Document:

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                                                                  EXHIBIT 4.1(b)

Nevada Power Company
6226 W. Sahara Avenue
P.O. Box 230
Las Vegas, Nevada  89146

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                             NEVADA POWER COMPANY

                                      TO

                             THE BANK OF NEW YORK
                                    Trustee

                                  ----------

                         FIRST SUPPLEMENTAL INDENTURE

                            Dated as of May 1, 2001

                                  ----------

          Supplementing the General and Refunding Mortgage Indenture
                            Dated as of May 1, 2001

        THIS INSTRUMENT GRANTS A SECURITY INTEREST BY A PUBLIC UTILITY

          THIS INSTRUMENT CONTAINS AFTER-ACQUIRED PROPERTY PROVISIONS

This instrument is being filed pursuant to Nevada Revised Statutes Chapter 105

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         FIRST SUPPLEMENTAL INDENTURE, dated as of May 1, 2001, between NEVADA
POWER COMPANY, a corporation organized and existing under the laws of the State
of Nevada (herein called the "Company"), having its principal office at 6226 W.
Sahara Avenue, P.O. Box 230, Las Vegas, Nevada 89146, and THE BANK OF NEW YORK,
a banking corporation duly organized and existing under the laws of the State of
New York, as Trustee (herein called the "Trustee"), the office of the Trustee at
which on the date hereof its corporate trust business is principally
administered being 101 Barclay Street, New York, New York 10286.

                             RECITALS OF THE COMPANY

         WHEREAS, the Company has heretofore executed and delivered to the
Trustee a General and Refunding Mortgage Indenture dated as of May 1, 2001 (the
"Indenture") providing for the issuance by the Company from time to time of its
bonds, notes or other evidence of indebtedness to be issued in one or more
series (in the Indenture and herein called the "Securities") and to provide
security for the payment of the principal of and premium, if any, and interest;
if any, on the Securities; and

         WHEREAS, the Company, in the exercise of the power and authority
conferred upon and reserved to it under the provisions of the Indenture and
pursuant to appropriate resolutions of the Board of Directors, has duly
determined to make, execute and deliver to the Trustee this First Supplemental
Indenture to the Indenture as permitted by Sections 2.01, 3.01 and 14.01 of the
Indenture in order to establish the form or terms of, and to provide for the
creation and issuance of, the Initial Series of Securities under the Indenture
in an initial aggregate principal amount of $350,000,000 (such first series
being hereinafter and in the Indenture referred to as the "Initial Series"); and

         WHEREAS, all things necessary to make the Securities of the Initial
Series, when executed by the Company and authenticated and delivered by the
Trustee or any Authenticating Agent and issued upon the terms and subject to the
conditions hereinafter and in the Indenture set forth against payment therefor
the valid, binding and legal obligations of the Company and to make this First
Supplemental Indenture a valid, binding and legal agreement of the Company, have
been done;

         NOW, THEREFORE, THIS FIRST SUPPLEMENTAL INDENTURE WITNESSETH that, in
order to establish the terms of a series of Securities, and for and in
consideration of the premises and of the covenants contained in the Indenture
and in this First Supplemental Indenture and for other good and valuable
consideration the receipt and sufficiency of which are hereby acknowledged, it
is mutually covenanted and agreed as follows:
<PAGE>

                                   ARTICLE ONE

                        DEFINITIONS AND OTHER PROVISIONS
                             OF GENERAL APPLICATION

         Section 101. Definitions. Each capitalized term that is used herein and
                      -----------
is defined in the Indenture shall have the meaning specified in the Indenture
unless such term is otherwise defined herein.

                                   ARTICLE TWO

                       TITLE, FORM AND TERMS OF THE BONDS

         Section 201. Title of the Bonds. This First Supplemental Indenture
                      ------------------
hereby creates a series of Securities designated as the "8.25% General and
Refunding Mortgage Bonds, Series A, due June 1, 2011" of the Company
(collectively referred to herein as the "Bonds"). For purposes of the Indenture,
the Bonds shall constitute a single series of Securities and may be issued in an
unlimited principal aggregate amount, although the initial issuance of the Bonds
shall be in the principal amount of $350,000,000.

         Section 202. Form and Terms of the Bonds. The form and terms of the
                      ---------------------------
Bonds will be set forth in an Officer's Certificate delivered by the Company to
the Trustee pursuant to the authority granted by this First Supplemental
Indenture in accordance with Sections 2.01 and 3.01 of the Indenture.

         Section 203. Treatment of Proceeds of Title Insurance Policy. Any
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moneys received by the Trustee as proceeds of any title insurance policy on
Mortgaged Property of the Company shall be subject to and treated in accordance
with the provisions of Section 6.07(b) of the Indenture (other than the last
paragraph thereof).

                                  ARTICLE THREE

                            MISCELLANEOUS PROVISIONS

         The Trustee makes no undertaking or representations in respect of, and
shall not be responsible in any manner whatsoever for and in respect of, the
validity or sufficiency of this First Supplemental Indenture or the proper
authorization or the due execution hereof by the Company or for or in respect of
the recitals and statements contained herein, all of which recitals and
statements are made solely by the Company.

         Except as expressly amended and supplemented hereby, the Indenture
shall continue in full force and effect in accordance with the provisions
thereof and the Indenture is in all respects hereby ratified and confirmed. This
First Supplemental Indenture and all of its provisions shall be deemed a part of
the Indenture in the manner and to the extent herein and therein provided.
<PAGE>

         This First Supplemental Indenture 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 or any
successor to such statute).

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

                                                                  EXHIBIT 4.1(c)

                             NEVADA POWER COMPANY

                             OFFICER'S CERTIFICATE

         I, the undersigned officer of Nevada Power Company (the "Company"), do
hereby certify that I am an Authorized Officer of the Company as such term is
defined in the Indenture (as defined herein). I am delivering this certificate
pursuant to the authority granted in the Board Resolutions of the Company dated
May 22, 2001, and Sections 1.04, 2.01, 3.01 and 4.01(a) of the General and
Refunding Mortgage Indenture dated as of May 1, 2001 (the "Mortgage Indenture"),
as supplemented by a First Supplemental Indenture dated as of May 1, 2001 (the
"Supplemental Indenture"; and collectively with the Mortgage Indenture, the
"Indenture"), between the Company and The Bank of New York, as Trustee (the
"Trustee"). Terms used herein and not otherwise defined herein shall have the
meanings assigned to them in the Indenture unless the context clearly requires
otherwise. Based upon the foregoing, I hereby certify on behalf of the Company
as follows:

         1.    The terms and conditions of the Securities described in this
Officer's Certificate are as follows (the lettered subdivisions set forth in
this Paragraph 1 corresponding to the lettered subdivisions of Section 3.01 of
the Mortgage Indenture):

         (a)   The Securities of the first series to be issued under the
         Indenture shall be designated "8.25% General and Refunding Mortgage
         Bonds, Series A, due June 1, 2011" (the "Series A Bonds").

         (b)   There shall be no limit upon the aggregate principal amount of
         the Series A Bonds that may be authenticated and delivered under the
         Indenture. The Series A Bonds shall be initially authenticated and
         delivered in the aggregate principal amount of $350,000,000.

         (c)   Interest on the Series A Bonds shall be payable to the Persons in
         whose names such Securities are registered at the close of business on
         the Regular Record Date for such interest, except as otherwise
         expressly provided in the form of such Securities attached hereto as
         Exhibit A.
         ---------

         (d)   The Series A Bonds shall mature and the principal thereof shall
         be due and payable together with all accrued and unpaid interest
         thereon on June 1, 2011.

         (e)   The Series A Bonds shall bear interest at the rate of 8.25% per
         annum. Interest shall accrue on the Series A Bonds from May 24, 2001,
         or the most recent date to which interest has been paid or duly
         provided for. The Interest Payment Dates for the Series A Bonds shall
         be June 1 and December 1 in each year commencing December 1, 2001, and
         the Regular Record Dates with respect to the Interest Payment Dates for
         the Series A Bonds shall be May 17 and November 16 in each year,
         respectively (whether or not a Business Day).

         (f)   The Corporate Trust Office of The Bank of New York in New York,
         New York shall be the place at which (i) the principal of, premium and
         interest on, the Series A
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         Bonds shall be payable, (ii) registration of transfer of the Series A
         Bonds may be effected, (iii) exchanges of the Series A Bonds may be
         effected and (iv) notices and demands to or upon the Company in respect
         of the Series A Bonds and the Indenture may be served; and The Bank of
         New York shall be the Security Registrar for the Series A Bonds;
         provided, however, that the Company reserves the right to change, by
         --------  -------
         one or more Officer's Certificates, any such place or the Security
         Registrar; and provided, further, that the Company reserves the right
         to designate, by one or more Officer's Certificates, its principal
         office in Las Vegas, Nevada as any such place or itself as the Security
         Registrar; provided, however, that there shall be only a single
         Security Registrar for the Series A Bonds.

         (g)   The Series A Bonds shall be redeemable, at the option of the
         Company, at any time or from time to time, in whole or in part, at a
         price equal to 100% of the principal amount of the Series A Bonds to be
         redeemed plus accrued and unpaid interest to the Redemption Date
         (subject to the right of Holders of record on a Regular Record Date
         occurring prior to such Redemption Date to receive interest paid on the
         applicable Interest Payment Date ) plus the applicable make-whole
         premium (the "Make-Whole Premium").

               The amount of the Make-Whole Premium with respect to the Series A
         Bonds (or portion thereof) to be redeemed will be equal to the excess,
         if any, of:

               (i)    the sum of the present values, calculated as of the
         Redemption Date, of:

                      (A)   each interest payment that, but for such redemption,
                      would have been payable on the Series A Bonds (or portion
                      thereof) being redeemed on each Interest Payment Date
                      occurring after the Redemption Date (excluding any accrued
                      and unpaid interest for the period prior to the Redemption
                      Date); and

                      (B)   the principal amount that, but for such redemption,
                      would have been payable at the Stated Maturity of the
                      Series A Bonds (or portion thereof) being redeemed,

               over

               (ii)   the principal amount of the Series A Bonds (or portion
         thereof) being redeemed.

               The present values of each interest and principal payment
         referred to in clause (i) above will be determined in accordance with
         generally accepted principles of financial analysis. Such present
         values will be calculated by discounting the amount of each payment of
         interest or principal from the date that each such payment would have
         been payable, but for such redemption, to the Redemption Date at a
         discount rate equal to the Treasury Yield (as defined below) plus 30
         basis points.

               The Make-Whole Premium will be calculated by Credit Suisse First
         Boston Corporation or, if such firm is unwilling or unable to make such
         calculation, by an

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         independent investment banking institution of national standing
         appointed by the Company (in any such case, an "Independent Investment
         Banker"). The Trustee shall have no responsibility for the calculation
         of the Make-Whole Premium and may conclusively presume the correctness
         of such calculation.

               For purposes of determining the Make-Whole Premium, "Treasury
         Yield" means a rate of interest per annum equal to the weekly average
         yield to maturity of United States Treasury Notes that have a constant
         maturity that corresponds to the remaining term to maturity of the
         Series A Bonds, calculated to the nearest 1/12 of a year (the
         "Remaining Term"). The Treasury Yield will be determined as of the
         third business day immediately preceding the applicable Redemption
         Date.

               The weekly average yields of United States Treasury Notes will be
         determined by reference to the most recent statistical release
         published by the Federal Reserve Bank of New York and designated
         "H.15(519) Selected Interest Rates" or any successor release (the "H.15
         Statistical Release"). If the H.15 Statistical Release sets forth a
         weekly average yield for United States Treasury Notes having a constant
         maturity that is the same as the Remaining Term, then the Treasury
         Yield will be equal to such weekly average yield. In all other cases,
         the Treasury Yield will be calculated by interpolation, on a
         straight-line basis, between the weekly average yields on the United
         States Treasury Notes that have a constant maturity closest to and
         greater than the Remaining Term and the United States Treasury Notes
         that have a constant maturity closest to and less than the Remaining
         Term (in each case as set forth in the H.15 Statistical Release). Any
         weekly average yields so calculated by interpolation will be rounded to
         the nearest 1/100th of 1%, with any figure of 1/200 of 1% or above
         being rounded upward. If weekly average yields for United States
         Treasury Notes are not available in the H.15 Statistical Release or
         otherwise, then the Treasury Yield will be calculated by interpolation
         of comparable rates selected by the Independent Investment Banker.

               If less than all of the Series A Bonds are to be redeemed, the
         Security Registrar will select the Series A Bonds to be redeemed by
         such method as the Security Registrar shall deem fair and appropriate.
         The Trustee may select for redemption Series A Bonds and portions of
         Series A Bonds in amounts of $1,000 or whole multiples of $1,000;
         subject to clause (i) of this Paragraph 1 (as to minimum
         denominations).

         (h)   Not applicable.

         (i)   The Series A Bonds are issuable only in denominations of $250,000
         and integral multiples of $1000 in excess thereof.

         (j)   Not applicable.

         (k)   Not applicable.

         (l)   Not applicable.

         (m)   Not applicable.

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         (n)   Not applicable.

         (o)   Pursuant to the terms of a registration rights agreement with one
         or more of the initial purchasers of the Series A Bonds (a
         "Registration Rights Agreement"), the Company has agreed to file an
         exchange offer registration statement to exchange the Series A Bonds
         for substantially identical Securities registered under the Securities
         Act of 1933, as amended (the "Securities Act") as evidence of the same
         underlying indebtedness. Unless otherwise specified by the Company in a
         supplement to this Officer's Certificate, the Securities so registered
         and offered and issued in exchange shall be additional Series A Bonds.
         The Company has also agreed to file a shelf registration statement to
         cover resales of the Series A Bonds, as initially issued and sold,
         under certain circumstances. If the Company fails to satisfy those
         obligations, the Company has agreed to pay liquidated damages to the
         holders of the Series A Bonds under certain circumstances. The terms
         relating to the exchange of the Series A Bonds are set forth in the
         Registration Rights Agreement attached hereto as Exhibit B.
                                                          ---------

         (p)   Not applicable.

         (q)   Certificates representing Series A Bonds offered and sold in
         reliance on Rule 144A (and only such Series A Bonds) shall be in the
         form of a permanent certificate in global form (a "Global Certificate")
         registered in the name of Cede & Co., as nominee for The Depository
         Trust Company (the "Depositary"), to be delivered to the Depositary or
         its custodian, by or on behalf of the Company. The Global Certificate
         shall not be transferable or exchangeable, nor shall any purported
         transfer be registered, except as follows:

               (i)    the Global Certificate may be transferred in whole, and
               appropriate registration of transfer effected, if such transfer
               is by such nominee to the Depositary, or by the Depositary to
               another nominee thereof, or by any nominee of the Depositary to
               any other nominee thereof, or by the Depositary or any nominee
               thereof to any successor securities depositary or any nominee
               thereof; and

               (ii)   the Global Certificate may be exchanged for Series A
               Bonds in the form of definitive certificates, registered in the
               respective names of the beneficial owners thereof, and thereafter
               shall be transferable without restriction, if:

                      (A)   the Depositary, or any successor securities
                      depositary, shall have notified the Company and the
                      Trustee that (i) it is unwilling or unable to continue to
                      act as securities depositary with respect to the Series A
                      Bonds, (ii) has ceased to be qualified to act as such, or
                      (iii) has ceased to be a clearing agency registered under
                      the Exchange Act, and the Trustee shall not have been
                                        ---
                      notified by the Company within ninety (90) days of the
                      identity of a successor securities depositary with respect
                      to such Securities;

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<PAGE>

                      (B)   the Company shall have delivered to the Trustee a
                      Company Order to the effect that the Company has elected
                      to terminate the book-entry system; or

                      (C)   an Event of Default shall have occurred and be
                      continuing.

               Unless and until definitive, fully registered certificates shall
         have been issued to beneficial owners as provided in subclause (ii) of
         this clause (g) of Paragraph 1 hereof:

                      (a)   the provisions of this clause (q) shall be in full
               force and effect;

                      (b)   the Company and the Trustee and any agent of either
               shall be entitled to deal with the Depositary for all purposes of
               the indenture and such Series A Bonds (including payment of
               principal of, and premium and interest thereon, the giving of
               notice and receiving approvals, votes or consents thereunder) as
               the Holder of such Securities and the sole holder of the Global
               Certificate and shall have no obligation to the beneficial owners
               of such Securities;

                      (c)   to the extent that the provisions of clause (q) of
               paragraph 1 conflicts with any other provisions of the Indenture
               or the Series A Bonds, the provisions of this clause (q) of
               Paragraph 1 shall control; and

                      (d)   the rights of such beneficial owners shall be
               exercised only through the Depositary and shall be limited to
               those established by law and agreements between such beneficial
               owners or of any agent member of, or direct or indirect
               participants in, the Depositary and the Depositary or the
               depositary participants. The Depositary will make book-entry
               transfers among depositary participants and receive and transmit
               payments of principal, premium and interest, if any, to such
               depositary participants.

               Notwithstanding the foregoing, with respect to any Global
         Certificate, nothing contained herein or in the Indenture shall prevent
         the Company, the Trustee or any agent of the Company or the Trustee,
         from giving effect to any written certification, proxy or other
         authorization furnished by the Depositary (or its nominee), as a
         Holder, with respect to such Global Certificate or impair, as between
         such Depositary and the related beneficial owner, the operation of
         customary practices governing the exercise of rights of the Depositary
         (or its nominee) as Holder of such global certificate. Except for the
         Global Certificate, any and all of the Series A Bonds shall be in the
         form of a non-global, definitive physical certificate.

         (r)   Not applicable.

         (s)   The Series A Bonds have not been registered under the Securities
         Act and may not be offered, sold or otherwise transferred in the
         absence of such registration or an applicable exemption therefrom. No
         service charge shall be made for the registration of transfer or
         exchange of the Series A Bonds, or any Tranche thereof; provided,
         however,

                                       5
<PAGE>

         that the Company may require payment of a sum sufficient to cover any
         tax or other governmental charge payable in connection with the
         exchange or transfer.

         (t)   For purposes of the Series A Bonds, "Business Day" shall mean any
         day, other than Saturday or Sunday, on which commercial banks and
         foreign exchange markets are open for business, including dealings in
         deposits in U.S. dollars, in New York.

         (u)   Notwithstanding the provisions of Section 9.01 of the Indenture,
         no Series A Bond shall be deemed to have been paid, and the
         indebtedness of the Company in respect thereof deemed to have been
         satisfied and discharged as contemplated therein, unless the Company
         shall have delivered to the Trustee either:

               (i)    an opinion of counsel in the United States reasonably
               acceptable to the Trustee confirming that (A) the Company has
               received from, or there has been published by, the Internal
               Revenue Service a ruling or (B) since the date of the Indenture,
               there has been a change in the applicable federal income tax law,
               in either case to the effect that, and based thereon such opinion
               of counsel shall confirm that, the Holders of the outstanding
               Bonds will not recognize income, gain or loss for federal income
               tax purposes as a result of such defeasance and will be subject
               to federal income tax on the same amounts, in the same manner and
               at the same times as would have been the case if such defeasance
               had not occurred; or

               (ii)   (A) an instrument wherein the Company, notwithstanding the
               satisfaction and discharge of its Indebtedness in respect of the
               Bonds, shall assume the obligation (which shall be absolute and
               unconditional) to irrevocably deposit with the Trustee such
               additional sums of money, if any, or additional Government
               Obligations, if any, or any combination thereof, at such time or
               times, as shall be necessary, together with the money and/or
               Government Obligations theretofore so deposited, to pay when due
               the principal of and premium, if any, and interest due and to
               become due on such bonds or portions thereof; provided, however,
               that such instrument may state that the obligation of the Company
               to make additional deposits as aforesaid shall be subject to the
               delivery to the Company by the Trustee of a notice asserting the
               deficiency accompanied by an opinion of an independent public
               accountant of nationally recognized standing showing the
               calculation thereof; and (B) an opinion of tax counsel in the
               United States reasonably acceptable to the Trustee to the effect
               that the Holders of the outstanding Bonds will not recognize
               income, gain or loss for federal income tax purposes as a result
               of such defeasance and will be subject to federal income tax on
               the same amounts, in the same manner and at the same times as
               would have been the case if such defeasance had not occurred.

         The Series A Bonds shall have such other terms and provisions as are
provided in the form thereof attached hereto as Exhibit A, and shall be issued
                                                ---------
in substantially such form.

         2.    All conditions precedent provided for in the Mortgage Indenture
and the Indenture (including any covenants compliance with which constitutes a
condition precedent)

                                       6
<PAGE>

relating to the execution and delivery of the Supplemental Indenture and the
authentication and delivery of the Series A Bonds have been complied with.

         3.    The undersigned has read all of the covenants and conditions
contained in the Indenture, and the definitions in the Indenture relating
thereto, relating to the issuance of the Series A Bonds and in respect of
compliance with which this certificate is made.

         4.    The statements contained in this certificate are based upon the
familiarity of the undersigned with the Indenture, the documents accompanying
this certificate, and upon discussions by the undersigned with officers and
employees of the Company familiar with the matters set forth herein.

         5.    In the opinion of the undersigned, he has made such examination
or investigation as is necessary to enable him to express an informed opinion as
to whether or not such covenants and conditions have been complied with.

                                       7
<PAGE>

         IN WITNESS WHEREOF, the undersigned has executed this Officer's
Certificate on this 24th day of May, 2001.

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

Acknowledged and Received on
May __, 2001

THE BANK OF NEW YORK,
as Trustee

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

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