<PAGE>   1
                                                                   EXHIBIT 10.28

                        HOUSTON INDUSTRIES INCORPORATED
                            SAVINGS RESTORATION PLAN

                                   ARTICLE I

                           ESTABLISHMENT AND PURPOSE

        1.1     Establishment. Houston Industries Incorporated, a Texas
corporation (the "Company"), hereby establishes the Houston Industries
Incorporated Savings Restoration Plan (the "Plan"), effective January 1, 1991.

        1.2     Purpose. The purpose of this Plan generally is to provide the
amount of the Employer Matching Contribution which would otherwise be paid under
the Savings Plan of Houston Industries Incorporated but which is not paid under
that Plan on account of Section 401(a)(17) of the Internal Revenue Code of 1986,
as amended (the "Code"), which limits to $200,000 (indexed annually) the annual
compensation of each Participant which may be taken into account under the
Savings Plan for any Plan Year. Since Participant contributions to the Savings
Plan are limited, the Employer Matching Contribution is also foregone.

        1.3     Application of Plan. The terms of this Plan are applicable only
to full-time, salaried officers or other highly-compensated employees of the
Company or any of its adopting Affiliates from and after January 1, 1991 if the
limitations of Code Section 401(a)(17) affect such individual.

                                   ARTICLE II

                          DEFINITIONS AND CONSTRUCTION

        2.1     Definitions. Except as otherwise indicated, the terms used in
this Plan shall have the same meaning as they have under the Savings Plan of
Houston




<PAGE>   2
Industries Incorporated, as amended and restated effective January 1, 1989 and
as thereafter amended and in effect on the applicable date (the "Savings Plan").

     2.2  Gender and Number. Except when otherwise indicated by the context,
any masculine terminology used in the Plan shall also include the feminine
gender, and the definition of any term in the singular shall also include the
plural.

     2.3  Severability. In the event any provision of the Plan shall be held
invalid or illegal for any reason, any illegality or invalidity shall not
affect the remaining parts of the Plan, but the Plan shall be construed and
enforced as if the illegal or invalid provision had never been inserted, and
the Company shall have the privilege and opportunity to correct and remedy such
questions of illegality or invalidity by amendment as provided in the Plan.

     2.4  Applicable Law. This Plan shall be governed and construed in
accordance with the laws of the State of Texas.

     2.5  Plan Not an Employee Contract. This Plan is not an employment
contract. It does not give to any person the right to be continued in
employment, and all employees remain subject to change of salary, transfer,
change of job, discipline, layoff, discharge, or any other change of employment
status.

                                  ARTICLE III

                                 Participation

     3.1  Participants. A person who is a full-time, salaried officer or
highly-compensated employee of the Company or any of its adopting Affiliates
shall become a Participant in this Plan when the employer matching contributions
made by the


Houston Industries Incorporated
Savings Restoration Plan
Page 2

<PAGE>   3
Company under the Savings Plan are limited on account of the limitations on
Participant contributions by Code Section 401(a)(17).

                                   ARTICLE IV

                                    BENEFITS

        4.1     Amount of Benefits. The amount payable to or in respect of a
Participant hereunder shall be equal to the difference between (i) the
aggregate amount of Employer Matching Contributions which would have been
allocated in respect of the Participant under the Savings Plan if the
Participant had made the maximum Basic Contribution to the Savings Plan without
regard to the limitation of Code Section 401(a)(17) and (ii) the aggregate
amount of Employer Matching Contributions actually allocated in respect of the
Participant. The amount so credited shall earn interest at the same rate and be
credited in the same manner as Fund A under the Savings Plan.

        4.2     Form of Payment and Commencement Date.

                (a)     Form of Payment. Benefits payable under this Plan shall
be paid in the same manner as distributions payable under the Savings Plan.
However, the Personnel Committee may direct the payment of such benefits due a
Participant, spouse, or beneficiary under this Plan in the form of an
actuarially equivalent lump-sum payment. The actuarial assumptions for
computing the lump-sum payment shall be determined by the Personnel Committee.

                (b)     Commencement Date. Benefits payable under this Plan
shall commence on or about the same date that distributions are made under the
Savings Plan.

        4.3     Vesting. A Participant shall become vested in the benefit
payable under Section 4.1 above at the same time that he becomes vested under
the Savings Plan.


HOUSTON INDUSTRIES INCORPORATED
SAVINGS RESTORATION PLAN
PAGE 3
<PAGE>   4
                                   ARTICLE V

                                 ADMINISTRATION


However, a Participant (and his beneficiary) shall have no right to a benefit
under this Plan if the Personnel Committee determines that the Participant
engaged in a willful, deliberate, or gross act of commission or omission which
is injurious to the finances or reputation of the Company or any of its
Affiliates.

     4.4 Funding. All amounts paid under this Plan shall be paid in cash from
the general assets of the Company. Benefits shall be reflected on the accounting
records of the Company but shall not be construed to create, or require the
creation of, a trust, custodial, or escrow account. No employee shall have any
right, title, or interest whatever in or to any investment reserves, accounts,
or funds that the Company may purchase, establish, or accumulate to aid in
providing the benefits described in this Plan. Nothing contained in this Plan,
and no action taken pursuant to its provisions, shall create or be construed to
create a trust or a fiduciary relationship of any kind between the Company and
an employee or any other person. Neither an employee nor a beneficiary of an
employee shall acquire any interest greater than that of an unsecured creditor.

     4.5 Tax Withholding. The Company may withhold from a payment any federal,
state, or local taxes required by law to be withheld with respect to such
payment and such sums as the Company may reasonably estimate as necessary to
cover any taxes for which the Company may be liable and which may be assessed
with regard to such payment.

     4.6 Effect on Other Plans. Amounts accrued or paid under this Plan shall
not be considered compensation for the purpose of the Company's retirement,
savings, life insurance or disability plans.

     4.7 Non-Transferability. A Participant or his beneficiary shall have no
rights by way of anticipation or otherwise to assign or otherwise dispose of any
interest under this Plan, nor shall rights be assigned or transferred by
operation of law.


HOUSTON INDUSTRIES INCORPORATED
SAVINGS RESTORATION PLAN
PAGE 4
<PAGE>   5
                                   ARTICLE V

                                 Administration

     5.1 Administration. The Plan shall be administered, construed and
interpreted by the Personnel Committee of the Board of Directors of the Company
(the "Personnel Committee").

     5.2 Finality of Determination. The determination of the Personnel Committee
as to any disputed questions arising under this Plan, including questions of
construction and interpretation, shall be final, binding, and conclusive upon
all persons.

     5.3 Expenses. The expenses of administering the Plan shall be borne by the
Company.

     5.4 Indemnification and Exculpation. The members of the Personnel
Committee, its agents, and officers, directors, and employees of the Company and
its Affiliates shall be indemnified and held harmless by the Company against and
from any and all loss, cost, liability, or expense that may be imposed upon or
reasonably incurred by them in connection with or resulting from any claim,
action, suit, or proceeding to which they may be a party or in which they may be
involved by reason of any action taken or failure to act under this Plan and
against and from any and all amounts paid by them in settlement (with the
Company's written approval) or paid by them in satisfaction of a judgment in any
action, suit or proceeding. The foregoing provision shall not be applicable to
any person if the loss, cost, liability, or expense is due to such person's
gross negligence or willful misconduct.





HOUSTON INDUSTRIES INCORPORATED
SAVINGS RESTORATION PLAN
PAGE 5


<PAGE>   6

                                   ARTICLE VI

                       Merger, Amendment and Termination

     6.1 Merger, Consolidation, or Acquisition. In the event of a merger,
consolidation, or acquisition where the Company is not the surviving
corporation, unless the successor or acquiring corporation shall elect to
continue and carry on the Plan, this Plan shall terminate with respect to the
Company, and no additional benefits shall accrue for the employees of the
Company. Unpaid benefits shall continue to be paid as scheduled unless the
successor or acquiring corporation elects to accelerate payment.

     6.2 Amendment and Termination. The Board of Directors of the Company may
amend, modify, or terminate the Plan at any time. In the event of a termination
of the Plan pursuant to this Section, unpaid benefits shall continue to be an
obligation of the Company and shall be paid as scheduled.

     IN WITNESS WHEREOF, the Company has caused this instrument to be executed
by its duly authorized officers on this 20th day of February, 1991, effective
as of the 1st day of January 1991.



                                             HOUSTON INDUSTRIES INCORPORATED


                                             By /s/ [SIGNATURE ILLEGIBLE]
                                             ---------------------------------

ATTEST:


/s/ [SIGNATURE ILLEGIBLE]
------------------------------------
[SEAL] Assistant Corporate Secretary


HOUSTON INDUSTRIES INCORPORATED
SAVINGS RESTORATION PLAN
PAGE 6

<PAGE>   7
     The foregoing Houston Industries Incorporated Savings Restoration Plan, as
established effective January 1, 1991, is hereby adopted this _______ day of
____________________, 1991


                                             HOUSTON LIGHTING & POWER COMPANY



                                             By
                                                 ------------------------------

ATTEST:



-------------------------------
[SEAL]

                                             UTILITY FUELS, INC.



                                             By
                                                 ------------------------------

ATTEST:



-------------------------------
[SEAL]












HOUSTON INDUSTRIES INCORPORATED
SAVINGS RESTORATION PLAN
PAGE 7


<PAGE>   8
                        HOUSTON INDUSTRIES INCORPORATED
                            SAVINGS RESTORATION PLAN

                          (Effective January 1, 1991)

                                First Amendment

     Houston Industries Incorporated, a Texas corporation (the "Company"),
having established the Houston Industries Incorporated Savings Restoration
Plan, effective January 1, 1991 (the "Plan"), and having reserved the right to
amend the Plan under Section 6.2 thereof, does hereby amend Section 3.1 of the
Plan, effective January 1, 1992, to read as follows:

          "A person who is a full-time, salaried officer or highly
          compensated employee of the Company or any of its adopting
          Affiliates shall participate in this Plan for each Plan Year
          (i) in which the Participant makes the maximum Pre-Tax and/or
          After-Tax Basic Contribution permitted under the Savings
          Plan and (ii) during which the Employer Matching Contributions
          made by the Employer under the Savings Plan are limited on
          account of the limitations on Participant compensation under
          Code Section 401(a)(17)."

     IN WITNESS WHEREOF, Houston Industries Incorporated has caused these
presents to be executed by its duly authorized officers and to be affixed with
its corporate seal, in a number of copies, all of which shall constitute but
one and the same instrument which may be sufficiently evidenced by any executed
copy hereof, this 1st day of October, 1991, but effective January 1, 1992.

                                             HOUSTON INDUSTRIES INCORPORATED

                                             By  /s/ [SIGNATURE ILLEGIBLE]
                                               --------------------------------
                                                Vice President

ATTEST:

/s/ [SIGNATURE ILLEGIBLE]
------------------------------
Assistant Corporate Secretary

[SEAL]
<PAGE>   9

     RECEIPT OF A COPY OF THE FOREGOING FIRST AMENDMENT TO THE HOUSTON
INDUSTRIES INCORPORATED SAVINGS RESTORATION PLAN IS HEREBY ACKNOWLEDGED, THIS
_____ DAY OF _______________, 19__.

                                        HOUSTON LIGHTING & POWER COMPANY

                                        By  /s/ [SIGNATURE ILLEGIBLE]
                                          -------------------------------------
                                            President

ATTEST:

/s/ [SIGNATURE ILLEGIBLE]
----------------------------------
Assistant Corporate Secretary

[SEAL]

                                        UTILITY FUELS, INC.

                                        By  /s/ [SIGNATURE ILLEGIBLE]
                                          -------------------------------------
                                            President

ATTEST:

/s/ [SIGNATURE ILLEGIBLE]
----------------------------------
Secretary

[SEAL]

<PAGE>   10
                         HOUSTON INDUSTRIES INCORPORATED
                            SAVINGS RESTORATION PLAN

                           (Effective January 1, 1991)


                                Second Amendment


               Houston Industries Incorporated, a Texas corporation (the
"Company"), having established the Houston Industries Incorporated Savings
Restoration Plan, effective January 1, 1991, and as thereafter amended (the
"Plan"), and having reserved the right to amend the Plan under Section 6.2
thereof, does hereby amend the Plan, effective as of the dates specified therein
as follows:

               1. Section 1.3 of the Plan is hereby amended, effective August 6,
1997, by inserting the following sentence at the end thereof:

        "For purposes of this Plan, the term "Company" shall include Houston
        Industries Incorporated, any successor thereto, and/or any Affiliate
        adopting this Plan with approval of the Board of Directors."

               2. A new Section 6.3 is hereby added to Article XI of the Plan,
effective October 1, 1997, to read as follows:

               "6.3 OPCO as Successor Employer. Effective on or about October 1,
        1997, STP Nuclear Operating Company, a Texas nonprofit corporation
        ("OPCO" herein), assumed the responsibilities of Houston Lighting &
        Power Company ("HL&P" herein), a division of the Company, as project
        manager of the South Texas Project. In connection therewith, OPCO
        employed substantially all of the former employees of HL&P stationed at
        the South Texas Project who have been engaged in the operation and
        management of the South Texas Project as employees of HL&P ("OPCO
        Employees"). Section 8.6.4 of that certain South Texas Project
        Transition Agreement between the Company and the remaining owners of the
        South Texas Project, dated effective November 17, 1997, provides that
        OPCO shall assume any and all liabilities for providing benefits under
        this Plan to the former HL&P employees who became OPCO Employees. In
        furtherance thereof, the liabilities for

<PAGE>   11

        benefits accrued under this Plan as of September 30, 1997 with respect
        to OPCO Employees have been transferred from the books and records of
        the Company to the books and records of OPCO. Accordingly, from and
        after October 1, 1997, the Company shall have no further obligation with
        respect to such benefits, if any, accrued under this Plan on behalf of
        OPCO Employees and the OPCO Employees shall look solely to the OPCO Plan
        and OPCO for the payment of such benefits."

               IN WITNESS WHEREOF, Houston Industries Incorporated has caused
these presents to be executed by its duly authorized officers in a number of
copies, all of which shall constitute one and the same instrument, which may be
sufficiently evidenced by any executed copy hereof, this 26th day of February,
1998, but effective as of the dates specified herein.

                                        HOUSTON INDUSTRIES INCORPORATED



                                        By /s/ LEE W. HOGAN
                                          --------------------------------------
                                             Name: Lee W. Hogan
                                             Title: Executive Vice President

ATTEST:

/s/ [Signature Illegible]
-----------------------------------
Assistant Corporate Secretary