Exhibit 99.1


                                                                  EXECUTION COPY


                                FIRST SUPPLEMENT

                                     TO THE

                           PURCHASE CONTRACT AGREEMENT

                            DATED AS OF JUNE 6, 2002

                                      AMONG

                                NRG ENERGY, INC.,

                                XCEL ENERGY INC.

                                       AND

                              THE BANK OF NEW YORK,

                           AS PURCHASE CONTRACT AGENT





                                                                                                       

ARTICLE I             DEFINITIONS................................................................................3

         Section 1.1       Definition of Terms...................................................................3

ARTICLE II            CONCERNING THE MERGER......................................................................3

         Section 2.1       Xcel Energy as Issuer of Common Stock upon Settlement.................................3

         Section 2.2       Acceptance by Agent...................................................................3

ARTICLE III           CONCERNING SETTLEMENT......................................................................3

         Section 3.1       Purchase Contract Settlement..........................................................3

         Section 3.2       Settlement Rate.......................................................................4

ARTICLE IV            MISCELLANEOUS..............................................................................4

         Section 4.1       Ratification of Purchase Contract Agreement...........................................4

         Section 4.2       Effectiveness.........................................................................5

         Section 4.3       Securities Deemed Conformed...........................................................5

         Section 4.4       Governing Law.........................................................................5

         Section 4.5       Separability..........................................................................5

         Section 4.6       Counterparts..........................................................................5











         THIS FIRST SUPPLEMENT TO THE PURCHASE CONTRACT AGREEMENT, dated as of
June 6, 2002 (this "Supplemental Agreement"), among NRG Energy, Inc., a Delaware
corporation (the "Company"), Xcel Energy Inc., a Minnesota corporation ("Xcel
Energy"), and The Bank of New York, a New York banking corporation, acting as
purchase contract agent for the Holders of Securities from time to time (the
"Agent").

         WHEREAS, the Company and the Agent executed and delivered a Purchase
Contract Agreement, dated as of March 13, 2001 (the "Purchase Contract
Agreement"), to provide for the execution and delivery of the Purchase Contracts
and Certificates related to the Corporate Units and the Treasury Units
(collectively, the "Securities");

         WHEREAS, pursuant to the Certificate of Ownership and Merger, Merging
NRG Merger Corporation Into NRG Energy, Inc., dated as of June 3, 2002 (the
"Merger Certificate"), the Company merged with and into NRG Merger Corporation
with the Company being the surviving corporation (the "Merger");

         WHEREAS, the Merger Certificate provides that, at the effective time of
the Merger (the "Effective Time"), each share of Common Stock of the Company
that was publicly held immediately prior to the Effective Time was converted
into, and was cancelled in exchange for, the right to receive 0.50 shares of
Common Stock of Xcel Energy, par value $2.50 per share ("Xcel Energy Common
Stock"), the associated stock purchase rights and cash in lieu of fractional
shares;

         WHEREAS, Section 9.1 of the Purchase Contract Agreement permits the
Company to merge with another corporation provided certain terms and conditions
are satisfied;

         WHEREAS, Section 5.6(c) of the Purchase Contract Agreement provides
that in the event of a Reorganization Event the Person formed thereby shall
execute and deliver to the Agent an agreement supplemental to the Purchase
Contract Agreement providing that the Holders of each Outstanding Security shall
have the rights provided by Section 5.6 and for adjustments for subsequent
events that are as nearly equivalent as may be practicable to the adjustments
provided for in Section 5.6 of the Purchase Contract Agreement.

         WHEREAS, Section 8.1 of the Purchase Contract Agreement authorizes the
Company and the Agent to enter into a supplemental agreement without the consent
of any Holders to, among other things, make provision with respect to the rights
of Holders pursuant to the requirements of Section 5.6(c) of the Purchase
Contract Agreement;

         WHEREAS, the Company has requested that the Agent execute and deliver
this Supplemental Agreement.

         NOW THEREFORE, in consideration of their mutual promises, Xcel Energy
and the Company covenant and agree with the Agent as follows:








                             ARTICLE I DEFINITIONS

SECTION 1.1 DEFINITION OF TERMS. Unless the context otherwise requires:

     (a)  a term defined in the Purchase Contract Agreement has the same meaning
          when used in this Supplemental Agreement;

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

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

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

                        ARTICLE II CONCERNING THE MERGER

SECTION 2.1 XCEL ENERGY AS ISSUER OF COMMON STOCK UPON SETTLEMENT.

     (a)  The parties hereby agree that, from and after the Effective Time, Xcel
          Energy shall issue and deliver the number of shares of Xcel Energy
          Common Stock which is sufficient to settle the Purchase Contracts as
          provided in Article III of this Supplemental Agreement, against
          payment in full of the Purchase Price in the manner set forth in the
          Purchase Contract Agreement and Section 2.1(b) hereof.

     (b)  The Company hereby agrees that it will immediately forward to Xcel
          Energy all funds received by it under Sections 5.4, 5.9 or otherwise
          under the Purchase Contract Agreement for payment of the Purchase
          Price upon settlement of the Purchase Contract for the shares of Xcel
          Energy Common Stock to be so issued.

SECTION 2.2 ACCEPTANCE BY AGENT. The Agent accepts this Supplemental Agreement
and agrees to execute its duties and responsibilities as hereby supplemented
upon the terms and conditions set forth in the Purchase Contract Agreement,
including without limitation the terms and provisions defining and limiting the
liabilities and responsibilities of the Agent, which terms and provisions shall
in like manner define and limit its liabilities and responsibilities in the
performance of its duties created by the Purchase Contract Agreement as hereby
supplemented; and without limiting the generality of the foregoing, the Agent
shall not be responsible in any manner whatsoever for or with respect to any of
the recitals or statements contained herein, all of which recitals or statements
are made solely by Xcel Energy and the Company, or for or with respect to the
validity or sufficiency of this Supplemental Agreement or any of the terms or
provisions hereof and Xcel Energy and NRG affirm their rights and
responsibilities with respect to the Agent under Section 7.07(3) of the Purchase
Contract Agreement.

                       ARTICLE III CONCERNING SETTLEMENT

SECTION 3.1 PURCHASE CONTRACT SETTLEMENT.

     (a)  NRG and Xcel Energy understand and agree that, pursuant to Section
          5.6(c) of the Purchase Contract Agreement, the Merger constitutes a
          Reorganization Event as a result


                                       3






          of which as of the Effective Time the Settlement Rate was adjusted
          such that each Holder of Securities will receive:

          (i)  on the Purchase Contract Settlement Date with respect to each
               Purchase Contract forming a part thereof the number of shares of
               Xcel Energy Common Stock receivable pursuant to the Merger
               (without any interest thereon, and without any right to dividends
               or distribution thereon which have a record date that is prior to
               the Purchase Contract Settlement Date) by a holder of the number
               of shares of the Company's Common Stock that would have been
               issuable on account of each Purchase Contract if the Purchase
               Contract Settlement Date had occurred immediately prior to the
               Effective Time, or

          (ii) on the Early Settlement Date with respect to each Purchase
               Contract forming a part thereof the number of shares of Xcel
               Energy Common Stock receivable pursuant to the Merger (without
               any interest thereon, and without any right to dividends or
               distribution thereon which have a record date that is prior to
               the Early Settlement Date) by a holder of the number of shares of
               the Company's Common Stock that would have been issuable on
               account of each Purchase Contract if the Early Settlement Date
               had occurred immediately prior to the Effective Time;

         subject in the case of both clauses (i) and (ii) to any further
         adjustments in the Settlement Rate under Article V of the Purchase
         Contract Agreement prior to settlement. Attached as Exhibit A hereto is
         an Officer's Certificate, pursuant to Section 5.7(a)(i) of the Purchase
         Contract Agreement, which sets forth the method of calculation of the
         Settlement Rate as of the Effective Time, as adjusted for the Merger.

     (b)  NRG and Xcel Energy hereby agree that, subject to the other provisions
          of this Supplemental Agreement from and after the Effective Time, the
          provisions of the Purchase Contract Agreement and the Purchase
          Contracts that refer to the delivery of "Common Stock" of the Company,
          including without limitation Sections 5.4, 5.5, 5.9, 5.10, 10.3 and
          10.4 of the Purchase Contract Agreement, relate to Xcel Energy Common
          Stock by operation of Section 5.6(c) of the Purchase Contract
          Agreement.

SECTION 3.2 SETTLEMENT RATE. In accordance with the last four sentences of
Section 5.6(c) of the Purchase Contract Agreement, the Settlement Rate shall be
adjusted for events subsequent to the Effective Time, in a manner that is as
nearly equivalent as may be practicable to the adjustments provided for in
Section 5.6 of the Purchase Contract Agreement, as if Xcel Energy was the
original "Company" and Xcel Energy Common Stock was the original "Common Stock"
under the provisions of Section 5.6 of the Purchase Contract Agreement.

                            ARTICLE IV MISCELLANEOUS

SECTION 4.1 RATIFICATION OF PURCHASE CONTRACT AGREEMENT. The Purchase Contract
Agreement, as supplemented by this Supplemental Agreement, is in all respects
ratified and confirmed, and this Supplemental Agreement shall be deemed part of
the Purchase Contract Agreement in the manner and to the extent herein and
therein provided.


                                       4






SECTION 4.2 EFFECTIVENESS. This Supplemental Agreement shall become a legally
effective and binding instrument upon the execution and delivery hereof by all
parties hereto.

SECTION 4.3 SECURITIES DEEMED CONFORMED. As of the Effective Time, the
provisions of each Security then outstanding shall be deemed to be conformed,
without the necessity for any reissuance or exchange of such Security or any
other action on the part of the Holders, Xcel Energy, the Company or Agent, so
as to reflect this Supplemental Agreement.

SECTION 4.4 GOVERNING LAW. This Supplement and the rights and obligations of the
parties hereunder shall be governed by and construed in accordance with the laws
of the State of New York, including without limitation, Section 5-1401 of the
New York General Obligations Law.

SECTION 4.5 SEPARABILITY. If any one or more of the provisions contained in this
Supplemental Agreement or in the Securities 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 Supplemental
Agreement or of the Securities, but this Supplemental Agreement and the
Securities shall be construed as if such invalid or illegal or unenforceable
provision had never been contained herein or therein.

SECTION 4.6 COUNTERPARTS. This Supplement may be executed in any number of
counterparts, all of which taken together shall constitute one and the same
instrument.

                            [SIGNATURE PAGES FOLLOW]


                                       5






         IN WITNESS WHEREOF, this First Supplement to the Purchase Contract
Agreement is executed as of the date first set forth above.



                                       NRG ENERGY, INC.


                                       By: /s/  C. Adam Carte
                                           -------------------------------------
                                           Name:  C. Adam Carte
                                           Title: Treasurer



                                       XCEL ENERGY INC.


                                       By: /s/  Paul E. Pender
                                           -------------------------------------
                                           Name:  Paul E. Pender
                                           Title: Vice President and Treasurer



                                       THE BANK OF NEW YORK,
                                       as Agent


                                       By: /s/  Paul J. Schmalzel
                                           -------------------------------------
                                           Name:  Paul J. Schmalzel
                                           Title: Vice President



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                                                                       Exhibit A


                              OFFICER'S CERTIFICATE
                               OF NRG ENERGY, INC.
                        UNDER SECTIONS 5.7(a)(i) AND 9.1
                                     OF THE
                           PURCHASE CONTRACT AGREEMENT

THE UNDERSIGNED, C. Adam Carte, the Vice President and Treasurer of NRG Energy,
Inc., a Delaware corporation (the "Company"), hereby certifies:

     (a)  Accompanying this Certificate is the duly executed Supplemental
          Purchase Contract Agreement (the "Supplemental Agreement"), dated as
          of June 6, 2002, among the Company, Xcel Energy Inc., a Minnesota
          corporation ("Xcel Energy"), and The Bank of New York, as purchase
          contract agent (the "Agent"), which is effective as of the Effective
          Time of the Merger of NRG Merger Corporation, an indirect,
          wholly-owned subsidiary of Xcel Energy (the "Merger Sub") into and
          with the Company and which amends the Purchase Contract Agreement
          dated as of March 31, 2001 among the Company and the Agent.

     (b)  Pursuant to Section 5.7(a)(i) of the Purchase Contract Agreement, the
          Settlement Rate from and after the Effective Time, the method of
          calculation thereof, and the facts requiring such adjustment and upon
          which such adjustment is based, are as follows: As of the Effective
          Time, the Merger Sub merged with and into the Company with the Company
          being the surviving corporation, and no shares of the Company's Common
          Stock remained publicly held. Section 5.6(c) of the Purchase Contract
          Agreement provides that the Merger constitutes a Reorganization Event
          whereupon the Settlement Rate will be adjusted to provide that each
          Holder of Securities will receive on the Purchase Contract Settlement
          Date, the kind and amount of securities, cash and other property
          receivable upon such Reorganization Event (without any interest
          thereon, and without any right to dividends or distribution thereon
          which have a record date that is prior to the Purchase Contract
          Settlement Date) by a holder of the number of shares of the Company's
          Common Stock issuable on account of each Purchase Contract as if the
          Purchase Contract Settlement Date had occurred immediately prior to
          such Reorganization Event and assuming such holder failed to exercise
          his rights of election as to the kind or amount of securities, cash
          and other property so receivable.

     (c)  Method of Calculation: (i) Upon Settlement of a Purchase Contract by a
          Holder at any time after midnight New York City time on May 31, 2002,
          the settling Holder thereof shall receive shares of Xcel Energy common
          stock instead of shares of common stock of the Company, at the Early
          Settlement Rate applicable on the Early Settlement Date or the
          adjusted Settlement Rate applicable on the Purchase Contract
          Settlement Date, as the case may be, as set forth in subsections
          (c)(ii) and (c)(iii) below;

          (ii) If a Holder elects Early Settlement under the terms of the
               Purchase Contract Agreement, the Early Settlement Rate shall be
               equal to the Early Settlement Rate that would have been
               applicable to Purchase Contracts if the Early Settlement Date had
               occurred immediately prior to the Effective Time of the Merger
               with respect to such Purchase Contracts (0.7590 of a share of
               common






               stock of the Company per Purchase Contract settled) multiplied by
               the exchange ratio in the Offer (0.5000 of a share of Xcel Energy
               common stock for each share of common stock of the Company) which
               equals 0.3795 of a share of common stock of Xcel Energy per
               Purchase Contract settled.

         (iii) If a Holder settles his Purchase Contract on the Purchase
               Contract Settlement Date, the Settlement Rate shall be equal to
               the Settlement Rate that would have been applicable to Purchase
               Contracts if the Purchase Contract Settlement Date had occurred
               immediately prior to the Effective Time of the Merger (0.9259 of
               a share of common stock of the Company per Purchase Contract
               settled) multiplied by the exchange ratio in the Offer (0.5000 of
               a share of Xcel Energy common stock for each share of common
               stock of the Company) which equals 0.4630 of a share of common
               stock of Xcel Energy per Purchase Contract settled;

         subject to any further adjustments to the Early Settlement Rate and the
         Settlement Rate under Article V of the Purchase Contract Agreement
         prior to settlement. Pursuant to the Purchase Contract Agreement, in
         the case of Cash Settlement, or through the application of Proceeds
         from related Treasury Securities, the Cash Settlement Rate will also be
         determined based on the adjusted Settlement Rate or Early Settlement
         Rate as applicable to the Xcel Energy Common Stock.

     (d)  The Company is not in default in the performance of any covenant or
          condition under the Purchase Contract Agreement, any of the
          Securities, or the Pledge Agreement. Capitalized terms used and not
          otherwise defined herein shall have the meanings ascribed to such
          terms in the Supplemental Agreement and the Purchase Contract
          Agreement.

                            [SIGNATURE PAGE FOLLOWS]








         IN WITNESS WHEREOF, the undersigned has duly executed this Officer's
Certificate as of this 6th day of June, 2002.



                                       NRG ENERGY, INC.



                                       By:  /s/  C. Adam Carte
                                            ------------------------------------
                                            C. Adam Carte
                                            Vice President & Treasurer