<PAGE>


                                                                   Exhibit 10.15


                               FIRST AMENDMENT TO
                           EMPLOYEE MATTERS AGREEMENT
                                     BETWEEN
                          RELIANT ENERGY, INCORPORATED
                                       AND
                             RELIANT RESOURCES, INC.


                  WHEREAS, in connection with the separation of Reliant
Resources, Inc., a Delaware corporation ("Resources"), from Reliant Energy,
Inc., a Texas corporation ("REI"), REI and Resources entered into that certain
Employee Matters Agreement Between Reliant Energy, Incorporated and Reliant
Resources, Inc., dated December 31, 2000 (the "Agreement"), to allocate between
them assets, liabilities and responsibilities with respect to certain employee
compensation, benefit plans and programs, and certain employment matters related
to the separation; and

                  WHEREAS, pursuant to the distribution by REI of all shares it
held of Resources common stock to its shareholders on September 30, 2002,
effective as of September 30, 2002, REI and Resources became separate,
non-affiliated companies; and further

                  WHEREAS, as a result of the restructuring of REI, CenterPoint
Energy, Inc., a Texas corporation ("CNP"), has succeeded to the rights and
obligations of REI under the Agreement, effective as of August 31, 2002; and
further

                  WHEREAS, due to the separation of Resources from REI occurring
later than anticipated as of the execution of the Agreement, CNP and Resources
desire to amend the Agreement to (1) reflect previously agreed changes in
certain provisions of the Agreement and (2) clarify certain other provisions of
the Agreement;

                  NOW, THEREFORE, in consideration of the foregoing, the parties
hereto agree to the amendment of the Agreement, effective as of December 31,
2000, unless otherwise provided, as follows:



                                       1
<PAGE>


                  1. The definition of "Deferred Compensation Plan" in Section
1.11 of the Agreement is hereby amended to include the Reliant Resources, Inc.
Deferral Plan.

                  2. The definition of "LTIP" in Section 1.37 of the Agreement
is hereby amended to include the Reliant Resources, Inc. 2002 Stock Plan and
Reliant Resources, Inc. 2002 Long-Term Incentive Plan.

                  3. For purposes of the Agreement, all references to "REI"
shall mean Reliant Energy, Incorporated, a Texas corporation, prior to August
31, 2002, and CenterPoint Energy, Inc., a Texas corporation, from and after
August 31, 2002, and, accordingly, the first sentence in the definition of "REI"
in Section 1.49 of the Agreement is hereby amended to read as follows:

         "'REI' means (i) Reliant Energy, Incorporated, a Texas corporation,
         prior to August 31, 2002; and (ii) CenterPoint Energy, Inc., a Texas
         corporation, from and after August 31, 2002."

                  4. The definition of "REI Stock Value" in Section 1.52 of the
Agreement is hereby amended to read as follows:

                  "1.52 REI STOCK VALUE. 'REI Stock Value' means the closing
         sales price of a share of REI Common Stock (with dividend) on the New
         York Stock Exchange - Composite Transactions reporting system on the
         Record Date."

                  5. The provisions of the Agreement shall not apply to Orion
Power Holdings, Inc., and its subsidiaries, acquired by Resources on February
19, 2002, and, accordingly, the definition of "Resources Group" in Section 1.57
of the Agreement is hereby amended to read as follows:

                  "1.57 RESOURCES GROUP. 'Resources Group' shall have the
         meaning set forth in the Separation Agreement; provided, however, that
         the term Resources Group shall not include Orion Power Holdings, Inc.
         or any of its subsidiaries."



                                       2
<PAGE>
                  6. The definition of "Resources Stock Value" in Section 1.59
of the Agreement is hereby amended to read as follows:

                  "1.59 RESOURCES STOCK VALUE. `Resources Stock Value' means the
         closing sales price of a share of Resources Common Stock on the New
         York Stock Exchange - Composite Transactions reporting system on the
         Record Date."

                  7. Section 2.03(a) of the Agreement is hereby amended to
reflect that Resources established the Resources Health and Welfare Plans (as
such term is defined in the Agreement) effective January 1,2002.

                  8. Section 2.03(b) of the Agreement is hereby amended to
reflect that Resources established the Resources Savings Plan, effective
February 1, 2002, and the Resources Union Savings Plan effective January 1,
2002.

                  9. Section 2.03(c) of the Agreement is hereby amended to
reflect that Resources established the Resources nonqualified benefit plans
described therein as of January 1, 2002 for all such plans other than the
Benefit Restoration Plan, which Resources established March 1, 2002.

                  10. Section 2.04 of the Agreement is hereby amended to provide
that clause (ii) of such Section shall not apply with respect to any plan if the
former employee's benefit has been transferred to a Resources Plan.

                  11. Section 2.07 of the Agreement is hereby amended to reflect
that Resources may merge, and has merged, its defined contribution Union Plans
into a single Union Plan, effective January 1, 2002.

                  12. Section 2.09 of the Agreement is hereby amended to include
the MRT Welfare Benefit Trust (effective August 31, 2001).



                                       3
<PAGE>
                  13. The first sentence of Section 3.01 of the Agreement is
hereby amended to read as follows:

         "Effective as of March 1, 2001, REI shall amend the Retirement Plan to
         provide that employees who become employed by any member of the
         Resources Croup on or after March 1, 2001 shall not be eligible to
         participate in the Retirement Plan."

                  14. Section 4.01 of the Agreement is hereby amended to reflect
that (1) Resources shall establish, or cause to be established, the Resources
Savings Plan, for non-represented Resources Croup employees, effective as of
February 1, 2002, which shall be a savings plan intended to be qualified under
Code Section 401(a), with a tax exempt trust under Code Section 501(a), and (2)
effective as of March 28, 2002, non-represented Resources Employees (who are not
employees of Reliant Energy Mid-Atlantic ("REMA") shall commence participation
in the Resources Savings Plan (and cease active participation in the REI Savings
Plan as of such date).

                  15. The first sentence of Section 4.02 of the Agreement is
hereby amended to replace "Distribution Date" with "March 1, 2001."

                  16. The last sentence of Section 4.03 of the Agreement is
hereby amended to replace "Distribution Date" with "February 1, 2002."

                  17. Section 4.04 of the Agreement is hereby amended to read as
follows:

         "Notwithstanding the above, account balances of Resources Retired
         Employees, if any, shall be transferred to the Resources Savings Plan
         or Resources Union Savings Plan, as applicable, at such time as the
         amount of assets to be transferred from the REI Savings Plan to the
         Resources Savings Plan and Union Savings Plan is made pursuant to
         Section 4.01."

                  18. Section 6.01(a) of the Agreement is hereby amended to (i)
replace "Distribution Date or such other date as REI and Resources may mutually
agree" with "December 31, 2001 or such other date as REI and Resources may
mutually agree (`Resources Health and Welfare Plan Effective Date')", (ii)
provide that, except as otherwise provided in



                                       4
<PAGE>
Article IV of the Agreement, health and welfare benefits for Resources Employees
shall be the responsibility of Resources after the Resources Health and Welfare
Plan Effective Date of the applicable Resources Health and Welfare Plan, (iii)
replace each subsequent "Distribution Date" with "Resources Health and Welfare
Plan Effective Date" and (iv) add the following new sentence to the end thereof:

         "The foregoing notwithstanding to the contrary, Resources shall
         establish a long term disability plan (`LTD Plan'), effective January
         1, 2002, for Resources Employees; provided, however, that a Resources
         Employee who is determined by the plan administrator of the applicable
         REI LTD Plan to be eligible for, and commences to receive, a benefit
         under the REI LTD Plan prior to July 1, 2002, shall continue to receive
         his or her long-term disability benefit under the applicable REI LTD
         Plan and be the responsibility of REI."

                  19. Sections 6.01(b), 6.02, 6.03 and 6.04 of the Agreement are
hereby amended to replace, as applicable, "Distribution Date" or "Distribution
Date or such other date as REI and Resources may mutually agree upon" with
"Resources Health and Welfare Plan Effective Date."

                  20. Section 6.05 of the Agreement is hereby amended to (i)
replace "Distribution Date" with "Resources Health and Welfare Plan Effective
Date," (ii) provide that, notwithstanding the foregoing clause (i) above, a
Resources Employee or his or her dependant(s) eligible for COBRA on and after
May 1, 2002, shall be the responsibility of Resources and a Resources Employee
eligible for COBRA prior to May 1, 2002, shall remain the responsibility of REI;
provided, however, that the COBRA benefit provided to a REMA employee by RBI
prior to May 1, 2002 shall be provided for such employee on and after January 1,
2003 by Resources and shall be the responsibility of Resources on and after
such date, and (iii) replace "HIPPA" with "HIPAA."



                                       5
<PAGE>
                  21. Article VII of the Agreement is hereby amended to read as
follows:

                                  "ARTICLE VII.

                          EQUITY AND OTHER COMPENSATION

                  7.01 REI OPTIONS.

                  (a) Pre-May 4, 2001 Option Conversion. Outstanding REI Options
granted prior to May 4, 2001 (and certain other Options designated by REI as
being subject to conversion as pre-May 4, 2001 Options) that are unexercised and
unexpired as of the Record Date shall be replaced with two options, subject to
specific country tax and legal requirements, one a New REI Option and one a
Resources Option as follows. In general, a REI Option that qualifies as an
incentive stock option under Section 422 of the Code will be replaced with a New
REI Option and a Resources Option which is intended to qualify as incentive
stock options, provided, however, that in order for incentive stock options to
remain qualified and retain their tax benefits under the Code, the adjustment
formulas described below may be required to be altered. With respect to each New
REI Option, (1) the number of shares of REI Common Stock subject to such New REI
Option shall equal the number of shares of REI Common Stock subject to the REI
Option immediately before the Record Date, and (2) the per-share exercise price
of such New REI Option shall equal the per-share exercise price of the REI
Option immediately prior to the Record Date multiplied by 1 minus a fraction,
the numerator of which is the Distribution Ratio multiplied by the Resources
Stock Value and the denominator of which is the REI Stock Value. With respect to
each Resources Option, (1) the number of shares of Resources Common Stock
subject to such Resources Option, shall equal the number of shares of REI Common
Stock subject to the REI Option immediately before the Record Date multiplied by
the Distribution Ratio, and (2) the per-share exercise price of such Resources
Option shall equal the Resources Stock Value multiplied by a fraction, the
numerator of which is the per-share exercise price of the REI Option immediately
prior to the Record Date and the denominator of which is the REI Stock Value.
The exercise price per share of each such New REI Option and Resources Option
will be determined such that, immediately following the Record Date, the
difference between the exercise price of each option and the fair market value
of the shares underlying each option approximately equals, in the aggregate, the
difference between the exercise price of each REI Option and the fair market
value per share of REI Common Stock (with dividend) immediately prior to the
Record Date. In addition, the ratio of the exercise price of the New REI Options
to the fair market value of REI's Common Stock immediately after the Record
Date, and the ratio of the exercise price of the Resources Options to the fair
market value of Resources' Common Stock immediately after the Record Date, will
both approximately equal the ratio of the exercise price of the REI Options to
the fair market value of REI's Common Stock (with dividend) immediately prior
the Record Date. Employment with Resources will be treated as employment with
REI for purposes of the New REI Options, and employment with REI will be treated
as employment with Resources for purposes of the Resources Options.



                                       6
<PAGE>
Other than the adjustments described in this Section 7.01(a), all other terms
and conditions applicable to the REI Options (including, but not limited to, the
vesting schedule) shall remain applicable to the New REI Options and the
Resources Options following the Record Date, and the Resources Options shall be
issued pursuant to a separate mirror transition option plan adopted specifically
for the purpose of issuing the Resources Options described in this Section 7.01
(a).

                  (b) Post-May 3, 2001 Option Conversion. REI Options that were
issued on or after May 4, 2001 (other than certain designated options described
above in subsection (a) and that are unexercised and unexpired as of the Record
Date) (the `2001 REI Options'), shall be adjusted (as adjusted, the `Adjusted
Company Options') effective as of the Record Date as follows: (1) the number of
shares subject to the Adjusted Company Option shall be equal to a fraction, the
numerator of which is the number of shares of REI Common Stock subject to the
2001 REI Option immediately before the Record Date and the denominator of which
is 1 minus a fraction, the numerator of which is the Distribution Ratio
multiplied by the Resources Stock Value and the denominator of which is the REI
Stock Value; (2) the per-share exercise price of such Adjusted Company Option
shall equal the per-share exercise price of the 2001 REI Option immediately
prior to the Record Date multiplied by 1 minus a fraction, the numerator of
which is the Distribution Ratio multiplied by the Resources Stock Value and the
denominator of which is the REI Stock Value; and (3) other than the adjustments
described above, all other terms and conditions applicable to the 2001 REI
Options (including, but not limited to, the vesting schedule) shall remain
applicable to the Adjusted Company Options following the Record Date.

                  (c) Certain Non-U.S. Optionees. Except as may otherwise be
agreed upon by REI and Resources, this Section 7.01 shall govern the treatment
of REI Options held by Non-U.S. Resources Employees. In the event it is
determined that the local law applicable to any Non-U.S. Optionee requires a
different treatment, REI and Resources shall take such steps as is required to
comply with local law or may cash-out those Options that cannot reasonably be
converted.

                  7.02 REI RESTRICTED SHARES. Performance shares (or bookkeeping
units representing such shares) outstanding under the LICP and the Reliant
Energy, Incorporated Business Unit Performance Share Plan shall vest for the
performance cycle, ending December 31, 2000 and December 31, 2001 according to
the terms and conditions of the applicable Plan. As of the Distribution Date,
the Plan administrator shall convert outstanding performance shares (or
bookkeeping units representing such shares) for the performance cycle ending
December 31, 2002 to a number of time-based restricted shares equal to the
number of performance shares that would have vested if the performance
objectives for the performance cycle were achieved at the maximum level;
provided, however, that for certain executives who voluntarily elected otherwise
the conversion shall be determined based on actual performance. Such time based
restricted shares shall vest if the participant holding such award remains
continuously employed with Resources or REI through December 31, 2002. Holders
of these and other time-based restricted shares granted prior to the year



                                       7
<PAGE>


2001 that are outstanding on the Distribution Date shall receive shares of
Resources Common Stock (or bookkeeping units representing such shares) in the
same ratio as REI shareholders, but such Resources Common Stock shall be subject
to the same time-based vesting schedule and the other terms and conditions of
the applicable Plan under which they were granted.

                  7.03 STOCK PURCHASE PLAN. Effective January 1, 2001, Resources
shall establish a Stock Purchase Plan for the benefit of employees of the
members of the Resources Group which shall be comparable to the plan set forth
in Schedule 7.03.

                  7.04 RESOURCES LONG-TERM INCENTIVE PLAN. Effective as of
January 1, 2001, Resources shall establish the Resources Long-Term Incentive
Plan (`LTIP') for the benefit of employees of the members of the Resources
Group. To the extent applicable to a `covered employee' as defined in Code
Section 162(m), the LTIP is intended to allow for the grant of qualified
performance-based compensation within the meaning of Code Section 162(m).

                  7.05 RESOURCES ANNUAL INCENTIVE COMPENSATION PLAN. Effective
as of January 1, 2001, Resources shall establish the Resources Annual Incentive
Compensation Plan (`AICP') for the benefit of employees of the members of the
Resources Group. To the extent applicable to a `covered employee' as defined in
Code Section 162(m), the AICP is intended to allow for the grant of qualified
performance-based compensation within the meaning of Code Section 162(m)."



                                       8
<PAGE>
                  IN WITNESS WHEREOF, CenterPoint Energy, Inc. and Reliant
Resources, Inc. have caused these presents to be executed by their 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 12th, day of December, 2003.


                                       CENTERPOINT ENERGY, INC.


                                       By: /s/ DAVID M. MCCLANAHAN
                                           -------------------------------------
                                           David M. McClanahan
                                           President and Chief Executive Officer



                                       RELIANT RESOURCES, INC.


                                       By: /s/ R.S. LETBETTER
                                           -------------------------------------