the Other Stockholders (a
"Purchaser") then such party (the "Proposing Holder") shall provide notice (a
"Proposal Notice") of such proposed Disposition to the Other Stockholders no
later than twenty (20) days prior to the proposed closing of such Disposition
(which 20 day period may run concurrently with the periods set forth in Section
8, to the extent applicable). Each Proposal Notice shall describe in reasonable
detail the terms of the proposed Disposition, including, without limitation, (i)
the identity and address of the Purchaser, (ii) the proposed amount to be paid
by the Purchaser to the Proposing Holder, (iii) the amount and type of Stock
proposed to be Sold and (iv) any other material terms or conditions of such
proposed Disposition, and shall include a statement to the effect that the
Purchaser has been informed of the Tag-Along Rights (as defined herein) and an
acknowledgment by the Purchaser indicating that it has been so informed and
agrees to such terms. A copy of the Proposal Notice shall promptly be sent to
the Company.

                (b) Subject to Sections 16(c) and 16(d) below, with respect to
each proposed Disposition, prior to an IPO, the Stockholders shall have the
following right (the "Tag-Along Right"): each Other Stockholder shall have the
right to require the Purchaser to purchase from such Other Stockholder and at
the Disposition Price (as defined below) all or a portion of the number of
shares of Common Stock which represents the number of shares of Common Stock
obtained by multiplying (A) a fraction, the numerator of which is the number of
shares of Common Stock represented by the Stock proposed to be Sold (as
indicated in the Proposing Notice) and the denominator of which is the number of
shares of Common Stock Beneficially Owned by the Proposing Holder as of the date
of the Proposal Notice, times (B) the number of shares of Common Stock
Beneficially Owned by the Other Stockholder as of the date of the Proposal
Notice.

                (c) If the Purchaser declines to purchase all of the shares of
Common Stock of the Proposing Holder and each Other Stockholder to be sold
pursuant to Section 16(b) hereof, then each Other Stockholder shall have the
right to require the Purchaser to purchase from such Other Stockholder and at
the Disposition Price all or a portion of the number of shares of Common Stock
which represents the number of shares of Common Stock obtained by multiplying
(A) a fraction, the numerator of which is the number of shares of Common Stock
represented by the Stock proposed to be Sold (as indicated in the Proposing
Notice) and the denominator of which is the number of shares of Common Stock
Beneficially Owned by all of the Stockholders as of the date of the Proposal
Notice, times (B) the number of shares of Common Stock Beneficially Owned by
such Other Stockholder as of the date of the Proposal

<PAGE>   22

Notice. The number of shares sold by the Proposing Holder shall be reduced to
the extent any of the Other Stockholders choose to exercise their rights under
this Section.

                (d) The provisions of this Section 16 shall not apply to Sales
of Stock from (i) Mitsubishi and/or its Affiliates to TEPCO International and/or
its Affiliates or to Sales of Stock from TEPCO International and/or its
Affiliates to Mitsubishi and/or its Affiliates, or (ii) COSI to the Company, in
accordance with the COSI Purchase Agreement.

                (e) For purposes of this Agreement, the following terms shall
have the meanings set forth below: "Disposition Price" shall mean (i) with
respect to a share of Common Stock, the Per Share Price and (ii) with respect to
a Common Stock Equivalent, an amount substantially equal to the Per Share Price
taking into account the nature of the Common Stock Equivalent, including its
exercise price, if applicable.

                "Per Share Price" shall mean an amount equal to the quotient
obtained by dividing (i) the aggregate purchase price to be paid by the
Purchaser in respect of such Stock by (ii) the number of shares of Common Stock
proposed to be sold by the Proposing Holder as set forth in the Proposal Notice.

                (f) Each Stockholder electing to exercise its Tag-Along Rights
shall give written notice of its election to the Proposing Holder no later than
twenty (20) days after its receipt of a Proposal Notice (the "Expiration Date").

                (g) All Sales of Stock to the Purchaser shall be consummated
contemporaneously at the offices of Fried, Frank, Harris, Shriver & Jacobson,
One New York Plaza, New York, New York, 10004 on the later of (i) a mutually
satisfactory Business Day as soon as practicable, but not more than 60 days
after the Expiration Date, or such longer period as may be necessary to obtain
any required regulatory approval, but in no case to exceed 6 months or (ii) the
fifth Business Day following the expiration or termination of all waiting
periods under HSR applicable to such Sales, or at such other time and/or place
as the parties to such Sales may agree. The delivery of certificates or other
instruments evidencing such Stock duly endorsed for transfer shall be made on
such date against payment of the purchase price for such Stock.

                Section 17. Bring-Along Rights. (a) If, at any time prior to an
IPO, so long as (i) the Stock Beneficially Owned by GSCP and its Affiliates
constitutes at least 35% of the outstanding Common Stock of the Company, (ii)
GSCP is the largest stockholder of Common Stock of the Company (provided that
Mitsubishi and TEPCO International will be treated as a single stockholder for
such purpose) and (iii) GSCP and its Affiliates have previously Sold no more
than 60,000 shares of Common Stock other than to GSCP or Affiliates of GSCP, in
the event that, following compliance with the provisions of Section 8 hereof,
GSCP shall propose to Sell for cash in a single Sale (including a series of
transactions pursuant to a single agreement) to any single Person (including
Affiliates of such Person) who is not Affiliated with GSCP and its Affiliates (a
"Non-Affiliated Party"), all of its Stock Beneficially Owned by it and its
Affiliates and, immediately following the consummation of such Sale, such
Non-Affiliated Party shall Beneficially Own 50% or more in aggregate of the then
outstanding Common Stock (excluding

<PAGE>   23

any Common Stock purchased by the Non-Affiliated Party as a result of GSCP's
exercise of its rights pursuant to this Section 17) (any such transaction being
referred to herein as an "Exit Sale"), then GSCP shall use its commercially
reasonable efforts to cause the Non-Affiliated Party to submit two bids to the
Stockholders as follows: (i) a bid (including purchase price) for the purchase
of all of the Stock Beneficially owned by the Stockholders and their Affiliates
(the "Whole Company Bid") and (ii) a bid (including purchase price) for the
purchase of all of the Stock Beneficially owned by the Stockholders and their
Affiliates, excluding Mitsubishi, TEPCO International and their respective
Affiliates (the "Partial Company Bid").

                (b) If the price per share to be paid in the Partial Company Bid
is less than the price per share to be paid in the Whole Company Bid, GSCP, in
its sole discretion, may elect to require all of the Stockholders and their
respective Affiliates to Sell all, but not less than all, of the Stock
Beneficially Owned by each of them concurrently with such Exit Sale to such
Non-Affiliated Party at the same purchase price per share (and, in the case of
Common Stock Equivalents, such purchase price per share net of any exercise
price multiplied by the number of shares of Common Stock issuable upon the
conversion, exchange or exercise of such Common Stock Equivalent) and upon the
same terms and subject to the conditions of the Exit Sale as set forth in the
Whole Company Bid. If the price per share to be paid in the Partial Company Bid
is equal to or greater than the price per share to be paid in the Whole Company
Bid, GSCP, in its sole discretion, may elect to require the Stockholders and
their respective Affiliates (excluding Mitsubishi, TEPCO International and their
respective Affiliates, provided that Mitsubishi and TEPCO International and
their respective Affiliates may exercise their rights under Section 16 with
respect to any Sale by the Other Stockholders and their Affiliates) to Sell all
of the Stock Beneficially Owned by each of them concurrently with such Exit Sale
to such Non-Affiliated Party at the same purchase price per share (and, in the
case of Common Stock Equivalents, such purchase price per share net of any
exercise price multiplied by the number of shares of Common Stock issuable upon
the conversion, exchange or exercise of such Common Stock Equivalent) and upon
the same terms and subject to the conditions of the Exit Sale as set forth in
the Partial Company Bid.

                (c) Until the earlier of (i) an IPO, (ii) April 30, 2001 and
(iii) the date which is thirty (30) days after the Company's delivery to the
Stockholders of an audited balance sheet of the Company and its subsidiaries as
at December 31, 2000 and audited statements of operations, cash flow and
stockholders' equity for the fiscal year then ended, if the price per share
payable in the Exit Sale to Mitsubishi and TEPCO International pursuant to a
Whole Company Bid as to which GSCP has made the election set forth in the first
sentence of Section 17(b) is more than $1,000 but less than $1,550, the price
per share payable to GSCP and Constellation in excess of $1,000 shall be reduced
by an amount, allocated and paid to Mitsubishi and TEPCO International, such
that the price per share payable to Mitsubishi and TEPCO International is equal
to $1,550; provided, however, that a portion of the price per share payable
after giving effect to the allocation described above to GSCP and Constellation
shall only be allocated to Mitsubishi and TEPCO International to the extent that
such allocation does not reduce the price per share payable to GSCP and
Constellation below $1,000. This Section 17(c) shall not apply to any Sale by
GSCP to (i) Mitsubishi or its Affiliates or (ii) TEPCO International or its
Affiliates, nor shall this Section 17(c) apply to any Person (or any of its
Affiliates) who has purchased shares of Common Stock from Mitsubishi, TEPCO
International

<PAGE>   24

or their respective Affiliates (the "Previously Sold Shares") with respect to
such Previously Sold Shares.

                (d) The rights set forth in Section 17(a) shall be exercised by
giving written notice (the "Section 17 Notice") to each Stockholder setting
forth in detail the terms of the proposed Sale and the proposed closing date of
the Exit Sale, which proposed date shall not be less than 15 or more than 60
days after such Section 17 Notice is delivered to the Stockholders.

                (e) All Sales of Stock to the Non-Affiliated Party pursuant to
this Section 17 shall be consummated contemporaneously at the offices of Fried,
Frank, Harris, Shriver & Jacobson, One New York Plaza, New York, New York, 10004
on the later of (i) a Business Day not less than 15 or more than 60 days after
the Section 17 Notice is delivered to the Stockholders or (ii) the fifth
Business Day following the expiration or termination of all waiting periods
under HSR applicable to such Sales, or at such other time and/or place as the
parties to such Sales may agree. The delivery of certificates or other
instruments evidencing such Stock duly endorsed for transfer shall be made on
such date against payment of the purchase price for such Stock.

                (f) The availability or exercise of GSCP's rights (or failure to
exercise GSCP's rights) under this Section does not affect the right of the
Other Stockholders to exercise their rights under Section 16 herein after GSCP's
exercise of its rights under this Section (or failure to exercise GSCP's
rights).

Section 18.      Publicity

        The transactions contemplated by this Agreement shall be kept
confidential until made public by means of a press release. The press release
(together with any associated communication materials relating to the
Stockholders and the Company) and (subject to the next sentence) all other
disclosures related to this Agreement and its terms and the transactions
contemplated hereby which differ in any material manner from prior approved
disclosures shall be agreed upon by all of the Stockholders. The press release
shall be released promptly upon the agreement of the parties hereto.

Section  19.     Legend. Each Stockholder and the Company shall take all such
        action necessary to cause each certificate representing outstanding
        shares of Stock owned by a Stockholder to bear a legend containing the
        following (or substantially similar) words:

                "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN
                REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE
                "ACT"). THE SECURITIES HAVE BEEN ACQUIRED FOR INVESTMENT AND MAY
                NOT BE OFFERED, SOLD, PLEDGED, EXCHANGED, TRANSFERRED OR
                OTHERWISE DISPOSED OF EXCEPT IN COMPLIANCE WITH THE ACT."

                "IN ADDITION, THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE
                SUBJECT TO THE RESTRICTIONS ON TRANSFER AND VOTING SET FORTH IN
                THE

<PAGE>   25

                  STOCKHOLDERS' AGREEMENT DATED AS OF APRIL 26, 2000, AS
                  AMENDED FROM TIME TO TIME, BY AND AMONG ORION POWER  HOLDINGS,
                  INC. (THE "COMPANY") AND THE PARTIES THERETO, COPY OF WHICH
                  IS ON FILE IN THE OFFICE OF THE COMPANY."

        The requirement that the above securities legend be placed upon
certificates evidencing shares of Stock shall cease and terminate upon the
earliest of the following events: (i) when such shares are transferred in an
underwritten public offering, (ii) when such shares are transferred pursuant to
Rule 144 under the Securities Act or (iii) when such shares are transferred in
any other transaction if the seller delivers to the Company an opinion of its
counsel, which counsel and opinion shall be reasonably satisfactory to the
Company, or a "no-action" letter from the staff of the Securities and Exchange
Commission, in either case to the effect that such legend is no longer necessary
in order to protect the Company against a violation by it of the Securities Act
upon any sale or other disposition of such shares without registration
thereunder. The requirement that the above legend regarding this Agreement be
placed upon certificates evidencing shares of Stock shall cease and terminate
upon the Sale of such shares of Stock pursuant to a Public Sale. Upon the
consummation of any event requiring the removal of a legend hereunder, the
Company, upon the surrender of certificates containing such legend, shall, at
its own expense, deliver to the holder of any such shares as to which the
requirement for such legend shall have terminated, one or more new certificates
evidencing such shares not bearing such legend.

Section 20.       Representations and Warranties.

         (a)      Each party hereto represents and warrants to the other parties
         hereto as follows:

                  (i)  It has full power and authority to execute, deliver and
         perform its obligations under this Agreement.

                  (ii) This Agreement has been duly and validly authorized,
         executed and delivered by it, and constitutes a valid and binding
         obligation of it, enforceable against it in accordance with its terms
         except to the extent that enforceability may be limited by bankruptcy,
         insolvency or other similar laws affecting creditors' rights generally.

                  (iii) The execution, delivery and performance of this
         Agreement by it does not (x) violate, conflict with, or constitute a
         breach of or default under its organizational documents, if any, or any
         material agreement to which it is a party or by which it is bound or
         (y) violate any law or regulation applicable to it and material to it,
         or any order, writ, judgment, injunction or decree applicable to it.

                  (iv) No consent or approval of, or filing with, any
         governmental or regulatory body, other than the filings which may be
         required by (i) any Stockholder under HSR, in connection with any such
         Stockholder's satisfaction of its Capital Commitments hereunder and/or
         the acquisition of a Portfolio Asset, and (ii) the Federal Energy
         Regulatory Commission and/or applicable regulatory bodies, is required
         to be obtained or made by it in connection with the transactions
         contemplated hereby.
<PAGE>   26

                  (v) It is not a party to any agreement which is inconsistent
         with the rights of any party hereunder or otherwise conflicts with the
         provisions hereof.

Section 21.       Duration of Agreement.

        Subject to Section 8(b), the rights and obligations of a Stockholder
under this Agreement shall terminate at such time as such Stockholder no longer
is the beneficial owner of any shares of Stock. All terms of this Agreement
shall survive until, by their respective terms, they are no longer operative,
except that the terms of Sections 3, 4, 6.1, 6.2, 6.3, 6.5, 6.6, 7, 8, 9, 10,
12, 13 and 14 shall terminate upon the consummation of an IPO.

Section 22.       Further Assurances

        At any time or from time to time, the parties agree to cooperate with
each other, and at the request of any other party, to execute and deliver any
further instruments or documents and to take all such further action as the
other party may reasonably request in order to evidence or effectuate the
consummation of the transactions contemplated hereby and to otherwise carry out
the intent of the parties hereunder.

Section 23.       Amendment and Waiver

        Except as otherwise provided herein, no modification, amendment or
waiver of any provision of this Agreement shall be effective against the Company
or any Stockholder unless such modification, amendment or waiver is approved in
writing by the Company, GSCP, Constellation, Mitsubishi and TEPCO International.
The failure of any party to enforce any of the provisions of this Agreement
shall in no way be construed as a waiver of such provisions and shall not affect
the right of such party thereafter to enforce each and every provision of this
Agreement in accordance with its terms.

Section 24.       Severability.

        Whenever possible, each provision of this Agreement shall be interpreted
in such manner as to be effective and valid under applicable law, but if any
provision of this Agreement is held to be invalid, illegal or unenforceable in
any respect under any applicable law or rule in any jurisdiction, such
invalidity, illegality or unenforceability shall not affect any other provision
or any other jurisdiction, but this Agreement shall be reformed, construed and
enforced in such jurisdiction as if such invalid, illegal or unenforceable
provision had never been contained herein.

Section 25.       Entire Agreement.

           This Agreement and the other writings referred to herein or delivered
pursuant hereto which form a part hereof contain the entire agreement and
understanding among the parties hereto with respect to the subject matter hereof
and supersedes and preempts any prior understandings, agreements or
representations by or among the parties, written or oral, which may have related
to the subject matter hereof in any way.

<PAGE>   27

Section 26.       Successors and Assigns.

        Except as otherwise provided herein, this Agreement shall bind and inure
to the benefit of and be enforceable by the Company and its successors and
assigns and each Stockholder and their respective successors, assigns, heirs and
personal representatives, so long as they hold Stock. Except pursuant to a Sale
of Stock in compliance with Section 8, no Stockholder shall have the right to
assign its rights and obligations under this Agreement, without the consent of
each of the other Stockholders; provided that each of GSCP, Constellation, DGC,
DCI, MIC and TEPCO International may transfer and assign all or part of its
rights and obligations under this Agreement to one or more of its Affiliates
without the consent of the Company and all of the Stockholders. Upon any such
assignment, such assignee shall have and be able to exercise all rights of the
assigning Stockholder and shall be subject to all of the obligations of such
assigning Stockholder. Notwithstanding anything herein to the contrary, GSCP
shall have no right to assign its rights under Section 17 hereof to any party
other than an Affiliate.

         Section 27.  Reserved.

Section 28.       Counterparts.

        This Agreement may be executed in separate counterparts each of which,
when executed and delivered, shall be an original and all of which taken
together shall constitute one and the same agreement.

Section 29.       Remedies.

        Each Stockholder shall be entitled to enforce its rights under this
Agreement specifically to recover damages by reason of any breach of any
provision of this Agreement and to exercise all other rights existing in their
favor. The parties hereto agree and acknowledge that money damages may not be an
adequate remedy for any breach of the provisions of this Agreement and that each
party may in its sole discretion apply to any court of law or equity of
competent jurisdiction for specific performance and/or injunctive relief
(without posting a bond or other security) in order to enforce or prevent any
violation of the provisions of this Agreement.

Section 30.  Notices.

        Any notice provided for in this Agreement shall be in writing and shall
be either personally delivered or sent by facsimile or reputable overnight
courier service (charges prepaid) to the Company, GSCP, Constellation, COSI,
DGC, DCI, MIC and TEPCO International at the addresses set forth below and to
any subsequent holder of Stock subject to this Agreement at such address as the
Company maintains on its books and records, or at such address or to the
attention of such other person as the recipient party has specified by prior
written notice to the sending party. Notices will be deemed to have been given
hereunder when delivered personally or on receipt.

<TABLE>
<S>                                     <C>
     The Company's address is:          Orion Power Holdings, Inc.

                                        7 East Redwood Street
</TABLE>
<PAGE>   28
<TABLE>
<S>                                    <C>
                                        10th Floor

                                        Baltimore, Maryland  21202

                                        Facsimile:  (410) 234-0994

                                        Attention:  General Counsel

                                        with a copy to:

                                        Fried, Frank, Harris, Shriver & Jacobson

                                        One New York Plaza

                                        New York, New York  10004

                                        Facsimile: (212) 859-4000

                                        Attention: Paul M. Reinstein, Esq.
<CAPTION>

         GSCP's address is:  GS Capital Partners II, L.P.
85 Broad Street
New York, New York 10004
Facsimile: (212) 902-3000
Attention: Ben Adler, Esq.

<S>                                     <C>
         Constellation's address is:    111 Market Place

                                        Suite 500

                                        Baltimore, Maryland 21202

                                        Facsimile:  (410) 468-3499

                                        Attention:   David M. Perlman, Esq.

         COSI's address is:             Constellation Operating Services, Inc.

                                        111 Market Place, Suite 200

                                        Baltimore, Maryland  21202

                                        Facsimile:  (410) 230-4849

                                        Attention:  Secretary

</TABLE>

<PAGE>   29
<TABLE>
<S>                                     <C>

         DGC's address is:              Diamond Generating Corporation

                                        333 S. Grand Avenue, Suite 3000

                                        Los Angeles, California 90071

                                        Facsimile:  213-620-1170

                                        Attention:  President

                                        with a copy to:

             Mitsubishi Corporation

         6-3, Marunouchi 2-chome,
         Chiyoda-ku
                                        Tokyo 100-8086, Japan

                                        Facsimile:  81-3-3210-4246

                                        Attention:  Power & Traffic Project

               Development Department

                                        with a copy to:

                                        Morgan, Lewis & Bockius LLP

                                        300 S. Grand Avenue, 22nd Floor

                                        Los Angeles, California 90071

                                        Facsimile:  (213) 612-2554

                                        Attention:  Richard A. Shortz, Esq.

         DCI's address is:              Diamond Cayman, Inc.

         c/o Mitsubishi Corporation
</TABLE>

<PAGE>   30

<TABLE>
<S>                                     <C>
         6-3, Marunouchi 2-chome,
         Chiyoda-ku

                                        Tokyo 100-8086, Japan

                                        Facsimile:  81-3-3210-4246

                                        Attention:  MC/TOK (MD-B)

                                        with a copy to:

                                        Morgan, Lewis & Bockius LLP

                                        300 S. Grand Avenue, 22nd Floor

                                        Los Angeles, California 90071

                                        Facsimile:  (213) 612-2554

                                        Attention:  Richard A. Shortz, Esq.

         MIC's address is:              Mitsubishi International Corporation

                                        520 Madison Avenue

                                        New York, New York

                                        Attention:  Legal Department

                                        Facsimile:  212-605-1771

                                        with a copy to:

                                        Morgan, Lewis & Bockius LLP

                                        300 S. Grand Avenue, 22nd Floor

                                        Los Angeles, California 90071

                                        Facsimile:  (213) 612-2554
</TABLE>
<PAGE>   31

<TABLE>
<S>                                         <C>

                                             Attention:  Richard A. Shortz, Esq.

TEPCO International's address is:            Tokyo Electric Power Company

  International B.V.

  Officia 1, De Boelelaan 7, 1083HJ

  Amsterdam, The Netherlands

  Facsimile:  31-20-642-7675

  Attention:  BTM Trust (Holland) B.V.

  with a copy to:

  The Tokyo Electric Power Co., Inc.

  1-3 Uchisaiwai-cho 1-chome Chiyoda-ku

  Tokyo 100-0011 Japan

  Facsimile:  81-3-3596-8438

  Attention:  Business Development Group

International Affairs Department

        with a copy to:

        Morgan, Lewis & Bockius LLP

                                             300 S. Grand Avenue, 22nd Floor

                                             Los Angeles, California 90071

                                             Facsimile:  (213) 612-2554

                                             Attention:  Richard A. Shortz, Esq.
</TABLE>
<PAGE>   32

Section 31.      Governing Law; Submission to Jurisdiction; Waiver of Jury Trial

        This Agreement shall be governed by and construed in accordance with the
laws of the State of New York without giving effect to the principles of
conflicts of law. Each of the parties hereto hereby irrevocably and
unconditionally consents to submit to the exclusive jurisdiction of the courts
of the State of New York and of the United States of America, in each case
located in the County of New York, for any action, proceeding or investigation
in any court or before any governmental authority ("Litigation") arising out of
or relating to this Agreement and the transactions contemplated hereby (and
agrees not to commence any Litigation relating thereto except in such courts),
and further agrees that service of any process, summons, notice or document by
U.S. registered mail to its respective address set forth in this Agreement shall
be effective service of process for any Litigation brought against it in any
such court. Each of the parties hereto hereby irrevocably and unconditionally
waives any objection to the laying of venue of any Litigation arising out of
this Agreement or the transactions contemplated hereby in the courts of the
State of New York or the United States of America, in each case located in the
County of New York, and hereby further irrevocably and unconditionally waives
and agrees not to plead or claim in any such court that any such Litigation
brought in any such court has been brought in an inconvenient forum. Each of the
parties irrevocably and unconditionally waives, to the fullest extent permitted
by applicable law, any and all rights to trial by jury in connection with any
Litigation arising out of or relating to this Agreement or the transactions
contemplated hereby.

Section 32.       Descriptive Headings.

        The descriptive headings of this Agreement are inserted for convenience
only and do not constitute a part of this Agreement.

Section 33.       Construction.

        Where specific language is used to clarify by example a general
statement contained herein, such specific language shall not be deemed to
modify, limit or restrict in any manner the construction of the general
statement to which it relates. The language used in this Agreement shall be
deemed to be the language chosen by the parties hereto to express their mutual
intent, and no rule of strict construction shall be applied against any party.

Section 34.       Survival of Representations and Warranties.

        All representations and warranties contained in this Agreement or made
in writing by any party in connection herewith shall survive the execution and
delivery of this Agreement and the consummation of the transactions contemplated
hereby regardless of any investigation made by, or on behalf of, any
Stockholder.

Section 35.       No Inconsistent Agreements.

        Neither the Company nor any Stockholder shall take any action or enter
into any agreement which is inconsistent with the rights of any party hereunder
or otherwise conflicts with the provisions hereof.

<PAGE>   33

Section 36.       Conflicting Agreements.

        Each Stockholder represents and warrants that such Stockholder has not
granted and is not a party to any proxy, voting trust or other agreement which
is inconsistent with or conflicts with any provision of this Agreement, and no
holder of Stock shall grant any proxy or become party to any voting trust or
other agreement which is inconsistent with or conflicts with any provision of
this Agreement.

         Section 37. Confidentiality. The Company and the parties hereto shall
keep the existence and the terms of any non-competition agreement between the
Company and any of the parties hereto strictly confidential unless (i) the
disclosing party has received the advice of independent counsel that such
disclosure is required by any law (including, without limitation, any judicial
order) or other requirement of any governmental entity to which the disclosing
party is subject (provided that prior to such disclosure, the disclosing party
promptly advises and consults with the non-disclosing parties concerning the
information it proposes to disclose), (ii) the disclosing party discloses such
information to a potential purchaser of Company equity held by the disclosing
party (provided that prior to such disclosure, the potential purchaser executes
a confidentiality agreement imposing confidentiality obligations on such
potential purchaser with respect to any non-competition agreement substantially
identical to the confidentiality obligations imposed by this Section 37) or
(iii) such information becomes publicly available (other than as a result of any
act or omission by such disclosing party; provided that any disclosure by a
party in breach of this Section 37 that results in information becoming publicly
available shall not be excused).

        IN WITNESS WHEREOF, the parties hereto have executed this Second Amended
and Restated Stockholders' Agreement on the day and year first above written.

                                ORION POWER HOLDINGS, INC.

                                By:

                                     Name:
                                     Title:

                                GS CAPITAL PARTNERS II, L.P.

                                By:  GS Advisors, L.P., its general partner
                                By:  GS Advisors, Inc., its general partner

                                By:

                                CONSTELLATION ENTERPRISES, INC.

<PAGE>   34

               By:

                      Name:  C. W. Shivery
                      Title: President and Chief Executive Officer

               CONSTELLATION OPERATING SERVICES, INC.

                By:

                      Name:
                      Title:

               OTHER GS ENTITIES

               GS CAPITAL PARTNERS III, L.P.

               By:  GS Advisors III, L.P., its general partner
               By:  GS Advisors III, Inc., its general partner

               By:

               STONE STREET FUND 1998, L.P.

               By:    Stone Street Advantage Corp., its general partner

               By:
                      ---------------------------------
                      Name:

                      Title:

               BRIDGE STREET FUND 1998, L.P.

<PAGE>   35

                By:    Stone Street Advantage Corp., its managing general
                       partner
                By:
                       ---------------------------------
                       Name:

                       Title:

                BRIDGE STREET FUND 2000, L.P.

                By:

                By:
                       ------------------------------
                       Name:

                       Title:

                STONE STREET FUND 2000, L.P.

                By:

                By:
                       -----------------------------
                       Name:

                       Title:

                GS CAPITAL PARTNERS II OFFSHORE, L.P.

                By:    GS Advisors II (Cayman), L.P., its general partner

                By:    GS Advisors II, Inc., its general partner

                By:

                       Name:
                       Title:

                GS CAPITAL PARTNERS III OFFSHORE, L.P.

<PAGE>   36
                By:    GS Advisors III (Cayman), L.P., its general partner

                By:    GS Advisors III, Inc., its general partner

                By:

                       Name:
                       Title:

                GOLDMAN, SACHS & CO. VERWALTUNGS GmbH
                (as nominee for GS Capital Partners II Germany C.L.P.)

                By:

                       Name:
                       Title:

                and

                By:

                       Name:
                       Title:

                GOLDMAN, SACHS & CO. VERWALTUNGS GmbH
                (as nominee for GS Capital Partners III Germany C.L.P.)

                By:

                       Name:
                       Title:

                and

                By:

                       Name:
                       Title:

                DIAMOND GENERATING CORPORATION

By:
<PAGE>   37

         Name:

          Title:

DIAMOND CAYMAN, INC.

By:

         Name:

          Title:

MITSUBISHI INTERNATIONAL CORPORATION

By:

         Name:

          Title:

TOKYO ELECTRIC POWER COMPANY INTERNATIONAL B.V.

By:

         Name:

          Title:

                                                        Exhibit 10.27

                                     ANNEX A
                                     -------
<TABLE>
<CAPTION>
                                                          OWNERSHIP PERCENTAGE
                                                        ------------------------
<S>                                                      <C>
Constellation                                            27.322%

</TABLE>

<PAGE>   38

<TABLE>
<S>                                                      <C>
GSCP                                                     55.232%
Mitsubishi                                               10.468%
TEPCO International                                      6.978%
</TABLE>

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