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                                                                     EXHIBIT 4.1


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                          FIRST SUPPLEMENTAL INDENTURE

                        DATED AS OF               , 2001
                                    --------------

                                     BETWEEN

                                NRG ENERGY, INC.

                                    AS ISSUER

                                       AND

                        [------------------------------]

                                   AS TRUSTEE

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                                Table of Contents

<TABLE>
<CAPTION>
                                                                                                 Page

<S>                                                                                            <C>
ARTICLE I DEFINITIONS...............................................................................1

         Section 1.1 Definition of Terms............................................................1

ARTICLE II GENERAL TERMS AND CONDITIONS OF THE DEBENTURES...........................................4

         Section 2.1 Designation and Principal Amount...............................................4
         Section 2.2 Maturity.......................................................................4
         Section 2.3 Form, Payment and Appointment..................................................4
         Section 2.4 Global Debentures..............................................................5
         Section 2.5 Interest.......................................................................6

ARTICLE III REDEMPTION OF THE DEBENTURES............................................................7

         Section 3.1 Tax Event Redemption...........................................................7
         Section 3.2 Redemption Procedures for Debentures...........................................8
         Section 3.3 No Sinking Fund................................................................8
         Section 3.4 Option to Put Debentures upon Failed Secondary Remarketing.....................8
         Section 3.5 Repurchase Procedure for Debentures............................................9

ARTICLE IV EXPENSES.................................................................................9

         Section 4.1 Payment of Expenses............................................................9

ARTICLE V NOTICE...................................................................................10

         Section 5.1 Notice by the Company.........................................................10

ARTICLE VI FORM OF DEBENTURE.......................................................................10

         Section 6.1 Form of Debenture.............................................................10

ARTICLE VII ORIGINAL ISSUE OF DEBENTURES...........................................................21

         Section 7.1 Original Issue of Debentures..................................................21
</TABLE>


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<TABLE>
<S>                                                                                            <C>
ARTICLE VIII MISCELLANEOUS.........................................................................21

         Section 8.1 Ratification of Indenture.....................................................21
         Section 8.2 Trustee Not Responsible for Recitals..........................................21
         Section 8.3 New York Law to Govern........................................................22
         Section 8.4 Separability..................................................................22
         Section 8.5 Counterparts..................................................................22
         Section 8.6 Provisions of Base Indenture Not Applicable...................................22


ARTICLE IX REMARKETING.............................................................................22

         Section 9.1 Initial Remarketing Procedures................................................22
         Section 9.2 Secondary Remarketing Procedures..............................................26

</TABLE>


                                       ii

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         FIRST SUPPLEMENTAL INDENTURE, dated as of _______________, 2001 (the
"First Supplemental Indenture"), between NRG Energy, Inc., a corporation duly
organized and existing under the laws of the State of Delaware (the "Company"),
and [_______________________], as trustee (the "Trustee").

         WHEREAS, the Company executed and delivered the Indenture dated as of
_____________, 2001 (the "Base Indenture") to the Trustee to provide for the
issuance of the Company's debentures, notes, bonds or other evidence of
indebtedness (the "Securities"), to be issued from time to time in one or more
series as might be determined by the Company under the Base Indenture; and

         WHEREAS, pursuant to the terms of the Base Indenture, the Company
desires to provide for the establishment of a new series of its Securities to be
known as its _____% Senior Debentures due 2006 (the "Debentures"), the form and
terms of such Debentures and the terms, provisions and conditions thereof to be
set forth as provided in the Base Indenture and this First Supplemental
Indenture (together, the "Indenture"); and

         WHEREAS, the Company has requested that the Trustee execute and deliver
this First Supplemental Indenture and all requirements necessary to make this
First Supplemental Indenture a valid, binding and enforceable instrument in
accordance with its terms, and to make the Debentures, when executed,
authenticated and delivered by the Company, the valid, binding and enforceable
obligations of the Company, have been done and performed, and the execution and
delivery of this First Supplemental Indenture has been duly authorized in all
respects.

         NOW THEREFORE, in consideration of the purchase and acceptance of the
Debentures by the Holders thereof, and for the purpose of setting forth, as
provided in the Base Indenture, the form and terms of the Debentures, the
Company covenants and agrees with the Company as follows:

                                   ARTICLE I
                                   DEFINITIONS

                 Section 1.1       Definition of Terms

         Unless the context otherwise requires:

             (a) a term defined in the Base Indenture has the same meaning when
         used in this First Supplemental Indenture;


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             (b) a term defined anywhere in this First Supplemental Indenture
         has the same meaning throughout;

             (c) the singular includes the plural and vice versa;

             (d) headings are for convenience of reference only and do not
         affect interpretation;

             (e) the following terms have the meanings given to them in the
         Purchase Contract Agreement (i) Applicable Principal Amount, (ii)
         Authorized Newspaper; (iii) Cash Settlement; (iv) Clearing Agency; (v)
         Clearing Agency Participant; (vi) Corporate Units; (vii) Initial
         Remarketing; (viii) Initial Remarketing Date; (ix) Purchase Contract
         Agent (x) Quotation Agent; (xi) Redemption Price; (xii) Reset Agent;
         (xiii) Reset Announcement Date; (xiv) Reset Rate; (xv) Reset Spread;
         (xvi) Secondary Remarketing; (xvii) Secondary Remarketing Date; (xviii)
         Tax Event; (xix) Treasury Portfolio; (xx) Treasury Portfolio Purchase
         Price; (xxi) Treasury Units; (xxii) Two-Year Benchmark Treasury;
         (xxiii) Two and One-Quarter Year Benchmark Treasury; and (xxiv)
         Underwriting Agreement;

             (f) the following terms have the meanings given to them in this
         Section 1.1(f):

         "Coupon Rate" shall have the meaning set forth in Section 2.5.

         "Custodial Agent" shall have the meaning set forth in the Pledge
Agreement.

         "Debentures" shall have the meaning specified in Section 2.1.

         "Debenture Repayment Price'" shall have the meaning set forth in
Section 3.4.

         "Failed Initial Remarketing" shall have the meaning set forth in
Section 9.1(g).

         "Failed Secondary Remarketing" shall have the meaning set forth in
Section 9.2(h).

         "Global Debentures" shall have the meaning set forth in Section 2.4.



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         "Maturity Date" shall have the meaning specified in Section 2.2.

         "Pledge Agreement" means the Pledge Agreement dated as of ____________,
2001 among the Company, __________________________, as collateral agent (the
"Collateral Agent"), custodial agent and securities intermediary and
______________________________, as purchase contract agent and attorney-in-fact.

         "Purchase Contract" shall have the meaning set forth in the Purchase
Contract Agreement.

         "Purchase Contract Agreement" means the Purchase Contract Agreement
dated as of ________________, 2001, among the Company and ______________, as
purchase contract agent.

         "Purchase Contract Settlement Date" means _________________, 2004.

         "Put-Option" shall have the meaning set forth in Section 3.4.

         "Put-Option Exercise Date" shall have the meaning set forth in Section
3.4.

         "Regular Record Date" means, with respect to any Interest Payment Date
for the Debentures, the close of business on the first day of the month in which
such Interest Payment Date falls.

         "Remarketing Agent" means ______________________________________ or any
successor thereto or replacement Remarketing Agent under the Remarketing
Agreement.

         "Remarketing Agreement" means the Remarketing Agreement, dated as of
__________, 2001, among the Company, __________________________as remarketing
agent and _____________________, as purchase contract agent and
attorney-in-fact.

         "Reset Effective Date" means (i) ________, 2003 in case the interest
rate is reset on the Initial Remarketing Date, or (ii) the Purchase Contract
Settlement Date, in case the interest rate is reset on the Secondary Remarketing
Date.



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         The terms "First Supplemental Indenture," "Base Indenture," and
"Debentures" shall have the respective meanings set forth in the recitals to
this First Supplemental Indenture and the paragraph preceding such recitals.

                                   ARTICLE II
                 GENERAL TERMS AND CONDITIONS OF THE DEBENTURES

                 Section 2.1       Designation and Principal Amount.

         There is hereby authorized a series of Securities designated the ___%
Senior Debentures due 2006, (the "Debentures") limited (except as otherwise
provided in Article II of the Indenture) in aggregate principal amount to
$200,000,000 (or, $230,000,000, if the Underwriters' over-allotment option is
exercised in full). The Debentures may be issued from time to time upon written
order of the Company for the authentication and delivery of Debentures pursuant
to Section 2.2 of the Base Indenture.

                 Section 2.2       Maturity.

         The date upon which the Debentures shall become due and payable at
final maturity, together with any accrued and unpaid interest, is ___________,
2006 (the "Maturity Date").

                 Section 2.3       Form, Payment and Appointment

         Except as provided in Section 2.4, the Debentures shall be issued in
fully registered certificated form without interest coupons, bearing identical
terms. Principal of and premium, if any, and interest on the Debentures will be
payable, the transfer of such Debentures will be registrable and such Debentures
will be exchangeable for Debentures bearing identical terms and provisions at
the office or agency of the Company maintained for such purpose as described
below; provided, however, that payment of interest may be made at the option of
the Company by check mailed to the Holder at such address as shall appear in the
Securities Register or by wire transfer to an account appropriately designated
by the Holder entitled to payment.

         The Company hereby designates the Borough of Manhattan, The City of New
York as the place of payment ("Place of Payment") for the Debentures, and the
office or agency maintained by the Company in such Place of Payment for the
purposes



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<PAGE>   8

contemplated by this Section 2.3 shall initially be the Corporate Trust
Office of the Trustee in c/o _____________________________________________.

         The Security Registrar, transfer agent and Paying Agent for the
Debentures shall be ____________________________.

         The Debentures shall be issuable in denominations of $25 and integral
multiples of $25 in excess thereof.

         The Debentures may be issued, in whole or in part, in permanent global
form and, if issued in permanent global form, the U.S. Depositary shall be The
Depository Trust Company or such other depositary as any officer of the Company
may from time to time designate.

                 Section 2.4       Global Debentures.

             (a) Unless and until it is exchanged for the Debentures in
         registered form, one or more global Debentures in principal amount
         equal to the aggregate principal amount of all outstanding Debentures
         ("Global Debentures") may be transferred, in whole but not in part,
         only to the Clearing Agency or a nominee of the Clearing Agency, or to
         a successor Clearing Agency selected or approved by the Company or to a
         nominee of such successor Clearing Agency.

             (b) If at any (i) time the Clearing Agency notifies the Company
         that it is unwilling or unable to continue as a Clearing Agency for the
         Global Debentures and no successor Clearing Agency shall have been
         appointed within 90 days after such notification, (ii) the Clearing
         Agency at any time ceases to be a clearing agency registered under the
         Securities Exchange Act of 1934 at any time the Clearing Agency is
         required to be so registered to act as such Clearing Agency and no
         successor Clearing Agency shall have been appointed within 90 days
         after the Company becoming aware of the Clearing Agency's ceasing to be
         so registered, (iii) the Company, in its sole discretion, determines
         that the Global Debentures shall be so exchangeable or (iv) there shall
         have occurred and be continuing an Event of Default, the Company will
         execute, and subject to Article II of the Base Indenture, the Trustee,
         upon written notice from the Company, will authenticate and deliver the
         Debentures in definitive registered form without coupons, in authorized
         denominations, and in an aggregate principal amount equal to the
         principal amount of the Global Debenture in exchange for such Global
         Debenture.



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         Upon exchange of the Global Debenture for such Debentures in definitive
         registered form without coupons, in authorized denominations, the
         Global Debenture shall be cancelled by the Trustee. Such Debentures in
         definitive registered form issued in exchange for the Global Debenture
         shall be registered in such names and in such authorized denominations
         as the Clearing Agency, pursuant to instructions from its direct or
         indirect participants or otherwise, shall instruct the Trustee. The
         Trustee shall deliver such Securities to the Clearing Agency for
         delivery to the Persons in whose names such Securities are so
         registered.

                Section 2.5        Interest.

             (a) Each Debenture will bear interest initially at the rate of ___%
         per annum (the "Coupon Rate") from the original date of issuance
         through and including the day immediately preceding the Reset Effective
         Date and at the Reset Rate thereafter until the principal thereof is
         paid or duly made available for payment and shall bear interest, to the
         extent permitted by law, compounded quarterly, on any overdue principal
         and premium, if any, and on any overdue installment of interest at the
         Coupon Rate through and including the day immediately preceding the
         Reset Effective Date and at the Reset Rate thereafter, payable
         quarterly in arrears on __________, __________, ___________ and
         _____________ of each year (each, an "Interest Payment Date")
         commencing on _____________, 2001, to the Person in whose name such
         Debenture, or any predecessor Debenture, is registered at the close of
         business on the Regular Record Date for such interest installment.

             (b) The interest rate on the Debentures will be reset on the
         Initial Remarketing Date to the applicable Reset Rate (which Reset Rate
         will be effective on and after _________, 2003) except in the event of
         a Failed Initial Remarketing. In the event of a Failed Initial
         Remarketing, the interest rate on the Debentures will be reset on the
         Secondary Remarketing Date to the applicable Reset Rate (which Reset
         Rate will be effective on and after the Purchase Contract Settlement
         Date). On the applicable Reset Announcement Date, the applicable Reset
         Spread and the Two-Year Benchmark Treasury or Two and One-Quarter Year
         Benchmark Treasury, as applicable, will be announced by the Company. On
         the Business Day immediately following such Reset Announcement Date,
         the Holders of Debentures will be notified of such Reset Spread and
         Two-Year Benchmark Treasury or Two and One-Quarter Year Benchmark
         Treasury, as applicable, by the Company. Such



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         notice shall be sufficiently given to such Holders of Debentures if
         published in an Authorized Newspaper.

             (c) Not later than seven calendar days nor more than 15 calendar
         days immediately preceding the applicable Reset Announcement Date, the
         Company will request that the Clearing Agency or its nominee (or any
         successor Clearing Agency or its nominee) notify the Holders of
         Debentures of such Reset Announcement Date and, in the case of a
         Secondary Remarketing, the procedures to be followed by such holders of
         Debentures wishing to settle the related Purchase Contracts with
         separate cash on the Business Day immediately preceding the Purchase
         Contract Settlement Date.

             (d) The amount of interest payable for any period will be computed
         on the basis of a 360-day year consisting of twelve 30-day months.
         Except as provided in the following sentence, the amount of interest
         payable for any period other than a full quarterly period for which
         interest is computed, will be computed on the basis of the actual
         number of days elapsed in such a 90-day period. In the event that any
         date on which interest is payable on the Debentures is not a Business
         Day, then payment of interest payable on such date will be made on the
         next succeeding day which is a Business Day (and without any interest
         or other payment in respect of any such delay), except that, if such
         Business Day is in the next succeeding calendar year, such payment
         shall be made on the immediately preceding Business Day, in each case
         with the same force and effect as if made on such date.

                                  ARTICLE III
                          REDEMPTION OF THE DEBENTURES

                 Section 3.1       Tax Event Redemption.

         If a Tax Event shall occur and be continuing, the Company may, at its
option, redeem the Debentures in whole (but not in part) at any time at a price
per Debenture equal to the Redemption Price. Installments of interest on
Debentures which are due and payable on or prior to the date of redemption (the
"Tax Event Redemption Date") will be payable to the Holders of the Debentures
registered as such at the close of business on the Regular Record Date. If,
following the occurrence of a Tax Event prior to the Purchase Contract
Settlement Date, the Company exercises its option to redeem the Debentures, the
Company shall appoint the Quotation Agent to assemble the Treasury Portfolio in
consultation with the Company. Notice of any redemption will be mailed at least
30 days but not more than 60 days before the Tax



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Event Redemption Date to each registered Holder of the Debentures to be repaid
at its registered address. Unless the Company defaults in payment of the
Redemption Price, on and after the Tax Event Redemption Date interest shall
cease to accrue on the Debentures.

                 Section 3.2       Redemption Procedures for Debentures.

         Payment of the Redemption Price to each Holder of Debentures shall be
made by the Company, no later than 12:00 noon, New York City time, on the Tax
Event Redemption Date, by check or wire transfer in immediately available funds
at such place and to such account as may be designated by each such Holder of
Debentures, including the Trustee or the Collateral Agent, as the case maybe. If
the Trustee holds immediately available funds sufficient to pay the Redemption
Price of the Debentures, then, on such Tax Event Redemption Date, such
Debentures will cease to be outstanding and interest thereon will cease to
accrue, whether or not such Debentures have been received by the Company, and
all other rights of the Holder in respect of the Debentures shall terminate and
lapse (other than the right to receive the Redemption Price upon delivery of
such Debentures but without interest on such Redemption Price).

                 Section 3.3       No Sinking Fund.

         The Debentures are not entitled to the benefit of any sinking fund.

                 Section 3.4       Option to Put Debentures upon Failed
Secondary Remarketing.

         If a Failed Secondary Remarketing (as described in Section 5.4(b) of
the Purchase Contract Agreement and incorporated herein by reference) has
occurred, each holder of Debentures who holds such Debentures on the day
immediately following the Purchase Contract Settlement Date shall have the right
(the "Put Option") on the Business Day immediately following the Purchase
Contract Settlement Date, to put such Debentures to the Company on _______, 2004
(the "Put Option Exercise Date"), upon at least three Business Days prior
notice, at a repayment price equal to the principal amount of such Debentures
plus an amount equal to the accrued and unpaid interest thereon to the date of
payment (the "Debenture Repayment Price").



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                 Section 3.5       Repurchase Procedure for Debentures.

             (a) In order for the Debentures to be repurchased on the Put Option
         Exercise Date, the Trustee must receive on or prior to 5:00 p.m. New
         York City time on the third Business Day immediately preceding the Put
         Option Exercise Date, at its Corporate Trust Office or at an office or
         agency maintained by the Company in the Borough of Manhattan, The City
         of New York as contemplated by Section 2.3 hereof, the Debentures to be
         repurchased with the form entitled "Option to Elect Repayment" on the
         reverse of or otherwise accompanying such Debentures duly completed.
         Any such notice received by the Trustee shall be irrevocable. All
         questions as to the validity, eligibility (including time of receipt)
         and acceptance of the Debentures for repayment shall be determined by
         the Company, whose determination shall be final and binding.

             (b) Payment of the Debenture Repayment Price shall be made through
         the Trustee, subject to the Trustee's receipt of payment from the
         Company in accordance with the terms of the Indenture, no later than
         12:00 noon, New York City time, on the Put Option Exercise Date, and to
         such account as may be designated. If the Trustee holds immediately
         available funds sufficient to pay the Debenture Repayment Price of
         Debentures presented for repayment, then, immediately prior to the
         close of business on the Put Option Exercise Date, such Debentures will
         cease to be outstanding and Interest thereon will cease to accrue,
         whether or not such Debentures have been received by the Company, and
         all other rights of the Holder in respect of the Debentures, including
         the Holder's right to require the Company to repay such Debentures,
         shall terminate and lapse (other than the right to receive the
         Debenture Repayment Price upon delivery of such Debentures but without
         interest on such Debenture Repayment Price). Neither the Trustee nor
         the Company will be required to register or cause to be registered the
         transfer of any Debenture for which repayment has been elected.

                                   ARTICLE IV
                                    EXPENSES

                 Section 4.1       Payment of Expenses.

         In connection with the offering, sale and issuance of the Debentures to
the Holders, the Company, in its capacity as borrower with respect to the
Debentures shall pay all costs and expenses relating to the offering, sale and
issuance of the



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Debentures, including commissions to the underwriters payable pursuant to the
Underwriting Agreement and compensation of the Trustee under the Indenture in
accordance with the provisions of Section 5.6 of the Base Indenture.

                                   ARTICLE V
                                     NOTICE

                 Section 5.1       Notice by the Company.

         The Company shall give prompt written notice to a Responsible Officer
of the Trustee of any fact known to the Company that would prohibit the making
of any payment of monies to or by the Trustee in respect of the Debentures.
Notwithstanding any of the provisions of the Base Indenture and this First
Supplemental Indenture, the Trustee shall not be charged with knowledge of the
existence of any facts that would prohibit the making of any payment of monies
to or by the Trustee in respect of the Debentures; provided, however, that if
the Trustee shall not have received the notice provided for in this Article V at
least two Business Days prior to the date upon which by the terms hereof any
money may become payable for any purpose (including, without limitation, the
payment of the principal of (or premium, if any) or interest on any Debenture),
then, anything herein contained to the contrary notwithstanding, the Trustee
shall have full power and authority to receive such money and to apply the same
to the purposes for which they were received, and shall not be affected by any
notice to the contrary that may be received by it within two Business Days prior
to such date.

                                   ARTICLE VI
                                FORM OF DEBENTURE

                 Section 6.1       Form of Debenture.

         The Debentures and the Trustee's Certificate of Authentication to be
endorsed thereon are to be substantially in the following forms, with such
changes therein as the officers of the Company executing the Debentures (by
manual or facsimile signature) may approve, such approval to be conclusively
evidenced by their execution thereof:

                           (FORM OF FACE OF DEBENTURE)

IF THE DEBENTURE IS TO BE A GLOBAL DEBENTURE, INSERT - THIS DEBENTURE IS A
GLOBAL DEBENTURE WITHIN THE MEANING OF THE



                                       10
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INDENTURE HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF THE CLEARING
AGENCY OR A NOMINEE OF THE CLEARING AGENCY. THIS DEBENTURE IS EXCHANGEABLE FOR
DEBENTURES REGISTERED IN THE NAME OF A PERSON OTHER THAN THE CLEARING AGENCY OR
ITS NOMINEE ONLY IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE, AND NO
TRANSFER OF THIS DEBENTURE (OTHER THAN A TRANSFER OF THIS DEBENTURE AS A WHOLE
BY THE CLEARING AGENCY TO A NOMINEE OF THE CLEARING AGENCY OR BY A NOMINEE OF
THE CLEARING AGENCY TO THE CLEARING AGENCY OR ANOTHER NOMINEE OF THE CLEARING
AGENCY OR TO A SUCCESSOR CLEARING AGENCY OR TO A NOMINEE OF SUCH SUCCESSOR) MAY
BE REGISTERED EXCEPT IN LIMITED CIRCUMSTANCES.

UNLESS THIS DEBENTURE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE
DEPOSITORY TRUST COMPANY (55 WATER STREET, NEW YORK, NEW YORK) TO THE ISSUER OR
ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT AND ANY DEBENTURE
ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS REQUESTED
BY AN AUTHORIZED REPRESENTATIVE OF TIE DEPOSITORY TRUST COMPANY AND ANY PAYMENT
HEREON IS MADE TO CEDE & CO., ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE
OR OTHERWISE BY A PERSON IS WRONGFUL SINCE TIE REGISTERED OWNER HEREOF, CEDE &
CO., HAS AN INTEREST HEREIN.

CUSIP No.________________
$________________________


                                NRG ENERGY, INC.
                              ___% SENIOR DEBENTURE
                              DUE ___________, 2006

         NRG ENERGY, INC., a Delaware corporation (the "Company", which term
includes any successor corporation under the Indenture hereinafter referred to),
for value received, hereby promises to pay to _________, as Trustee or
registered assigns, the principal sum of_________________ Dollars ($___________)
on __________, 2006 (such date is hereinafter referred to as the "Maturity
Date"), and to pay interest on said principal sum from ___________, 2001 or from
the next



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<PAGE>   15

recent date to which interest has been paid or duly provided for, quarterly in
arrears on __________, __________, ___________ and ___________ of each year
(each such date, an "Interest Payment Date"), commencing on ___________, 2001
initially at the rate of ___% per annum through and including the day
immediately preceding the Reset Effective Date and at the Reset Rate thereafter
until the principal hereof shall have been paid or duly made available for
payment and, to the extent permitted by law, to pay interest, compounded
quarterly, on any overdue principal and premium, if any, and on any overdue
installment of interest at the rate per annum of ___% through and including the
day immediately preceding the Reset Effective Date and at the Reset Rate
thereafter. The amount of interest payable on any Interest Payment Date shall be
computed on the basis of a 360-day year consisting of twelve 30-day months and,
except as provided in the Indenture (as defined below), the amount of interest
payable for any period shorter than a full quarterly period for which interest
is computed will be computed on the basis of the actual number of days elapsed
in such 90-day period. In the event that any date on which interest is payable
on this Debenture is not a Business Day, then payment of interest payable on
such date will be made on the next succeeding day that is a Business Day (and
without any interest or other payment in respect of any such delay), except
that, if such Business Day is in the next succeeding calendar year, such payment
shall be made on the immediately preceding Business Day, in each case with the
same force and effect as if made on such Interest Payment Date. The interest
installment so payable, and punctually paid or duly provided for, on any
Interest Payment Date will, as provided in the Indenture, be paid to the person
in whose name this Debenture (or one or more predecessor Securities) is
registered at the close of business on the Regular Record Date for such interest
installment which shall be the close of business on the first day of the month
in which such Interest Payment Date falls. Any such interest installment not
punctually paid or duly provided for on any Interest Payment Date shall
forthwith cease to be payable to the registered Holders at the close of business
on such Regular Record Date and may be paid to the Person in whose name this
Debenture (or one or more predecessor Securities) is registered at the close of
business on a special record date to be fixed by the Trustee for the payment of
such defaulted interest, notice whereof shall be given to the registered Holders
of this series of Debentures not less than 10 days prior to such special record
date, or may be paid at any time in any other lawful manner not inconsistent
with the requirements of any securities exchange on which the Debentures may be
listed, and upon such notice as may be required by such exchange, all as more
fully provided in the Indenture. The principal of (and premium, if any) and the
interest on this Debenture shall be payable at the office or agency of the
Company maintained for that purpose in the Borough of Manhattan, the City of New
York in any coin or currency of the United States of America that at the time of
payment is legal tender



                                       12
<PAGE>   16

for payment of public and private debts; provided, however, that payment of
interest may be made at the option of the Company by check mailed to the
registered Holder at such address as shall appear in the Security Register or by
wire transfer to an account appropriately designated by the Holder entitled
thereto.

         The indebtedness evidenced by this Debenture is, to the extent provided
in the Indenture, senior and unsecured and will rank in right of payment on
parity with all other senior unsecured obligations of the Company.

         This Debenture shall not be entitled to any benefit under the Indenture
hereinafter referred to or be valid or obligatory for any purpose until the
Certificate of Authentication shall have been signed by or on behalf of the
Trustee.

         The provisions of this Debenture are continued on the reverse side
hereof and such continued provisions shall for all purposes have the same effect
as though fully set forth at this place.


                                       13
<PAGE>   17


         IN WITNESS WHEREOF, the Company has caused this instrument to be
executed.

Dated:  _________, 2001

                                                     NRG ENERGY, INC., as Issuer

                                                     By:________________________
                                                        Name:
                                                        Title:

Attest:

By:____________________________
   Name:
   Title:

                          CERTIFICATE OF AUTHENTICATION

This is one of the Debentures of the series of Debentures described in the
within-mentioned Indenture.

Dated _________________________________

[______________________________________],
as Trustee

By_____________________________________
           Authorized Signatory


                                       14
<PAGE>   18

                         (FORM OF REVERSE OF DEBENTURE)


         This Debenture is one of a duly authorized series of Securities of the
Company (herein sometimes referred to as the "Debentures"), issued and to be
issued in one or more series under and pursuant to an Indenture dated as of
__________, 2001 (the "Base Indenture") between the Company and
_______________________, as Trustee (the "Trustee," which term includes any
successor trustee under the Indenture), as supplemented by a First Supplemental
Indenture, dated as of ________, 2001 (the "First Supplemental Indenture")
between the Company and the Trustee (the Base Indenture as so supplemented, the
"Indenture"), to which Indenture and all indentures supplemental thereto
reference is hereby made for a description of the rights, limitations of rights,
obligations, duties and immunities thereunder of the Trustee, the Company and
the Holders of the Debentures. By the terms of the Indenture, the Securities are
issuable in series that may vary as to amount, date of maturity, rate of
interest and in other respects as provided in the Indenture. This series of
Securities is limited in aggregate principal amount as specified in said First
Supplemental Indenture.

         If a Tax Event shall occur and be continuing, the Company may, at its
option, redeem the Debentures in whole (but not in part) at any time at a price
per Debenture equal to the Redemption Price. The Redemption Price shall be paid
to each Holder of the Debentures by the Company, no later than 12:00 noon, New
York City time, on the Tax Event Redemption Date, by check or wire transfer in
immediately available funds, at such place and to such account as may be
designated by each such Holder.

         The Debentures are not entitled to the benefit of any sinking fund.

         If a Failed Secondary Remarketing (as described in Section 5.4(b) of
the Purchase Contract Agreement and incorporated herein by reference) has
occurred, each holder of Debentures who holds such Debentures on the day
immediately following the Purchase Contract Settlement Date shall have the right
(the "Put Option") on the Business Day immediately following the Purchase
Contract Settlement Date, to put such Debentures to the Company, on
____________, 2004 (the "Put Option Exercise Date"), upon at least three
Business Days prior notice), at a repayment price equal to the principal amount
of this Debenture plus an amount equal to the accrued and unpaid interest
thereon to the date of payment (the "Debenture Repayment Price").



                                       15
<PAGE>   19

         In order for the Debentures to be so repurchased, the Trustee must
receive, on or prior to 5:00 p.m. New York City Time on the third Business Day
immediately preceding the Put Option Exercise Date, at its Corporate Trust
Office, or at an office or agency maintained by the Company in the Borough of
Manhattan, The City of New York as contemplated by Section 2.3 of the First
Supplemental Indenture, the Debentures to be repurchased with the form entitled
"Option to Elect Repayment" on the reverse of or otherwise accompanying such
Debentures duly completed. Any such notice received by the Trustee shall be
irrevocable. All questions as to the validity, eligibility (including time of
receipt) and acceptance of the Debentures for repayment shall be determined by
the Company, whose determination shall be final and binding. The payment of the
Debenture Repayment Price in respect of such Debentures shall be made no later
than 12:00 noon, New York City time, on the Put Option Exercise Date.

         In case an Event of Default, as defined in the Indenture, shall have
occurred and be continuing, the principal of all of the Debentures may be
declared, and upon such declaration shall become, due and payable (or, in
certain circumstances shall ipso facto become due and payable), in the manner,
with the effect and subject to the conditions provided in the Indenture.

         The Indenture contains provisions permitting, with certain exceptions
therein provided, the Company and the Trustee, with the consent of the Holders
of not less than a majority in aggregate principal amount of the Outstanding
Securities of each series affected to execute supplemental indentures for the
purpose of, among other things, adding any provisions to or changing or
eliminating any of the provisions of the Indenture or of any supplemental
indenture or of modifying the rights of the Holders of the Securities. The
Indenture also contains provisions permitting the Holders of a majority in
aggregate principal amount of the Securities of any series at the time
Outstanding, on behalf of all of the Holders of all Securities of such series,
to waive a Default or Event of Default with respect to such series and its
consequences, except a Default or Event of Default in the payment of the
principal of or premium, if any, or interest on any of the Securities of such
series or in respect of a covenant or other provision which, under the terms of
the Indenture, cannot be modified or amended without the consent of the Holder
of each Outstanding Security of such series affected. Any such consent or waiver
by the registered Holder of this Debenture (unless revoked as provided in the
Indenture) shall be conclusive and binding upon such Holder and upon all future
Holders of this Debenture and of any Debenture issued in exchange for or in
place hereof (whether by registration of transfer or otherwise), irrespective of
whether or not any notation of such consent or waiver is made upon this
Debenture.



                                       16
<PAGE>   20

         No reference herein to the Indenture and no provision of this Debenture
or of the Indenture shall alter or impair the obligation of the Company, which
is absolute and unconditional, to pay the principal of and premium, if any, and
interest on this Debenture at the time and place and at the rate and in the
money herein prescribed.

         As provided in the Indenture and subject to certain limitations therein
set forth, this Debenture is transferable by the registered Holder hereof on the
Security Register of the Company, upon surrender of this Debenture for
registration of transfer at the office or agency of the Company maintained for
such purpose in the Borough of Manhattan, The City of New York, accompanied by a
written instrument or instruments of transfer in form satisfactory to the
Company or the Trustee duly executed by the registered Holder hereof or his
attorney duly authorized in writing, and thereupon one or more new Debentures of
authorized denominations and for the same aggregate principal amount will be
issued to the designated transferee or transferees. No service charge will be
made for any such transfer, but the Company may require payment of a sum
sufficient to cover any transfer tax or similar governmental charge payable in
relation thereto.

         Prior to due presentment for registration of transfer of this
Debenture, the Company, the Trustee, any Paying Agent and the Security Registrar
may deem and treat the registered Holder hereof as the absolute owner hereof
(whether or not this Debenture shall be overdue and notwithstanding any notice
of ownership or writing hereon made by anyone other than the Security Registrar)
for the purpose of receiving payment of or on account of the principal hereof
and premium, if any, and interest due hereon and for all other purposes, and
neither the Company nor the Trustee nor any Paying Agent nor any Security
Registrar shall be affected by any notice to the contrary.

         No recourse shall be had for the payment of the principal of or the
interest on this Debenture, or for any claim based hereon, or otherwise in
respect hereof, or based on or in respect of the Indenture, against any
incorporator, shareholder, officer or director, past, present or future, as
such, of the Company or of any predecessor or successor corporation, whether by
virtue of any constitution, statute or rule of law, or by the enforcement of any
assessment or penalty or otherwise, all such liability being, by the acceptance
hereof and as part of the consideration for the issuance hereof, expressly
waived and released.

         The Indenture imposes certain limitations on the ability of the Company
to, among other things, merge or consolidate with any other Person or sell,
assign,



                                       17
<PAGE>   21

transfer or lease all or substantially all of its properties or assets, and
requires that the Company comply with certain further covenants. All such
covenants and limitations are subject to a number of important qualifications
and exceptions. The Company must report periodically to the Trustee on
compliance with the covenants in the Indenture.

         The Debentures of this series are issuable only in registered form
without coupons in denominations of $25 and any integral multiple thereof. As
provided in the Indenture and subject to certain limitations therein set forth,
Debentures are exchangeable for a like aggregate principal amount of Debentures
of a different authorized denomination, as requested by the Holder surrendering
the same.

         All terms used in this Debenture that are defined in the Indenture
shall have the meanings assigned to them in the Indenture.

         The Debentures are subject to defeasance and covenant defeasance upon
the terms and subject to the conditions set forth in the Indenture.

         This Debenture shall be governed by and construed in accordance with
the internal laws of the State of New York.


                                       18
<PAGE>   22

                            OPTION TO ELECT REPAYMENT

         The undersigned hereby irrevocably requests and instructs the Company
to repay $____ principal amount of the within Debenture, pursuant to its terms,
on the "Put Option Exercise Date," together with any interest thereon accrued
but unpaid to the date of repayment, to the undersigned at:

(Please print or type name and address of the undersigned)

and to issue to the undersigned, pursuant to the terms of the Indenture, a new
Debenture or Debentures representing the remaining aggregate principal amount of
this Debenture.

For this Option to Elect Repayment to be effective, this Debenture with the
Option to Elect Repayment duly completed must be received by the Trustee at c/o
___________________________________________, no later than 5:00 p.m. on the
third Business Day immediately preceding ___________, 2004.


Dated: _______________________      Signature:_________________________________

                                    Signature Guarantee:_______________________


Note: The signature to this Option to Elect Repayment must correspond with the
name as written upon the face of the within Debenture without alteration or
enlargement or any change whatsoever.

                               SIGNATURE GUARANTEE

         Signatures must be guaranteed by an "eligible guarantor institution"
meeting the requirements of the Registrar, which requirements include membership
or participation in the Security Transfer Agent Medallion Program ("STAMP") or
such other "signature guarantee program" as may be determined by the Registrar
in addition to, or in substitution for, STAMP, all in accordance with the
Securities Exchange Act of 1934, as amended.


                                       19
<PAGE>   23

                                   ASSIGNMENT

FOR VALUE RECEIVED, the undersigned assigns and transfers this Debenture to:
_______________________________________________________________________________
_______________________________________________________________________________

(Insert assignee's social security or tax identification number)
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________

(Insert address and zip code of assignee)

and irrevocably appoints

_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
agent to transfer this Debenture on the books of the Company. The agent may
substitute another to act for him or her.

Date: _____________________________________

                                      Signature:
                                      _________________________________Signature
                                      Guarantee:___________________________

(Sign exactly as your name appears on the other side of this Debenture)

                               SIGNATURE GUARANTEE

         Signatures must be guaranteed by an "eligible guarantor institution"
meeting the requirements of the Registrar, which requirements include membership
or participation in the Security Transfer Agent Medallion Program ("STAMP") or
such


                                       20
<PAGE>   24
other "signature guarantee program" as may be determined by the Registrar in
addition to, or in substitution for, STAMP, all in accordance with the
Securities Exchange Act of 1934, as amended.

                                  ARTICLE VII
                          ORIGINAL ISSUE OF DEBENTURES

                 Section 7.1       Original Issue of Debentures.

         Debentures in the aggregate principal amount of $200,000,000 (or,
$230,000,000, if the Underwriters' over-allotment option is exercised in full)
may from time to time, upon execution of this First Supplemental Indenture, be
executed by the Company and delivered to the Trustee for authentication, and the
Trustee shall thereupon authenticate and deliver said Debentures to or upon the
written order of the Company pursuant to Section 2.2 of the Base Indenture
without any further action by the Company.

         The Company shall file with the Trustee promptly at the end of each
calendar year (i) a written notice specifying the amount of original issue
discount (including daily rates and accrual periods) accrued on Outstanding
Debentures as of the end of the year and (ii) such other specific information
relating to such original issue discount as may then be relevant under the
Internal Revenue Code of 1986, as amended from time to time.

                                  ARTICLE VIII
                                  MISCELLANEOUS

                 Section 8.1       Ratification of Indenture.

         The Indenture as supplemented by this First Supplemental Indenture, is
in all respects ratified and confirmed, and this First Supplemental Indenture
shall be deemed part of the Indenture in the manner and to the extent herein and
therein provided.

                 Section 8.2       Trustee Not Responsible for Recitals.

         The recitals herein contained are made by the Company and not by the
Trustee, and the Trustee assumes no responsibility for the correctness thereof.
The Trustee makes no representation as to the validity or sufficiency of this
First Supplemental Indenture.



                                       21
<PAGE>   25

                 Section 8.3       New York Law to Govern.

         THIS FIRST SUPPLEMENTAL INDENTURE AND EACH DEBENTURE SHALL, PURSUANT TO
SECTION 5-1401 OF THE NEW YORK GENERAL OBLIGATIONS LAW, BE GOVERNED BY THE LAW
OF THE STATE OF NEW YORK, WITHOUT REFERENCE TO THE CHOICE OF LAW PROVISIONS
THEREOF (OTHER THAN SUCH SECTION 5-1401).

                 Section 8.4       Separability.

         In case any one or more of the provisions contained in this First
Supplemental Indenture or in the Debentures shall for any reason be held to be
invalid, illegal or unenforceable in any respect, then, to the extent permitted
by law, such invalidity, illegality or unenforceability shall not affect any
other provisions of this First Supplemental Indenture or of the Debentures, but
this First Supplemental Indenture and the Debentures shall be construed as if
such invalid or illegal or unenforceable provision had never been contained
herein or therein.

                 Section 8.5       Counterparts.

         This First Supplemental Indenture may be executed in any number of
counterparts each of which shall be an original, but such counterparts shall
together constitute but one and the same instrument.

                 Section 8.6       Provisions of Base Indenture Not Applicable.

         The provisions of Section 3.9 and Article XI of the Base Indenture
shall not apply to the Debentures.

                                   ARTICLE IX
                                   REMARKETING

                 Section 9.1       Initial Remarketing Procedures

             (a) The Company will request, not later than seven nor more than 15
         calendar days prior to the Initial Remarketing Date that the Clearing
         Agency notify the Holders of the Debentures and the Holders of
         Corporate Units and Treasury Units of the Initial Remarketing.

                                       22
<PAGE>   26

             (b) Not later than 5:00 P.M., New York City time, on the second
         Business Day immediately preceding the Initial Remarketing Date, each
         Holder of the Debentures not constituting components of Corporate Units
         may elect to have Debentures held by such Holder remarketed. Holders of
         Debentures that are not a component of Corporate Units shall give
         notice of their election to have such Debentures remarketed to the
         Custodial Agent pursuant to the Pledge Agreement. Any such notice shall
         be irrevocable after 5:00 P.M., New York City time, on the second
         Business Day immediately preceding the Initial Remarketing Date and may
         not be conditioned upon the level at which the Reset Rate is
         established. Promptly after 5:30 P.M., New York City time, on such
         second Business Day, the Trustee, based on the notices received by it
         prior to such time (including notices from the Purchase Contract Agent
         as to Purchase Contracts for which Cash Settlement has been elected),
         shall notify the Company and the Remarketing Agent of the number of
         Debentures to be tendered for remarketing. Under Section 5.3 of the
         Purchase Contract Agreement, Debentures that constitute components of
         Corporate Units will be remarketed as provided therein and in this
         Section 9.1. The Debentures constituting components of Corporate Units
         shall be deemed tendered, notwithstanding any failure by the Holder of
         such Corporate Units to deliver or properly deliver such Debentures to
         the Remarketing Agent for purchase.

             (c) The right of each Holder to have Debentures tendered for
         purchase shall be limited to the extent that (i) the Remarketing Agent
         conducts a remarketing pursuant to the terms of the Remarketing
         Agreement, (ii) Debentures tendered have not been called for
         redemption, (iii) the Remarketing Agent is able to find a purchaser or
         purchasers for tendered Debentures at a price per Debenture such that
         the aggregate price for the Applicable Principal Amount of Debentures
         is not less than 100% of the Treasury Portfolio Purchase Price, and
         (iv) such purchaser or purchasers deliver the purchase price therefor
         to the Remarketing Agent as and when required.

             (d) On the Initial Remarketing Date, the Remarketing Agent shall
         use reasonable efforts to remarket, at a price per Debenture such that
         the aggregate price for the Applicable Principal Amount of Debentures
         is equal to approximately 100.5% of the Treasury Portfolio Purchase
         Price, Debentures tendered or deemed tendered for purchase.


                                       23
<PAGE>   27

             (e) If there are no Corporate Units outstanding and none of the
         Holders elect to have Debentures held by them remarketed, the Reset
         Rate shall be the rate determined by the Reset Agent, subject to the
         terms of the Remarketing Agreement, as the rate that would have been
         established had a remarketing been held on the Initial Remarketing
         Date.

             (f) If the Remarketing Agent has determined that it will be able to
         remarket all Debentures tendered or deemed tendered prior to 4:00 P.M.,
         New York City time, on the Initial Remarketing Date, the Reset Agent,
         subject to the terms of the Remarketing Agreement, shall determine the
         Reset Rate.

             (g) If, by 4:00 P.M., New York City time, on the Initial
         Remarketing Date, the Remarketing Agent is unable to remarket all
         Debentures tendered or deemed tendered for purchase or if the Initial
         Remarketing shall not have occurred because a condition precedent to
         the Remarketing shall not have been fulfilled, a failed remarketing
         ("Failed Initial Remarketing") shall be deemed to have occurred and the
         Remarketing Agent shall so advise by telephone the Collateral Agent,
         Company, Trustee, and Clearing Agency.

             (h) By approximately 4:30 P.M., New York City time, on the Initial
         Remarketing Date, provided that there has not been a Failed Initial
         Remarketing, the Remarketing Agent shall advise, by telephone (i) the
         Collateral Agent, the Company, Trustee, and Clearing Agency of the
         Reset Rate determined in the Initial Remarketing and the aggregate
         principal amount of Debentures sold in the Initial Remarketing, (ii)
         each purchaser (or the Clearing Agency Participant thereof) of the
         Reset Rate and the aggregate principal amount of Debentures such
         purchaser is to purchase and (iii) each purchaser to give instructions
         to its Clearing Agency Participant to pay the purchase price on
         ___________, 2003 in same day funds against delivery of the Debentures
         purchased through the facilities of the Clearing Agency.

             (i) In accordance with the Clearing Agency's normal procedures, on
         ________, 2003, the transactions described above with respect to each
         Debenture tendered for purchase and sold in the Initial Remarketing
         shall be executed through the Clearing Agency, and the accounts of the
         respective Clearing Agency Participants shall be debited and credited
         and such Debentures delivered by book entry as necessary to effect
         purchases and sales of such Debentures. The Clearing Agency shall make
         payment in accordance with its normal procedures.



                                       24
<PAGE>   28

             (j) If any Holder selling Debentures in the Initial Remarketing
         fails to deliver such Debentures, the Clearing Agency Participant of
         such selling Holder and of any other Person that was to have purchased
         Debentures in the Initial Remarketing may deliver to any such other
         Person an aggregate principal amount of Debentures that is less than
         the aggregate principal amount of Debentures that otherwise was to be
         purchased by such Person. In such event, the aggregate principal amount
         of Debentures to be so delivered shall be determined by such Clearing
         Agency Participant, and delivery of such lesser aggregate principal
         amount of Debentures shall constitute good delivery.

             (k) The Remarketing Agent is not obligated to purchase any
         Debentures in the Initial Remarketing or otherwise. Neither the Trust,
         any Trustee, the Company nor the Remarketing Agent shall be obligated
         in any case to provide funds to make payment upon tender of Debentures
         for remarketing.

             (l) The tender and settlement procedures set in this Section 9.1,
         including provisions for payment by purchasers of Debentures in the
         Initial Remarketing, shall be subject to modification, notwithstanding
         any provision to the contrary set forth herein, to the extent required
         by the Clearing Agency or if the book-entry system is no longer
         available for the Debentures at the time of the Initial Remarketing, to
         facilitate the tendering and remarketing of Debentures in certificated
         form. In addition, the Remarketing Agent may, notwithstanding any
         provision to the contrary set forth herein, modify the settlement
         procedures set forth herein in order to facilitate the settlement
         process.

             (m) Anything herein to the contrary notwithstanding, the Reset Rate
         shall in no event exceed the maximum rate permitted by applicable law
         and, as provided in the Remarketing Agreement, neither the Remarketing
         Agent nor the Reset Agent shall have any obligation to determine
         whether there is any limitation under applicable law on the Reset Rate
         or, if there is any such limitation, the maximum permissible Reset Rate
         on the Debentures and they shall rely solely upon written notice from
         the Company (which the Company agrees to provide prior to the 10th
         Business Day before ________, 2003) as to whether or not there is any
         such limitation and, if so, the maximum permissible Reset Rate.




                                       25
<PAGE>   29

                 Section 9.2       Secondary Remarketing Procedures.

             (a) If a Failed Initial Remarketing has occurred, the Company will
         request, not later than seven nor more than 15 calendar days prior to
         the Secondary Remarketing Date that the Clearing Agency notify the
         Holders of the Debentures and the Holders of Corporate Units and
         Treasury Units of the Secondary Remarketing and of the procedures that
         must be followed if a Holder of Debentures wishes to exercise such
         Holder's rights with respect to the Put Option if there is a Failed
         Secondary Remarketing.

             (b) Not later than 5:00 P.M., New York City time, on the second
         Business Day immediately preceding the Secondary Remarketing Date, each
         Holder of the Debentures may elect to have Debentures held by such
         Holder remarketed. Under Section 5.4 of the Purchase Contract
         Agreement, Holders of Corporate Units that do not give notice of
         intention to make a Cash Settlement of their related Purchase Contracts
         shall be deemed to have consented to the disposition of the Debentures
         constituting a component of such Corporate Units. Holders of Debentures
         that are not a component of Corporate Units shall give notice of their
         election to have such Debentures remarketed to the Custodial Agent
         pursuant to the Pledge Agreement. Any such notice shall be irrevocable
         after 5:00 P.M., New York City time, on the second Business Day
         immediately preceding the Secondary Remarketing Date and may not be
         conditioned upon the level at which the Reset Rate is established.
         Promptly after 5:30 P.M., New York City time, on such second Business
         Day, the Trustee, based on the notices received by it prior to such
         time (including notices from the Purchase Contract Agent as to Purchase
         Contracts for which Cash Settlement has been elected), shall notify the
         Company and the Remarketing Agent of the number of Debentures to be
         tendered for remarketing.

             (c) If any Holder of Corporate Units does not give a notice of its
         intention to make a Cash Settlement or gives a notice of election to
         tender Debentures as described in Section 9.2(b), the Debentures of
         such Holder shall be deemed tendered, notwithstanding any failure by
         such Holder to deliver or properly deliver such Debentures to the
         Remarketing Agent for purchase.

             (d) The right of each Holder to have Debentures tendered for
         purchase shall be limited to the extent that (i) the Remarketing Agent
         conducts a remarketing pursuant to the terms of the Remarketing
         Agreement, (ii)



                                       26
<PAGE>   30

         Debentures tendered have not been called for redemption, (iii) the
         Remarketing Agent is able to find a purchaser or purchasers for
         tendered Debentures at a price of not less than 100% of the principal
         amount thereof, and (iv) such purchaser or purchasers deliver the
         purchase price therefor to the Remarketing Agent as and when required.

             (e) If a Failed Initial Remarketing has occurred, on the Secondary
         Remarketing Date, the Remarketing Agent shall use reasonable efforts to
         remarket, at a price equal to approximately 100.5% of the aggregate
         principal amount thereof, Debentures tendered or deemed tendered for
         purchase.

             (f) If none of the Holders elect or are deemed to have elected to
         have Debentures held by them remarketed, the Reset Rate shall be the
         rate determined by the Reset Agent, subject to the terms of the
         Remarketing Agreement, as the rate that would have been established had
         a remarketing been held on the Secondary Remarketing Date.

             (g) If the Remarketing Agent has determined that it will be able to
         remarket all Debentures tendered or deemed tendered prior to 4:00 P.M.,
         New York City time, on the Secondary Remarketing Date, the Reset Agent
         shall, subject to the terms of the Remarketing Agreement, determine the
         Reset Rate.

             (h) If, by 4:00 P.M., New York City time, on the Secondary
         Remarketing Date, the Remarketing Agent is unable to remarket all
         Debentures tendered or deemed tendered for purchase or if the Secondary
         Remarketing shall not have occurred because a condition precedent to
         the Secondary Remarketing shall not have been fulfilled, a failed
         remarketing ("Failed Secondary Remarketing") shall be deemed to have
         occurred and the Remarketing Agent shall so advise by telephone the
         Collateral Agent, Company, Trustee, and Clearing Agency.

             (i) By approximately 4:30 P.M., New York City time, on the
         Secondary Remarketing Date, provided that there has not been a Failed
         Secondary Remarketing, the Remarketing Agent shall advise, by telephone
         (i) the Collateral Agent, the Company, Trustee, and Clearing Agency of
         the Reset Rate determined in the Secondary Remarketing and the
         aggregate principal amount of Debentures sold in the Secondary
         Remarketing, (ii) each purchaser (or the Clearing Agency Participant
         thereof) of the Reset Rate and the aggregate principal amount of
         Debentures such purchaser is to purchase



                                       27
<PAGE>   31

         and (iii) each purchaser to give instructions to its Clearing Agency
         Participant to pay the purchase price on the Purchase Contract
         Settlement Date in same day funds against delivery of the Debentures
         purchased through the facilities of the Clearing Agency.

             (j) In accordance with the Clearing Agency's normal procedures, on
         the Purchase Contract Settlement Date, the transactions described above
         with respect to each Debenture tendered for purchase and sold in the
         Secondary Remarketing shall be executed through the Clearing Agency,
         and the accounts of the respective Clearing Agency Participants shall
         be debited and credited and such Debentures delivered by book entry as
         necessary to effect purchases and sales of such Debentures. The
         Clearing Agency shall make payment in accordance with its normal
         procedures.

             (k) If any Holder selling Debentures in the Secondary Remarketing
         fails to deliver such Debentures, the Clearing Agency Participant of
         such selling Holder and of any other Person that was to have purchased
         Debentures in the Secondary Remarketing may deliver to any such other
         Person an aggregate principal amount of Debentures that is less than
         the aggregate principal amount of Debentures that otherwise was to be
         purchased by such Person. In such event, the aggregate principal amount
         of Debentures to be so delivered shall be determined by such Clearing
         Agency Participant, and delivery of such lesser aggregate principal
         amount of Debentures shall constitute good delivery.

             (l) The Remarketing Agent is not obligated to purchase any
         Debentures in the Secondary Remarketing or otherwise. Neither the
         Trust, any Trustee, the Company nor the Remarketing Agent shall be
         obligated in any case to provide funds to make payment upon tender of
         Debentures for remarketing.

             (m) The tender and settlement procedures set in this Section 9.2,
         including provisions for payment by purchasers of Debentures in the
         Secondary Remarketing, shall be subject to modification,
         notwithstanding any provision to the contrary set forth herein, to the
         extent required by the Clearing Agency or if the book-entry system is
         no longer available for the Debentures at the time of the Secondary
         Remarketing, to facilitate the tendering and remarketing of Debentures
         in certificated form. In addition, the Remarketing Agent may,
         notwithstanding any provision to the contrary set forth herein, modify
         the settlement procedures set forth herein in order to facilitate the
         settlement process.



                                       28
<PAGE>   32

             (n) Anything herein to the contrary notwithstanding, the Reset Rate
         shall in no event exceed the maximum rate permitted by applicable law
         and, as provided in the Remarketing Agreement, neither the Remarketing
         Agent nor the Reset Agent shall have any obligation to determine
         whether there is any limitation under applicable law on the Reset Rate
         or, if there is any such limitation, the maximum permissible Reset Rate
         on the Debentures and they shall rely solely upon written notice from
         the Company (which the Company agrees to provide prior to the 10th
         Business Day before the Purchase Contract Settlement Date) as to
         whether or not there is any such limitation and, if so, the maximum
         permissible Reset Rate.


                                       29
<PAGE>   33


         IN WITNESS WHEREOF, the parties hereto have caused this First
Supplemental Indenture to be duly executed by their respective officers
thereunto duly authorized, on the date or dates indicated in the acknowledgments
and as of the day and year first above written.


                                      NRG ENERGY, INC., as Issuer


                                      By: __________________________
                                      Name:
                                      Title:


Attest:


By: ________________________
Name:
Title:

                                      _______________________________,
                                      as Trustee


                                      By: ____________________________
                                      Name:
                                      Title:


Attest:


By: ________________________
Name:
Title:



                                       30