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                                                                     EXHIBIT 4.1


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                          THIRD SUPPLEMENTAL INDENTURE

                            Dated as of July 16, 2001

                                       to

                                    INDENTURE

                           Dated as of March 13, 2001

                                     between

                                NRG ENERGY, INC.

                                       and

                              THE BANK OF NEW YORK,

                                   as Trustee


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         THIRD SUPPLEMENTAL INDENTURE, dated as of July 16, 2001 (this "Third
Supplemental Indenture"), to the Indenture, dated as of March 13, 2001 (the
"Base Indenture"), between NRG ENERGY, INC., a Delaware corporation (the
"Company"), and THE BANK OF NEW YORK, a New York banking corporation (the
"Trustee"), as supplemented by the First Supplemental Indenture, dated as of
March 13, 2001 (the "First Supplemental Indenture"), between the Company and the
Trustee and the Second Supplemental Indenture, dated as of April 5, 2001 (the
"Second Supplemental Indenture"), between the Company and the Trustee.

         WHEREAS, the Company and the Trustee have heretofore executed and
delivered the Base Indenture to provide for the issuance from time to time of
Securities (as defined in the Base Indenture) of the Company, to be issued in
one or more Series (as defined in the Base Indenture);

         WHEREAS, Sections 2.1, 2.2 and 7.1 of the Base Indenture provide, among
other things, that the Company and the Trustee may enter into indentures
supplemental to the Base Indenture for, among other things, (i) the purpose of
establishing the designation, form, terms and provisions of Securities of any
Series as permitted by Sections 2.1, 2.2 and 7.1 of the Base Indenture and (ii)
the purpose of reopening a Series of Securities for issuances of additional
Securities of such Series;

         WHEREAS, the Company (i) desires the issuance of a new separate Series
of Securities to be designated as hereinafter provided and desires to reopen for
issuance of additional Securities the Series of Securities designated the 8.625%
Senior Notes due 2031 established by the Second Supplemental Indenture (the
"Senior Notes due 2031") and (ii) has requested the Trustee to enter into this
Third Supplemental Indenture for the purpose of establishing the designation,
form, terms and provisions of the Securities of such new Series and reopening
the Senior Notes due 2031;

         WHEREAS, all action on the part of the Company necessary to authorize
the issuance of said Securities under the Base Indenture and this Third
Supplemental Indenture has been duly taken.

         NOW, THEREFORE, THIS THIRD SUPPLEMENTAL INDENTURE WITNESSETH:

         That, in order to establish the designation, form, terms and provisions
of or reopen for issuance, and to authorize the authentication and delivery of,
said Securities, and in consideration of the acceptance of said Securities by
the Holders thereof and of other good and valuable consideration, the receipt
and sufficiency of which are hereby acknowledged, the parties hereto hereby
agree as follows:


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                                   ARTICLE I

                                  DEFINITIONS

         (a) Capitalized terms used herein and not otherwise defined herein
shall have the respective meanings ascribed thereto in the Base Indenture.

         (b) The rules of interpretation set forth in the Base Indenture shall
be applied hereto as if set forth in full herein.

         (c) For all purposes of this Third Supplemental Indenture, except as
otherwise expressly provided or unless the context otherwise requires, the
following terms shall have the following respective meanings (such meanings
shall apply equally to both the singular and plural forms of the respective
terms):

         "Change of Control" means the occurrence of one or more of the
following events: (i) Xcel or its successors ceases to own a majority of the
outstanding Voting Stock of the Issuer, (ii) at any time following the
occurrence of the event described in the preceding clause (i), a Person or group
(as that term is used in Section 13(d)(3) of the Exchange Act) of Persons (other
than Xcel) shall have become the beneficial owner directly or indirectly, or
shall have acquired the absolute power to direct the vote, of more than 35% of
the outstanding Voting Stock of the Issuer or (iii) during any twelve-month
period, individuals who at the beginning of such period constitute the Board of
Directors (together with any new directors whose election or nomination was
approved by a majority of the directors then in office who were either directors
at the beginning of such period or who were previously so approved) shall cease
for any reason to constitute a majority of the Board of Directors.
Notwithstanding the foregoing, a Change of Control shall be deemed not to have
occurred with respect to a Series of Securities if one or more of the above
events occurs or circumstances exist and, after giving effect thereto, the
Securities of such Series are rated Investment Grade.

         "Comparable Treasury Issue" means the United States Treasury security
selected by Banc of America Securities LLC or Deutsche Banc Alex. Brown Inc., or
any of their respective affiliates as having a maturity comparable to the
remaining term of the Notes that would be utilized, at the time of selection and
in accordance with customary financial practice, in pricing new issues of
corporate debt securities of comparable maturity to the remaining term of the
Senior Notes due 2006.




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         "Comparable Treasury Price" means the average of three Reference
Treasury Dealer Quotations obtained by the Trustee in respect of the Senior
Notes due 2006 to be redeemed on the applicable redemption date.

         "Make Whole Amount" means, with respect to the Senior Notes due 2006 at
any time, the sum of the present values of the Remaining Scheduled Payments
discounted, on a semiannual basis (assuming a 360 day year consisting of twelve
30-day months), at a rate equal to the Treasury Rate plus 25 basis points. The
Make Whole Amount shall be computed as of the third Business Day prior to the
applicable redemption date, and certified, by an Investment Banker.

         "Notes" means the Senior Notes due 2006 and the Senior Notes due 2031.

         "Reference Treasury Dealer Quotation" means, with respect to each
Reference Treasury Dealer and any redemption date, the average, as determined by
the Trustee, of the bid and asked prices for the Comparable Treasury Issue
(expressed in each case as a percentage of its principal amount) quoted in
writing to t he Trustee by a Reference Treasury Dealer at 3:30 p.m., New York
City time, on the third Business Day preceding the redemption date.

         "Reference Treasury Dealers" means Banc of America Securities LLC and
Deutsche Banc Alex. Brown Inc. (so long as they continue to be primary U.S.
Government securities dealers) and any two other primary U.S. Government
securities dealers chosen by the Company. If Banc of America Securities LLC or
Deutsche Banc Alex. Brown Inc. ceases to be a primary U.S. Government securities
dealer, the Company will appoint in its place another nationally recognized
investment banking firm that is a primary U.S. Government securities dealer.

         "Remaining Scheduled Payments" means, with respect to each Senior Note
due 2006 that the Company is redeeming, the remaining scheduled payments of the
principal and interest that would be due after the related redemption date if
such Senior Note due 2006 were not redeemed. However, if the redemption date is
not a scheduled interest payment date with respect to that Senior Note due 2006,
the amount of the next succeeding scheduled interest payment on that Senior Note
due 2006 will be reduced by the amount of interest accrued on such Senior Note
due 2006 to the redemption date.

         "Senior Notes due 2006" shall have the meaning ascribed thereto in
Section 2.1(a) hereof.






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         "Senior Notes due 2031" shall have the meaning ascribed thereto in the
recitals hereof.

         "Treasury Rate" means, with respect to any redemption date, an annual
rate equal to the semiannual equivalent yield to maturity of the Comparable
Treasury Issue, assuming a price for the Comparable Treasury Issue (expressed as
a percentage of its principal amount) equal to the Comparable Treasury Price for
the redemption date. The semiannual equivalent yield to maturity will be
computed as of the third Business Day immediately preceding the redemption date.


                                   ARTICLE II

           GENERAL TERMS AND CONDITIONS OF THE SENIOR NOTES DUE 2006

         SECTION 2.1 Designation and Principal Amount.

         (a) There is hereby authorized a new separate Series of Securities
designated the 6.75% Senior Notes due 2006 (the "Senior Notes due 2006").

         (b) The aggregate principal amount of the Senior Notes due 2006 shall
be limited to $340,000,000 (except that such Series of Securities may be
re-opened for issuance of additional Securities as provided in Article II of the
Base Indenture).

         (c) The Senior Notes due 2006 may be issued from time to time upon
written order of the Company to the Trustee for the authentication and delivery
of the Senior Notes due 2006 pursuant to Section 2.2 of the Base Indenture.

         (d) The Senior Notes due 2006 shall have and be subject to such other
terms as provided in the Base Indenture and shall be evidenced by one or more
Securities of that Series in the form of Exhibit A to the Base Indenture.

         (e) The Senior Notes due 2006 shall be issuable in minimum
denominations of $100,000 and integral multiples of $1,000 in excess thereof.

         SECTION 2.2 Maturity. The date upon which the Senior Notes due 2006
shall become due and payable at final maturity, together with any accrued and
unpaid interest, is July 15, 2006 (the "2006 Notes Maturity Date").



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         SECTION 2.3 Interest.

         (a) The Senior Notes due 2006 will bear interest at the 2006 Notes
Interest Rate (as defined below) from July 16, 2001, until the principal thereof
becomes due and payable. Interest on the Senior Notes due 2006 will be payable
semi-annually in arrears on January 15 and July 15 of each year, commencing
January 15, 2002, to the Person in whose name any such Senior Note due 2006 or
any predecessor Note is registered, at the close of business on the regular
record date for such interest installment, which, in the case of a Global
Security, shall be the close of business on the January 1 and July 1 next
preceding such Interest Payment Date. Notwithstanding the foregoing sentence, if
the Notes are no longer in book-entry only form, the regular record dates for
the Notes shall be the January 1 and July 1 prior to the applicable Interest
Payment Date.

         (b) The interest rate in respect of the Senior Notes due 2006 will be
6.75% per annum (the "2006 Notes Interest Rate").

         (c) In the event that any date on which interest is payable on the
Senior Notes due 2006 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, with
the same force and effect as if made on such date, and no interest shall accrue
on the amount so payable from the period from and after such Interest Payment
Date or Maturity Date, as the case may be (each date on which interest is
actually payable, an "Interest Payment Date").

         SECTION 2.4 Global Securities.

     The Senior Notes due 2006 shall be issued in the form of one or more Global
Securities in an aggregate principal amount equal to the aggregate principal
amount of all outstanding Senior Notes due 2006, to be registered in the name of
the U.S. Depositary, or its nominee, and delivered by the Trustee to or upon the
order of the U.S. Depositary for crediting to the accounts of its participants
pursuant to the written instructions of the Company. The Company upon any such
presentation shall execute one or more Global Securities in such aggregate
principal amount and deliver the same to the Trustee for authentication and
delivery in accordance with the Base Indenture and this Third Supplemental
Indenture. Payments on Senior Notes due 2006 issued as one or more Global
Securities will be made to the U.S. Depositary.



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                                  ARTICLE III

                    REDEMPTION OF THE SENIOR NOTES DUE 2006

         SECTION 3.1 Optional Redemption of the Senior Notes due 2006.

         The Company at its option may, at any time, redeem the Senior Notes due
2006, in whole or in part, upon payment of a redemption price equal to (A) the
greater of (i) 100% of the principal amount of the Senior Notes due 2006 to be
redeemed and (ii) the Make Whole Amount, plus (B) accrued and unpaid interest,
if any, on the principal amount of Senior Notes due 2006 being redeemed to the
redemption date.

         SECTION 3.2 No Sinking Fund.

         The Senior Notes due 2006 are not entitled to the benefit of any
sinking fund.

                                   ARTICLE IV

                     REOPENING OF THE SENIOR NOTES DUE 2031

         SECTION 4.1 Reopening of the Senior Notes due 2031. The Senior Notes
due 2031 are hereby reopened and there is hereby authorized $160,000,000
principal amount of additional Senior Notes due 2031 (the "Additional 2031
Notes"), which shall rank equally in all respects with the Senior Notes due 2006
authorized by and issued under the Second Supplemental Indenture (the "Original
2031 Notes") in all respects, shall form a single series of $500,000,000
principal amount with the Original 2031 Notes, with the same CUSIP number, and
shall have the same terms as the Original 2031 Notes as set forth in the Second
Supplemental Indenture. Interest on the Additional 2031 Notes shall accrue from
April 5, 2001. The Additional 2031 Notes shall be in a form identical to the
form of the Original 2031 Notes except that the date of original issuance will
be July 16, 2001. The Additional 2031 Notes may be issued from time to time upon
written order of the Company to the Trustee for the authentication and delivery
of the Additional 2031 Notes pursuant to Section 2.2 of the Base Indenture. All
references to the Senior Notes due 2006 herein, in the Second Supplemental
Indenture and in any Senior Notes due 2006 shall be deemed to include the
Additional 2031 Notes issued hereunder.



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                                    ARTICLE V

                             ORIGINAL ISSUE OF NOTES

         SECTION 5.1 Original Issue of Senior Notes due 2006.

         The Senior Notes due 2006 in the aggregate principal amount of
$340,000,000 may, upon execution of this Third Supplemental Indenture, be
executed by the Company and delivered to the Trustee for authentication, and the
Trustee shall thereupon authenticate and deliver said Notes to or upon the
written order of the Company pursuant to Section 2.2 of the Base Indenture
without any further action of the Company.

         SECTION 5.2 Original Issue of Senior Notes due 2031.

         The Additional 2031 Notes in the aggregate principal amount of
$160,000,000 may, upon execution of this Third Supplemental Indenture, be
executed by the Company and delivered to the Trustee for authentication, and the
Trustee shall thereupon authenticate and deliver said Notes to or upon the
written order of the Company pursuant to Section 2.2 of the Base Indenture
without any further action of the Company.


                                   ARTICLE VI

                                 MISCELLANEOUS

         SECTION 6.1 Ratification of Base Indenture, First Supplemental
Indenture and Second Supplemental Indenture.

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

         SECTION 6.2 Trustee Not Responsible for Recitals.

         The recitals contained herein and in the Notes, except with respect to
the Trustee's certificates of authentication, shall be taken as the statements
of the Company, and the Trustee assumes no responsibility for the correctness of
the same.



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The Trustee makes no representations as to the validity or sufficiency of this
Third Supplemental Indenture or of the Notes.

         SECTION 6.3 Governing Law.

         THIS THIRD SUPPLEMENTAL INDENTURE AND EACH NOTE OF EACH SERIES CREATED
HEREUNDER 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 6.4 Separability.

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

         SECTION 6.5 Counterparts.

         This Third Supplemental Indenture may be executed in any number of
counterparts, each of which when so executed shall be deemed to be an original,
but all such counterparts shall together constitute but one and the same
instrument.




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         IN WITNESS WHEREOF, the parties have caused this Third Supple-mental
Indenture to be duly executed by their respective officers thereunto duly
authorized as of the date first above written.

                                   NRG ENERGY, INC.


                                   By:
                                      ------------------------------------------
                                      Name:
                                      Title:

                                   THE BANK OF NEW
                                   YORK, as Trustee By: Name: Title:


                                   By:
                                      ------------------------------------------
                                      Name:
                                      Title: