<PAGE>

                                                                   Exhibit 10(c)

                                                                  CONFORMED COPY


                                   AMENDMENT
                              TO CREDIT AGREEMENT


     This AMENDMENT, dated as of February 23, 2001 (this "Amendment"), is made
to that certain FIVE-YEAR SECOND AMENDED AND RESTATED COMPETITIVE ADVANCE AND
REVOLVING CREDIT FACILITY AGREEMENT, dated as of February 25, 2000 (the "Credit
Agreement"), among TEXAS UTILITIES COMPANY, a Texas corporation doing business
as TXU Corp. ("TXU"); TXU ELECTRIC COMPANY, a Texas corporation and a wholly
owned subsidiary of TXU ("TXU Electric"), and TXU GAS COMPANY, a Texas
corporation and a wholly owned subsidiary of TXU ("TXU Gas" and, together with
TXU and TXU Electric, the "Borrowers", and each individually, a "Borrower"); the
Lenders party thereto (the "Lenders"); and THE CHASE MANHATTAN BANK ("Chase"),
as Competitive Advance Facility Agent (in such capacity, the "CAF Agent"), as
administrative agent for the Lenders (in such capacity, the "Administrative
Agent"; and, together with the CAF Agent, the "Agents") and as fronting bank for
the Letters of Credit issued thereunder (in such capacity, the "Fronting Bank").

                            PRELIMINARY STATEMENT:

     The Borrowers, the Lenders, the Agents and the Fronting Bank previously
entered into the Credit Agreement.  The Borrowers have requested that the
Lenders, the Agents and the Fronting Bank agree to the amendment of the Credit
Agreement as set forth herein and the Lenders, the Agents and the Fronting Bank
have agreed to such request, subject to the terms and conditions of this
Amendment.  Therefore, for good and valuable consideration, the receipt and
adequacy of which are hereby acknowledged, the parties agree as follows:

     SECTION 1. Definitions. Capitalized terms used but not defined herein have
the meanings assigned to such terms in the Credit Agreement.

     SECTION 2. Amendments. Subject to the satisfaction of the conditions
precedent set forth in Section 3 hereof, the Credit Agreement is hereby amended
as follows:

     (a)  The definition of "Facility A Credit Agreement" set forth in Section
1.01 of the Credit Agreement is hereby amended and restated in its entirety to
read as follows:

          "Facility A Credit Agreement" shall mean the 364-Day Competitive
     Advance and Revolving Credit Facility Agreement, dated as of February 23,
     2001, among the Borrowers and certain other parties named therein, as
     amended, modified or supplemented from time to time.
<PAGE>

                                                                               2

     (b)  The definition of "LC Commitment Amount" set forth in Section 1.01 of
the Credit Agreement is hereby amended and restated in its entirety to read as
follows:

          "LC Commitment Amount" shall mean $500,000,000.

     (c)  The definition of "U.K. Facility Agreement" set forth in Section 1.01
of the Credit Agreement is hereby amended and restated in its entirety to read
as follows:

          "U.K. Facility Agreement" shall mean the Facilities Agreements, dated
     August 23, 2000, with respect to a (Pounds)750 million term facility, a
     (Pounds)325 million revolving credit facility and a (Pounds)300 million
     revolving credit facility, among TXU Europe Limited, the lenders parties
     thereto and certain other parties named therein, as amended, modified or
     supplemented from time to time.

     (d)  Clause (iii) of Section 2.01 of the Credit Agreement is hereby amended
and restated in its entirety to read as follows:

          (iii) unless and until the TXU Electric Approval Date shall have
     occurred, at no time shall the sum of (x) the outstanding aggregate
     principal amount of all Loans made to TXU Electric plus (y) the outstanding
     aggregate principal amount of all "Loans" under and as defined in the
     Facility A Credit Agreement made to TXU Electric plus (z) the aggregate
     amount of LC Outstandings for the account of, or owing by, TXU Electric
     exceed $2,000,000,000,

     (e)  Section 3.14 ("Year 2000 Compliance") and all references thereto are
deleted.

     SECTION 3. Conditions of Effectiveness. Section 2 of this Amendment shall
become effective as of the date first set forth above (the "Amendment Date")
when each of the following conditions shall have been fulfilled:

          (i)  the Agents, the Fronting Bank, the Required Lenders and the
     Borrowers shall each have executed and delivered to the Administrative
     Agent a counterpart of this Amendment;

          (ii) the following statements shall be true and correct and the
     Administrative Agent shall have received a certificate of a duly authorized
     officer of TXU, dated the Amendment Date and in sufficient copies for each
     Lender, stating that:

               (A)  the representations and warranties of each Borrower set
          forth in Section 4 hereof are true and correct on and as of the
          Amendment Date as though made on and as of such date; and
<PAGE>

                                                                               3

               (B)  no event has occurred and is continuing that constitutes a
          Default or an Event of Default;

          (iii)  the Administrative Agent shall have received the following,
each dated the Amendment Date, in form and substance satisfactory to the
Administrative Agent and in sufficient copies for each Lender:

               (A)  certified copies of the resolutions of the Board of
          Directors of each of the Borrowers approving the execution and
          delivery by such Borrower of this Amendment and the performance by
          such Borrower of its obligations under the Credit Agreement as amended
          hereby, and of all documents evidencing other necessary corporate
          action with respect to the execution and delivery by such Borrower of
          this Amendment and the performance by such Borrower of its obligations
          under the Credit Agreement as amended hereby;

               (B)  a certificate of the Secretary or an Assistant Secretary of
          each of the Borrowers certifying:

                    (1)  the names, true signatures and incumbency of the
               officers of such Borrower authorized to sign this Amendment; and

                    (2)  that neither the certificate of incorporation (or
               comparable charter document) nor the bylaws of such Borrower have
               been amended, supplemented or otherwise modified since February
               25, 2000 or, if either such document has been amended,
               supplemented or modified since such date, that attached thereto
               is a true, correct and complete copy of such document as of the
               Amendment Date;

               (C)  a certificate of a Responsible Officer of each Borrower
          certifying that all actions, consents, authorizations or approvals of,
          registrations or filings with, or other actions by, any Governmental
          Authority required in connection with the execution and delivery by
          such Borrower of this Amendment and the performance by such Borrower
          of its obligations under the Credit Agreement as amended hereby have
          been obtained and are in full force and effect and that a true,
          correct and complete copy of each such consent, authorization,
          approval and filing is attached thereto;
<PAGE>

                                                                               4

               (D)  favorable opinions of counsel for the Borrowers as to such
          matters as the Administrative Agent may reasonably request; and

               (E)  such other approvals, opinions and documents as any Lender,
          through the Administrative Agent, may reasonably request.

     SECTION 4.  Representations and Warranties. Each Borrower represents and
warrants that (a) the representations and warranties contained in Article III of
the Credit Agreement (with each reference therein to "this Agreement",
"hereunder" and words of like import referring to the Credit Agreement being
deemed to be a reference to this Amendment and the Credit Agreement as amended
hereby) are true and correct on and as of the Amendment Date as though made on
and as of such date, and (b) no event has occurred and is continuing, or would
result from the execution and delivery of this Amendment, that constitutes a
Default or an Event of Default.

     SECTION 5.  Effect on the Credit Agreement. Except as specifically provided
above, the Credit Agreement shall continue to be in full force and effect and is
hereby in all respects ratified and confirmed. The execution, delivery and
effectiveness of this Amendment shall not, except as expressly provided herein,
operate as a waiver of any right, power or remedy of the Lenders, the Agents or
the Fronting Bank under the Credit Agreement, nor constitute a waiver of any
provision of the Credit Agreement.

     SECTION 6.  Costs, Expenses and Taxes. The Borrowers agree jointly and
severally to pay on demand all costs and expenses of the Administrative Agent in
connection with the preparation, execution and delivery of this Amendment and
the other instruments and documents to be delivered hereunder, including,
without limitation, the reasonable fees and out-of-pocket expenses of counsel
for the Administrative Agent with respect thereto, and all costs and expenses
(including, without limitation, counsel fees and expenses), if any, in
connection with the enforcement (whether through negotiations, legal proceedings
or otherwise) of this Amendment or such other instruments and documents. In
addition, the Borrowers agree jointly and severally to pay any and all stamp and
other taxes payable or determined to be payable in connection with the execution
and delivery of this Amendment and the other instruments and documents to be
delivered hereunder, and agree jointly and severally to save the Agents, the
Fronting Bank and the Lenders harmless from and against any and all liabilities
with respect to or resulting from any delay in paying or omission to pay such
taxes.
<PAGE>

                                                                               5

     SECTION 7.  Execution in Counterparts. This Amendment may be executed in
any number of counterparts and by different parties hereto in separate
counterparts, each of which when so executed and delivered shall be deemed to be
an original and all of which taken together shall constitute but one and the
same instrument.

     SECTION 8.  Governing Law. This Amendment shall be governed by, and
construed in accordance with, the internal laws of the State of the New York.

                        [Signature pages to follow.]
<PAGE>

                                                                             S-1

                         TXU CORP.



                         By     /s/ Kirk R. Oliver
                           ---------------------------------
                         Name:  Kirk R. Oliver
                         Title: Treasurer and Assistant Secretary

                         TXU ELECTRIC COMPANY


                         By     /s/ Laura Conn
                           ---------------------------------
                         Name:  Laura Conn
                         Title: Treasurer and Assistant Secretary

                         TXU GAS COMPANY


                         By     /s/ Laura Conn
                           ---------------------------------
                         Name:  Laura Conn
                         Title: Treasurer and  Assistant Secretary
<PAGE>

                                                                             S-2

                         THE CHASE MANHATTAN BANK,
                         individually and as Administrative Agent, Competitive
                         Advance Facility Agent and Fronting Bank


                         By     /s/ Robert W. Traband
                           ---------------------------------
                         Name:  Robert W. Traband
                         Title: Vice President
<PAGE>

                                                                             S-3

                         ABN AMRO BANK N.V.


                         By     /s/ Kevin S. McFadden
                           ---------------------------------
                         Name:  Kevin S. McFadden
                         Title: Group Vice President



                         By     /s/ Jeffrey Dodd
                           ---------------------------------
                         Name:  Jeffrey Dodd
                         Title: Group Vice President
<PAGE>

                                                                             S-4

                         THE BANK OF TOKYO-MITSUBISHI, LTD.


                         By     /s/ John M. Mearns
                           ---------------------------------
                         Name:  John M. Mearns
                         Title: Vice President and Manager
<PAGE>

                                                                             S-5

                         BNP PARIBAS


                         By     /s/ Mark A. Renaus
                           ---------------------------------
                         Name:  Mark A. Renaud
                         Title: Director


                         By     /s/ Andrew S. Platt
                           ---------------------------------
                         Name:  Andrew S. Platt
                         Title: Vice President
<PAGE>

                                                                             S-6


                         [This page intentionally left blank]
<PAGE>

                                                                             S-7

                         BAYERISCHE LANDESBANK GIROZENTRALE,
                         CAYMAN ISLANDS BRANCH


                         By     /s/ Peter Obermann
                           ---------------------------------
                         Name:  Peter Obermann
                         Title: Senior Vice President



                         By     /s/ Sean O'Sullivan
                           ---------------------------------
                         Name:  Sean O'Sullivan
                         Title: Vice President
<PAGE>

                                                                             S-8


                         [This page intentionally left blank]
<PAGE>

                                                                             S-9

                         CITIBANK, NA


                         By     /s/ Sandip Sen
                           ---------------------------------
                         Name:  Sandip Sen
                         Title: Managing Director and Vice President
<PAGE>

                                                                            S-10

                         COMMERZBANK AG, NEW YORK AND GRAND CAYMAN BRANCHES


                         By     /s/ W. David Suttles
                           ---------------------------------
                         Name:  W. David Suttles
                         Title: Vice President



                         By     /s/ Subash R. Viswanathan
                           ---------------------------------
                         Name:  Subash R. Viswanathan
                         Title: Senior Vice President
<PAGE>

                                                                            S-11

                         CREDIT LYONNAIS NEW YORK BRANCH


                         By     /s/ Phillippe Soustra
                           ---------------------------------
                         Name:  Phillippe Soustra
                         Title: Senior Vice President
<PAGE>

                                                                            S-12

                         CREDIT SUISSE FIRST BOSTON


                         By     /s/ Jay Chall
                           ---------------------------------
                         Name:  Jay Chall
                         Title: Director



                         By     /s/ Lalita Advani
                           ---------------------------------
                         Name:  Lalita Advani
                         Title: Assistant Vice President
<PAGE>

                                                                            S-13

                         THE DAI-ICHI KANGYO BANK, LTD.


                         By     /s/ Andreas Pantelli
                           ---------------------------------
                         Name:  Andreas Pantelli
                         Title: Senior Vice President
<PAGE>

                                                                            S-14

                         DANSKE BANK A/S


                         By     /s/ Dennis T. Shugrue
                           ---------------------------------
                         Name:  Dennis T. Shugrue
                         Title: Assistant Vice President

                         By     /s/ John A. O'Neill
                           ---------------------------------
                         Name:  John A. O'Neill
                         Title: Vice President
<PAGE>

                                                                            S-15


                         DEUTSCHE BANK AG, NEW YORK AND/OR CAYMAN ISLANDS
                         BRANCHES


                         By     /s/ Joel Makowsky
                           ---------------------------------
                         Name:  Joel Makowsky
                         Title: Vice President



                         By     /s/ Hans C. Narberhau
                           ---------------------------------
                         Name:  Hans C. Narberhau
                         Title: Vice President
<PAGE>

                                                                            S-16

                         [This page intentionally left blank]
<PAGE>

                                                                            S-17

                         FIRST UNION NATIONAL BANK


                         By     /s/ Joe K. Dancy
                           ---------------------------------
                         Name:  Joe K. Dancy
                         Title: Vice President
<PAGE>

                                                                            S-18

                         GUARANTY FEDERAL BANK, FSB


                         By     /s/ Jim R. Hamilton
                           ---------------------------------
                         Name:  Jim R. Hamilton
                         Title: Vice President
<PAGE>

                                                                            S-19

                         THE INDUSTRIAL BANK OF JAPAN, LIMITED
                         NEW YORK BRANCH


                         By     /s/ Michael N. Oakes
                           ---------------------------------
                         Name:  Michael N. Oakes
                         Title: Senior Vice President, Houston Office
<PAGE>

                                                                            S-20

                         KBC BANK N.V.


                         By     /s/ Jean-Pierre Diels/Patrick A. Janssens
                           ----------------------------------------------
                         Name:  Jean-Pierre Diels/Patrick A. Janssens
                         Title: First Vice President and Vice President
<PAGE>

                                                                            S-21

                         LEHMAN COMMERCIAL PAPER INC.


                         By     /s/ G. Andrew Keith
                           ---------------------------------
                         Name:  G. Andrew Keith
                         Title: Authorized Signatory
<PAGE>

                                                                            S-22

                         LLOYDS TSB BANK PLC


                         By     /s/ Windsor R. Davies
                           ---------------------------------
                         Name:  Windsor R. Davies
                         Title: Director, Corporate Banking, USA



                         By     /s/ David Rodway
                           ---------------------------------
                         Name:  David Rodway
                         Title: Assistant Director
<PAGE>

                                                                            S-23

                         MELLON BANK, N.A.


                         By     /s/ Roger E. Howard
                           ---------------------------------
                         Name:  Roger E. Howard
                         Title: Vice President
<PAGE>

                                                                            S-24

                         [This page intentionally left blank]
<PAGE>

                                                                            S-25

                         NATIONAL AUSTRALIA BANK LIMITED
                         A.C.N. 004044937


                         By     /s/ Frank J. Campiglia
                           ---------------------------------
                         Name:  Frank J. Campiglia
                         Title: Vice President
<PAGE>

                                                                            S-26

                         THE ROYAL BANK OF SCOTLAND PLC


                         By     /s/ Clark McGrin
                           ---------------------------------
                         Name:  Clark McGrin
                         Title: Senior Vice President
<PAGE>

                                                                            S-27

                         [This page intentionally left blank]
<PAGE>

                                                                            S-28

                         SOCIETE GENERALE


                         By     /s/ David Bird
                           ---------------------------------
                         Name:  David Bird
                         Title: Vice President
<PAGE>

                                                                            S-29

                         [This page intentionally left blank]
<PAGE>

                                                                            S-30

                         THE SUMITOMO BANK LIMITED


                         By     /s/ C. Michael Garrido
                           ---------------------------------
                         Name:  C. Michael Garrido
                         Title: Senior Vice President
<PAGE>

                                                                            S-31

                         TORONTO DOMINION (TEXAS), INC.


                         By     /s/ Mark A. Baird
                           ---------------------------------
                         Name:  Mark A. Baird
                         Title: Vice President
<PAGE>

                                                                            S-32

                         WESTDEUTSCHE LANDESBANK GIROZENTRALE,
                         NEW YORK BRANCH


                         By     /s/ Duncan M. Robertson
                           ---------------------------------
                         Name:  Duncan M. Robertson
                         Title: Director



                         By     /s/ Anthony Alessandro
                           ---------------------------------
                         Name:  Anthony Alessandro
                         Title: Manager
<PAGE>

                                                                            S-33

                         THE BANK OF NEW YORK


                         By     /s/ Nathan S. Howard
                           ---------------------------------
                         Name:  Nathan S. Howard
                         Title: Vice President
<PAGE>

                                                                            S-34

                         FLEET NATIONAL BANK


                         By     /s/ Robert Lanigan
                           ---------------------------------
                         Name:  Robert Lanugan
                         Title: Managing Director
<PAGE>

                                                                            S-35

                         BANCA NAZIONALE DEL LAVORO  S.p.A.
                         NEW YORK BRANCH


                         By     /s/ Carlo Vecchi
                           ---------------------------------
                         Name:  Carlo Vecchi
                         Title: Senior Vice President



                         By     /s/ Robert Mancone
                           ---------------------------------
                         Name:  Robert Mancone
                         Title: Vice President
<PAGE>

                                                                            S-36

                         THE CHASE MANHATTAN BANK


                         By     /s/ Robert W. Traband
                           ---------------------------------
                         Name:  Robert W. Traband
                         Title: Vice President
<PAGE>

                                                                            S-37

                         UBS AG, STAMFORD BRANCH

                         By     /s/ Dorothy L. McKinley
                           ---------------------------------
                         Name:  Dorothy L. McKinley
                         Title: Director


                         By     /s/ Lynne B. Alfarone
                           ---------------------------------
                         Name:  Lynne B. Alfarone
                         Title: Associate Director
<PAGE>

                                                                            S-38

                         BANK OF AMERICA, N.A.


                         By     /s/ Michelle A. Schoenfeld
                           ---------------------------------
                         Name:  Michelle A. Schoenfeld
                         Title: Vice President
<PAGE>

                                                                            S-39

                         THE FUJI BANK, LIMITED


                         By     /s/ Shinichiro Kuruma
                           ---------------------------------
                         Name:  Shinichiro Kuruma
                         Title: Vice President & Manager
<PAGE>

                                                                            S-40

                         BANK ONE, NA


                         By     /s/ Sean Drinan
                           ---------------------------------
                         Name:  Sean Drinan
                         Title: Director