<PAGE>   1
                                                                 EXHIBIT 4(d)(1)
                                                                  EXECUTION COPY



                 AMENDMENT, dated as of December 23, 1997 (this "Amendment"),
to the Credit Agreement dated as of August 6, 1997 (as the same may be amended,
supplemented or otherwise modified from time to time, the "Credit Agreement"),
among: (i) HOUSTON INDUSTRIES FINANCECO LP, a Delaware limited partnership (the
"Borrower"); (ii) HOUSTON INDUSTRIES INCORPORATED, a Texas corporation; (iii)
the several banks and other financial institutions from time to time parties
thereto (collectively, the "Banks," and each individually, a "Bank"); (iv)
CHASE SECURITIES INC., as Arranger (in such capacity, the "Arranger"); and (v)
THE CHASE MANHATTAN BANK, as Administrative Agent (in such capacity, the
"Agent").


                             W I T N E S S E T H :

                 WHEREAS, pursuant to the Credit Agreement, the Banks have
agreed to make certain loans and other extensions of credit to the Borrower;
and

                 WHEREAS, the Borrower has requested, and, upon this Amendment
becoming effective, the Majority Banks have agreed, that certain provisions of
the Credit Agreement be amended in the manner provided for in this Amendment;

                 NOW, THEREFORE, the parties hereto hereby agree as follows:

                 SECTION 1.  DEFINITIONS.

                 1.1      Defined Terms.  Unless otherwise defined herein and
except as set forth in this Amendment, terms defined in the Credit Agreement
are used herein as therein defined.

                 SECTION 2.  AMENDMENTS TO CREDIT AGREEMENT.

                 2.1      Amendment to Section 1.1 of the Credit Agreement.
Section 1.1 of the Credit Agreement is hereby amended by adding thereto the
following definition in its appropriate alphabetical order:

                 "Project Finance Entity" means any entity established or used
         primarily to acquire and/or hold assets (the "Project Finance Assets")
         so long as HII or a Subsidiary of HII (i) owns at least a portion of
         the outstanding shares of Capital Stock or other ownership interests
         having ordinary voting power to elect directors or other managers of
         such entity and (ii) has or will have a role in managing such Project
         Finance Assets.




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                 2.2      Amendment to Section 8.4(g)(v) of the Credit
Agreement.  Section 8.4(g)(v) of the Credit Agreement is hereby amended by
deleting said Section in its entirety and substituting in lieu thereof the
following:

         "at any time (x) at which no Default or Event of Default has occurred
         and is continuing, (y) that Projected Available Cash exceeds Projected
         Borrower Debt Service for the fiscal quarter of HII then in effect and
         (z) that the long-term senior secured debt rating then in effect for
         HII is at least BBB by S&P or Baa2 by Moody's, HII may make HII
         Investments in any domestic Subsidiary of HII or any Project Finance
         Entity so long as such Subsidiary or Project Finance Entity (i) is a
         Subsidiary or Project Finance Entity domiciled and organized in the
         United States, having all or substantially all of its assets and
         operations located in the United States and (ii) is (A) directly or
         indirectly engaged in one or more businesses which are primarily
         related to the normal conduct of the domestic utility business of HL&P
         or NorAm in accordance with normal industry standards as generally in
         effect at such time or (B) formed for the purpose of providing or
         obtaining financing for a Subsidiary or a Project Finance Entity of
         the type described in clause (A); provided that the requirement of
         clause (y) would be satisfied after giving effect to (1) such HII
         Investment and (2) any sources of cash available or reasonably
         expected by HII at the time of the proposed investment to be available
         during the fiscal quarter of HII then in effect; and"

                 SECTION 3. MISCELLANEOUS.

                 3.1      Effectiveness.  This Amendment shall become effective
on the date upon which the Agent shall have received counterparts of this
Amendment, duly executed and delivered by the Borrower, HII, the Agent and the
Majority Banks.

                 3.2      Representations and Warranties.  After giving effect
to the amendments contained herein, each of the Borrower and HII hereby
confirm, reaffirm and restate the representations and warranties set forth in
Article VII of the Credit Agreement; provided that each reference in such
Article VII to "this Agreement" shall be deemed to be a reference both to this
Amendment and to the Credit Agreement as amended by this Amendment.

                 3.3      Payment of Expenses.  The Borrower agrees to pay or
reimburse the Agent for all of its out-of- pocket costs and reasonable expenses
incurred in connection with this Amendment, any other documents prepared in
connection herewith and the transactions contemplated hereby, including,
without limitation, the reasonable fees and disbursements of counsel to the
Agent.

                 3.4      Continuing Effect; No Other Amendments.  Except as
expressly amended hereby, all of the terms and provisions of the Credit
Agreement and the other Loan Documents are and shall remain in full force and
effect.  The amendments contained herein shall not constitute an amendment or
waiver of any other provision of the Credit Agreement or the other Loan
Documents or for any purpose except as expressly set forth herein.





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                 3.5      Counterparts.  This Amendment may be executed in any
number of counterparts by the parties hereto, each of which counterparts when
so executed shall be an original, but all the counterparts shall together
constitute one and the same instrument.

                 3.6      GOVERNING LAW.  THIS AMENDMENT SHALL BE GOVERNED
BY, AND CONSTRUED AND INTERPRETED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF
NEW YORK.





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                 IN WITNESS WHEREOF, the parties hereto have caused this
Amendment to be executed and delivered by their respective duly authorized
officers as of the date first above written.

                                  HOUSTON INDUSTRIES
                                  FINANCECO LP
                                  
                                  By:  HOUSTON INDUSTRIES
                                       FINANCECO GP, LLC,
                                       its General Partner
                                  
                                  
                                  By:/s/M. Keller C.                      
                                     -------------------------------------------
                                     Title: Treasurer
                                  
                                  
                                  HOUSTON INDUSTRIES
                                  INCORPORATED
                                  
                                  
                                  
                                  By:/s/Stephen W. Naeve                  
                                     -------------------------------------------
                                     Title:  Executive Vice President and Chief
                                                Financial Officer
                                  
                                  
                                  THE CHASE MANHATTAN BANK, as
                                  Agent and as a Bank
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  BANKBOSTON, N.A.
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:





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                                  BANK OF MONTREAL
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  THE BANK OF NEW YORK
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  THE BANK OF NOVA SCOTIA
                                  
                                  
                                  
                                  By:/s/ F.C.H. Ashby                          
                                     -------------------------------------------
                                     F.C.H. Ashby
                                     Title: Senior Manager Loan Operations
                                  
                                  
                                  THE BANK OF TOKYO-MITSUBISHI,
                                  LTD., HOUSTON AGENCY
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  BARCLAYS BANK PLC
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:





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                                  CAISSE NATIONALE DE CREDIT
                                  AGRICOLE
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  CIBC INC.
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  CITIBANK, N.A.
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  COMERICA BANK
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:





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                                  COMMERZBANK
                                  AKTIENGESELLSCHAFT,
                                  ATLANTA AGENCY
                                  
                                  
                                  
                                  By:/s/D. Suttles                             
                                     -------------------------------------------
                                     Title: Vice President
                                  
                                  
                                  
                                  By:/s/P. Mahoney                             
                                     -------------------------------------------
                                     Title: Assistant Treasurer
                                  
                                  
                                  CREDIT LYONNAIS
                                  NEW YORK BRANCH
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  CREDIT SUISSE FIRST BOSTON
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  THE DAI-ICHI KANGYO BANK,
                                  LIMITED
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:





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                                  FIRST UNION NATIONAL BANK
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  FLEET NATIONAL BANK
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  THE FUJI BANK, LIMITED -
                                  HOUSTON AGENCY
                                  
                                  
                                  
                                  By:/s/David Kelley                           
                                     -------------------------------------------
                                     Title: Senior Vice President
                                  
                                  
                                  THE INDUSTRIAL BANK OF JAPAN,
                                  LIMITED, NEW YORK BRANCH
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  THE LONG-TERM CREDIT BANK OF
                                  JAPAN, LTD.
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:





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                                  MELLON BANK, N.A.
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  MORGAN GUARANTY TRUST
                                  COMPANY OF NEW YORK
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  NATIONSBANK OF TEXAS, N.A.
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  THE NORTHERN TRUST COMPANY
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  ROYAL BANK OF CANADA
                                  
                                  
                                  
                                  By:/s/Tom J. Oberaigner                      
                                     -------------------------------------------
                                     Tom J. Oberaigner
                                     Title: Manager





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                                  THE SAKURA BANK, LIMITED
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  SOCIETE GENERALE,
                                  SOUTHWEST AGENCY
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  THE SUMITOMO BANK, LIMITED
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  THE TOKAI BANK, LTD.
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  TORONTO DOMINION (TEXAS), INC.
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:





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                                  UNION BANK OF SWITZERLAND,
                                  NEW YORK BRANCH
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  WACHOVIA BANK OF GEORGIA, N.A.
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  WESTDEUTSCHE LANDESBANK
                                  GIROZENTRALE, NEW YORK
                                  
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  By:                                          
                                     -------------------------------------------
                                     Title:
                                  
                                  
                                  THE YASUDA TRUST AND BANKING
                                  COMPANY LIMITED
                                  NEW YORK BRANCH
                                  
                                  
                                  
                                  By:/s/R.M. Laudenschlager                    
                                     -------------------------------------------
                                     Rohn Laudenschlager
                                     Title: Senior Vice President





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