<Page>

                                                                    EXHIBIT 4.12









              -----------------------------------------------------


                               IDAHO POWER COMPANY

                                       TO

                              BANKERS TRUST COMPANY

                                       AND

                                  STANLEY BURG,

                              As Trustees under its
                           Mortgage and Deed of Trust
                             dated as of October 1,
                                      1937.

                                 ---------------

                     _______________ Supplemental Indenture
           providing among other things for Bonds of __________ Series
                          Dated as of __________, 200_

              -----------------------------------------------------

<Page>



                              TABLE OF CONTENTS(1)

                                                                            Page
Parties and Recitals....................................................
Granting Clause and Property Description................................

                    DESCRIPTION OF BONDS OF __________ SERIES

Section 1. General terms and redemption provisions......................
Section 2. Exchange and transfers of Bonds..............................
Section 3. Form of Bonds................................................
Section 4. Temporary Bonds..............................................

                       ISSUE OF BONDS OF __________ SERIES

Section 5. Issue of Bonds...............................................

                                    COVENANTS

Section 6. Application of Original Indenture............................
Section 7. Lawful ownership.............................................
Section 8. Annual certificate as to defaults............................

                                  THE TRUSTEES

Acceptance of trust.....................................................
Recitals deemed made by the Company.....................................

                            MISCELLANEOUS PROVISIONS

Meanings of terms.......................................................
Ratification and Confirmation...........................................
Counterparts............................................................
Testimonium.............................................................
Signatures and seals....................................................
Acknowledgments.........................................................
Affidavits..............................................................

--------
      (1)   This table of contents shall not have any bearing upon the
            interpretation of this Supplemental Indenture.


<Page>



                  SUPPLEMENTAL INDENTURE, dated as of the _____ day of
__________, 200_ made and entered into by and between IDAHO POWER COMPANY, a
corporation of the State of Idaho (successor by merger to Idaho Power Company, a
corporation of the State of Maine, hereinafter sometimes called the "Maine
Company"), whose address is 1221 West Idaho Street, Boise, Idaho 83702-5627
(hereinafter sometimes called the "Company"), party of the first part, and
BANKERS TRUST COMPANY, a corporation of the State of New York whose post office
address is Four Albany Street, New York, N.Y. 10006 (hereinafter sometimes
called the "Corporate Trustee"), and Stanley Burg (hereinafter sometimes called
the "Individual Trustee"), parties of the second part (the Corporate Trustee and
the Individual Trustee being hereinafter together sometimes called the
"Trustees"), as Trustees under the Mortgage and Deed of Trust dated as of
October 1, 1937 hereinafter referred to;

                  WHEREAS, the Maine Company has heretofore executed and
delivered to the Trustees its Mortgage and Deed of Trust (hereinafter sometimes
referred to as the "Original Indenture"), dated as of October 1, 1937, to secure
the payment both of the principal of and interest and premium, if any, on all
Bonds at any time issued and outstanding thereunder and to declare the terms and
conditions upon which Bonds are to be issued thereunder; and

                  WHEREAS, the Maine Company was merged into the Company on June
30, 1989; and

                  WHEREAS, in order to evidence the succession of the Company to
the Maine Company and the assumption by the Company of the covenants and
conditions of the Maine Company in the Bonds and in the Original Indenture, as
supplemented, contained, and to enable the Company to have and exercise the
powers and rights of the Maine Company under the Original Indenture, as
supplemented, in accordance with the terms thereof, the Company executed and
delivered to the Trustees a Twenty-eighth Supplemental Indenture, dated as of
June 30, 1989 (which supplemental indenture is hereinafter sometimes called the
"Twenty-eighth Supplemental Indenture"); and

                  WHEREAS, said Twenty-eighth Supplemental Indenture was
recorded in the records of the County of Elko, Nevada; the Counties of Baker,
Grant, Harney, Malheur, Union and Wallowa, Oregon; the Counties of Ada, Adams,
Bannock, Bear Lake, Bingham, Blaine, Boise, Bonneville, Butte, Camas, Canyon,
Caribou, Cassia, Clark, Elmore, Gem, Gooding, Idaho, Jefferson, Jerome, Lemhi,
Lincoln, Minidoka, Oneida, Owyhee, Payette, Power, Twin Falls, Valley and
Washington, Idaho; the Counties of Lincoln and Sweetwater, Wyoming; and with the
Secretary of State of Montana; and

                  WHEREAS, in accordance with the terms of the Original
Indenture the Maine Company or the Company has executed and delivered to the
Trustees the following supplemental indentures in addition to the Twenty-eighth
Supplemental Indenture:


<Page>

<Table>
<Caption>

         Designation                                                     Dated as of
         -----------                                                     -----------
<S>                                                                      <C>
First Supplemental Indenture............................................ July 1, 1939
Second Supplemental Indenture........................................... November 15, 1943
Third Supplemental Indenture............................................ February 1, 1947
Fourth Supplemental Indenture........................................... May 1, 1948
Fifth Supplemental Indenture............................................ November 1, 1949
Sixth Supplemental Indenture............................................ October 1, 1951
Seventh Supplemental Indenture.......................................... January 1, 1957
Eighth Supplemental Indenture........................................... July 15, 1957
Ninth Supplemental Indenture............................................ November 15, 1957
Tenth Supplemental Indenture............................................ April 1, 1958
Eleventh Supplemental Indenture......................................... October 15, 1958
Twelfth Supplemental Indenture.......................................... May 15, 1959
Thirteenth Supplemental Indenture....................................... November 15, 1960
Fourteenth Supplemental Indenture....................................... November 1, 1961
Fifteenth Supplemental Indenture........................................ September 15, 1964
Sixteenth Supplemental Indenture........................................ April 1, 1966
Seventeenth Supplemental Indenture...................................... October 1, 1966
Eighteenth Supplemental Indenture....................................... September 1, 1972
Nineteenth Supplemental Indenture....................................... January 15, 1974
Twentieth Supplemental Indenture........................................ August 1, 1974
Twenty-first Supplemental Indenture..................................... October 15, 1974
Twenty-second Supplemental Indenture.................................... November 15, 1976
Twenty-third Supplemental Indenture..................................... August 15, 1978
Twenty-fourth Supplemental Indenture.................................... September 1, 1979
Twenty-fifth Supplemental Indenture..................................... November 1, 1981
Twenty-sixth Supplemental Indenture..................................... May 1, 1982
Twenty-seventh Supplemental Indenture................................... May 1, 1986
Twenty-ninth Supplemental Indenture..................................... January 1, 1990
Thirtieth Supplemental Indenture........................................ January 1, 1991
Thirty-first Supplemental Indenture..................................... August 15, 1991
Thirty-second Supplemental Indenture.................................... March 15, 1992
Thirty-third Supplemental Indenture..................................... April 1, 1993
Thirty-fourth Supplemental Indenture.................................... December 1, 1993
Thirty-fifth Supplemental Indenture..................................... November 1, 2000
(2)
</Table>


--------
      (2)   Here will be inserted additional, executed supplemental indentures.

                                       -2-

<Page>


each of which is supplemental to the Original Indenture (the Original Indenture
and all indentures supplemental thereto together being hereinafter sometimes
referred to as the "Indenture"); and

                  WHEREAS, the Original Indenture and said Supplemental
Indentures (except said Fifteenth Supplemental Indenture) have each been
recorded in the records of the County of Elko, Nevada; the Counties of Baker,
Grant, Harney, Malheur, Union and Wallowa, Oregon; the Counties of Ada, Adams,
Bannock, Bear Lake, Bingham, Blaine, Boise, Bonneville, Butte, Camas, Canyon,
Caribou, Cassia, Clark, Elmore, Gem, Gooding, Idaho, Jefferson, Jerome, Lemhi,
Lincoln, Minidoka, Oneida, Owyhee, Payette, Power, Twin Falls, Valley and
Washington, Idaho; the Counties of Lincoln and Sweetwater, Wyoming; and with the
Secretary of State of Montana; and

                  WHEREAS, the Maine Company or the Company has heretofore
issued Bonds, under and in accordance with the terms of the Indenture in the
following series and aggregate principal amounts:

<Table>
<Caption>

                                                                        Principal                   Principal
                                                                         Amount                       Amount
Series                                                                   Issued                     Outstanding
------                                                                  --------                    -----------
<S>                                                                      <C>                            <C>
3-3/4% Series due 1967......................................             $18,000,000                    None
3-1/8% Series due 1973......................................              18,000,000                    None
2-3/4% Series due 1977......................................               5,000,000                    None
3% Series due 1978..........................................              10,000,000                    None
2-3/4% Series due 1979......................................              12,000,000                    None
3-1/4% Series due 1981......................................              15,000,000                    None
4-1/2% Series due 1987......................................              20,000,000                    None
4-3/4% Series due 1987......................................              15,000,000                    None
4% Series due April 1988....................................              10,000,000                    None
4-1/2% Series due October 1988..............................              15,000,000                    None
5% Series due 1989..........................................              15,000,000                    None
4-7/8% Series due 1990......................................              15,000,000                    None
4-1/2% Series due 1991......................................              10,000,000                    None
5-1/4% Series due 1996......................................              20,000,000                    None
6-1/8% Series due 1996......................................              30,000,000                    None
7-3/4% Series due 2002......................................              30,000,000                    None
8-3/8% Series due 2004......................................              35,000,000                    None
10% Series due 2004.........................................              50,000,000                    None
8-1/2% Series due 2006......................................              30,000,000                    None
9% Series due 2008..........................................              60,000,000                    None
</Table>


                                       -3-

<Page>

<Table>
<Caption>

                                                                        Principal                   Principal
                                                                         Amount                       Amount
Series                                                                   Issued                     Outstanding
------                                                                  --------                    -----------
<S>                                                                      <C>                            <C>
10-1/4% Series due 2003.....................................              62,000,000                    None
First Mortgage Bonds, 1984 Series...........................              10,100,000                    None
16.10% Series due 1991-1992.................................              50,000,000                    None
Pollution Control Series A..................................              49,800,000                    49,800,000
8.65% Series due 2000.......................................              80,000,000                    80,000,000
9.50% Series due 2021.......................................              75,000,000                    75,000,000
9.52% Series due 2031.......................................              25,000,000                    25,000,000
8% Series due 2004..........................................              50,000,000                    50,000,000
8 3/4% Series due 2027......................................              50,000,000                    50,000,000
Secured Medium-Term Notes, Series A.........................             190,000,000                   160,000,000
Secured Medium-Term Notes, Series B.........................             197,000,000                   197,000,000
Secured Medium-Term Notes, Series C.........................             200,000,000                   200,000,000
(3)
</Table>

which bonds are hereinafter sometimes called bonds of the First through
__________ Series; and

                  WHEREAS, the Company, in accordance with the provisions of the
Indenture and pursuant to appropriate resolutions of its Board of Directors, has
duly determined to make, execute and deliver to the Trustees this __________
Supplemental Indenture for the purposes herein provided, including the issuance
of a __________ Series of Bonds under the Indenture, in the aggregate principal
amount of up to __________ Million Dollars ($__________), to be designated as
"First Mortgage Bonds, _____% Series due __________" ["First Mortgage Bonds,
Secured Medium-Term Notes, Series _____"](4) (herein sometimes called the "Bonds
of __________ Series"); and


----------
      (3)   Here will be inserted additional outstanding series of bonds.

      (4)   Bracketed language will be inserted in lieu of words "First
            Mortgage Bonds, _____% Series due ___" in any supplemental indenture
            relating to the issuance of First Mortgage Bonds which are
            designated "Secured Medium-Term Notes, Series _____".



                  WHEREAS, it is also now desired, for the purpose of more
effectually carrying out the purposes of the Original Indenture, to confirm
specifically the subjection to the lien thereof and of the Indenture of the
certain property acquired by the Company in addition to the property

                                       -4-
<Page>

specifically described in the Original Indenture and in said First, Second,
Third, Fourth, Fifth, Sixth, Seventh, Ninth, Tenth, Eleventh, Twelfth,
Thirteenth, Fourteenth, Sixteenth, Seventeenth, Eighteenth, Nineteenth,
Twenty-first, Twenty-second, Twenty-third, Twenty-fourth, Twenty-fifth,
Twenty-sixth, Twenty-seventh, Twenty-eighth, Twenty-ninth, Thirtieth,
Thirty-first, Thirty-second, Thirty-third, Thirty-fourth and Thirty-fifth(5)
Supplemental Indentures; and

                  WHEREAS, all things necessary to make said Bonds of _________
Series, when duly authenticated by the Corporate Trustee and issued by the
Company, valid and legally binding obligations of the Company and to make the
Original Indenture, as heretofore supplemented and as supplemented hereby, a
valid and legally binding instrument for the security thereof, have been
performed, and the execution and delivery of this __________ Supplemental
Indenture and the issue of said Bonds as in this __________ Supplemental
Indenture provided have been in all respects duly authorized:

                  NOW, THEREFORE, THIS INDENTURE WITNESSETH:

                  That in consideration of the premises and of One Dollar to it
duly paid by the Trustees at or before the ensealing and delivery of these
presents, the receipt whereof is hereby acknowledged, and in order to secure the
payment both of the principal of and interest and premium, if any, on all Bonds
at any time issued and outstanding under the Indenture, according to their tenor
and effect, and the performance of all the provisions of the Indenture and of
said Bonds, the Company has duly executed and delivered to the Trustees this
__________ Supplemental Indenture and has granted, bargained, sold, released,
conveyed, assigned, transferred, mortgaged, pledged, set over and confirmed and
by these presents does grant, bargain, sell, release, convey, assign, transfer,
mortgage, pledge, set over and confirm unto Stanley Burg and (to the extent of
its legal capacity to hold the same for the purposes hereof) unto Bankers Trust
Company, as Trustees as aforesaid, and to their successor or successors in said
trust, and to them and their successors, heirs and assigns forever, all
property, whether real, personal or mixed (except any hereinafter expressly
excepted), and wheresoever situated, acquired since the date of said Original
Indenture by and now or hereafter owned by the Company including the following
described properties, rights and interests in property (in addition to all other
properties heretofore subjected to the lien of the Indenture and not heretofore
released from the lien thereof)--that is to say:(6)


----------
      (5)   Here will be inserted additional, executed supplemental indentures.

      (6)   Here will be inserted property descriptions.

                  All other property, whether real, personal or mixed (except
any hereinafter expressly excepted), and wheresoever situated, acquired since
the date of said Original Indenture by and now or hereafter owned by the
Company.

                                       -5-

<Page>

                  TOGETHER with all and singular the tenements, hereditaments
and appurtenances belonging or in any wise appertaining to the aforesaid
Property or any part thereof, with the reversion and reversions, remainder and
remainders, and (subject to the provisions of Section 57 of the Original
Indenture) the tolls, rents, revenues, issues, earnings, income, product and
profits thereof, and all the estate, right, title and interest and claim
whatsoever, at law as well as in equity, which the Company now has or may
hereafter acquire in and to the aforesaid property and franchises and every part
and parcel thereof.

                  It is not intended herein or hereby to include in or subject
to the lien of the Indenture, and the granting clauses hereof shall not be
deemed to apply to, (1) any revenues, earnings, rents, issues, income or profits
of the mortgaged and pledged property, or any bills, notes or accounts
receivable, contracts or choses in action, except to the extent permitted by law
in case a completed default specified in Section 65 of the Indenture shall have
occurred and be continuing and either or both of the Trustees, or a receiver or
trustee, shall have entered upon or taken possession of the mortgaged and
pledged property, or (2) in any case, unless specifically subjected to the lien
thereof, any bonds, notes, evidences of indebtedness, shares of stock, or other
securities or any cash (except cash deposited with the Corporate Trustee
pursuant to any provisions of the Indenture) or any goods, wares, merchandise,
equipment or apparatus manufactured or acquired for the purpose of sale or
resale in the usual course of business.

                  TO HAVE AND TO HOLD all such properties, real, personal and
mixed, granted, bargained, sold, released, conveyed, assigned, transferred,
mortgaged, pledged, set over or confirmed by the Company as aforesaid, or
intended so to be, unto the Individual Trustee and (to the extent of its legal
capacity to hold the same for the purposes hereof) unto the Corporate Trustee,
and their successors, heirs and assigns forever;

                  IN TRUST, NEVERTHELESS, for the same purposes and upon the
same terms, trusts and conditions and subject to and with the same provisions
and covenants as are set forth in the Original Indenture, as amended or modified
by said First, Second, Third, Fourth, Fifth, Sixth, Seventh, Eighth, Ninth,
Tenth, Eleventh, Twelfth, Thirteenth, Fourteenth, Fifteenth, Sixteenth,
Seventeenth, Eighteenth, Nineteenth, Twentieth, Twenty-first, Twenty-second,
Twenty-third, Twenty-fourth, Twenty-fifth, Twenty-sixth, Twenty-seventh,
Twenty-eighth, Twenty-ninth, Thirtieth, Thirty-first, Thirty-second,
Thirty-third, Thirty-fourth and Thirty-fifth Supplemental Indentures and this
_________(7) Supplemental Indenture.


--------
      (7)   Here will be inserted additional, executed supplemental indentures.

                  And it is hereby covenanted, declared and decreed by and
between the parties hereto, for the benefit of those who shall hold the Bonds
and interest coupons, or any of them, issued and to be issued under the
Indenture, as follows:

                                       -6-

<Page>

                                    ARTICLE I

                   DESCRIPTION OF BONDS OF __________ SERIES.

                  SECTION 1. The __________ Series of Bonds to be executed,
authenticated and delivered under and secured by the Indenture shall be Bonds of
__________ Series, designated as "First Mortgage Bonds, _____% Series due
__________" of the Company. The Bonds of __________ Series shall be executed,
authenticated and delivered in accordance with the provisions of, and shall in
all respects be subject to, all of the terms, conditions and covenants of the
Original Indenture, except insofar as the terms and provisions of the Original
Indenture have been or are amended or modified by said First through __________
Supplemental Indentures or by this __________ Supplemental Indenture. Bonds of
__________ Series shall mature on __________, and shall be issued as registered
Bonds without coupons in denominations of $1,000 and in any multiple thereof,
and shall bear interest, payable on __________ and __________ of each year, at
the rate of _____% per annum until the principal shall have become due and
payable, and, if default shall be made in the payment of said principal when due
and payable, at the rate of _____% per annum thereafter until the Company's
obligation with respect to payment of said principal shall have been discharged
as provided in the Indenture; provided, however, that if Bonds of __________
Series shall have been declared due and payable prior to their stated maturity
and such declaration shall have been annulled as provided in the Indenture, the
principal of such Bonds shall not be deemed to have been so declared due and
payable. The principal of and interest and premium, if any, on the Bonds of
__________ Series shall be payable at the office or agency of the Company in the
Borough of Manhattan, The City of New York, and, at the option of the Company,
interest on each said Bond may also be payable at the office of the Company in
Boise, Idaho, in such coin or currency of the United States of America as at the
time of payment shall be legal tender for public and private debts. The interest
on the Bonds of __________ Series, whether in temporary or definitive form,
shall be payable without presentation of such Bonds and (subject to the
provisions of this Section 1) only to or upon the written order of the
registered holders thereof.

                  Except as provided in the next succeeding sentence of this
Section 1, each Bond of __________ Series shall be dated the date of its
authentication and interest shall be payable on the principal represented
thereby from the __________ or __________, as the case may be, next preceding
the date thereof to which interest has been paid, unless the date thereof is a
__________ or __________ to which interest has been paid, in which case such
interest shall be payable from such date or unless such date is prior to
__________, in which case interest shall be payable from __________. Each Bond
of __________ Series authenticated between the record date for any interest
payment date and such interest payment date shall be dated the date of its
authentication, but interest shall be payable from such interest payment date;
provided, however, that if the Company shall default in the payment of the
interest due on such interest payment date, any Bond of __________

Series so authenticated shall bear interest from the __________ or __________,
as the case may be, next preceding the date of such Bond, to which interest
has been paid.

                                       -7-

<Page>

                  Interest on any Bond of __________ Series shall be paid to the
registered holder of such Bond of __________ Series, or, notwithstanding the
cancellation thereof, the Bond of __________ Series in exchange or substitution
for which such Bond shall have been issued, at the close of business on the
applicable record date; provided, however, that if the Company shall default in
the payment of the interest due on any interest payment date on the principal
represented by any Bond of __________ Series, such defaulted interest shall be
paid to the registered holder of such Bond (or any Bond or Bonds of __________
Series issued upon transfer or exchange thereof) on the date of payment of such
defaulted interest or, at the election of the Company, to the person in whose
name such Bond (or any Bond or Bonds of __________ Series issued upon transfer
or exchange thereof) is registered on a subsequent record date established by
notice given by mail by or on behalf of the Company to the holders of Bonds of
__________ Series not less than ten (10) days preceding such subsequent record
date. The term "record date" as used in this Section 1 shall mean, with respect
to any semi-annual interest payment date thereafter, the close of business on
__________ or __________, as the case may be, next preceding such interest
payment date or, in the case of defaulted interest, the close of business on any
subsequent record date established as provided above.

                  The Bonds of __________ Series, in definitive form, shall be,
at the option of the Company, fully engraved or shall be lithographed or printed
on steel engraved borders or shall be partially lithographed or printed and
partially engraved on steel engraved borders or shall be printed on safety paper
or shall be typewritten.

                  (8)[SECTION 1. The __________ Series of Bonds to be executed,
authenticated and delivered under and secured by the Indenture shall be Secured
Medium-Term Notes, Series _____, designated as "First Mortgage Bonds, Secured
Medium-Term Notes, Series _____ "of the Company. The Bonds of __________ Series
shall be executed, authenticated and delivered in accordance with the provisions
of, and shall in all respects be subject to, all of the terms, conditions and
covenants of the Original Indenture, except insofar as the terms and provisions
of the Original Indenture have been or are amended or modified by said First
through __________ Supplemental Indentures or by this __________ Supplemental
Indenture. Bonds of __________ Series shall be issued from time to time in an
aggregate principal amount not to exceed $__________, be issued as registered
Bonds without coupons in the denominations of $1,000 or in any multiple thereof;
each Bond of __________ Series shall mature on such date not less than
__________ nor more than __________ from date of issue, shall bear interest at
such rate or rates (which may be either fixed or variable) and have such other
terms and provisions not inconsistent with the Indenture as the Board of
Directors may determine in accordance with a resolution filed with the Corporate
Trustee and a written order referring to this __________ Supplemental Indenture;

                                       -8-

<Page>

the principal of and interest on each said Bond


--------
      (8)   These provisions will be inserted in lieu of Section 1 above in any
            supplemental indenture relating to the issuance of First Mortgage
            Bonds which are designated "Secured Medium-Term Notes, Series
            _____".

to be payable at the office or agency of the Company in the Borough of
Manhattan, The City of New York and, at the option of the Company, interest on
each said Bond may also be payable at the office of the Company in Boise, Idaho,
in such coin or currency of the United States of America as at the time of
payment is legal tender for public and private debts. Interest on Bonds of
__________ Series which bear interest at a fixed rate shall be payable
semiannually on __________ and __________ of each year and at maturity (each an
interest payment date). Interest on Bonds of __________ Series which bear
interest at a variable rate shall be payable on the dates (each an interest
payment date) set forth in a resolution filed with the Corporate Trustee
referring to this __________ Supplemental Indenture.

                  Notwithstanding the foregoing, so long as there is no existing
default in the payment of interest on the Bonds of __________ Series, all Bonds
of __________ Series authenticated by the Corporate Trustee after the Record
Date hereinafter specified for any interest payment date, and prior to such
interest payment date (unless the date of first authentication of Bonds of such
designated interest rate and maturity is after such Record Date), shall be dated
the date of authentication, but shall bear interest from such interest payment
date, and the person in whose name any Bond of __________ Series is registered
at the close of business on any Record Date with respect to any interest payment
date shall be entitled to receive the interest payable on such interest payment
date, notwithstanding the cancellation of such Bond of __________ Series, upon
any transfer or exchange thereof subsequent to the Record Date and on or prior
to such interest payment date. If the date of first authentication of the Bonds
of __________ Series of a designated interest rate and maturity is after such
Record Date and prior to the corresponding interest payment date, such Bonds
shall bear interest from the Original Interest Accrual Date but payment of
interest shall commence on the second interest payment date succeeding the
Original Interest Accrual Date. "Record Date" for Bonds of __________ Series
which bear interest at a fixed rate shall mean __________ for interest payable
__________ and __________ for interest payable __________, and for Bonds of
__________ Series which bear interest at a variable rate, the date 15 calendar
days prior to any interest payment date, provided that, interest payable on the
maturity date will be payable to the person to whom the principal thereof shall
be payable. "Original Interest Accrual Date" with respect to Bonds of __________
Series of a designated interest rate and maturity shall mean the date of first
authentication of Bonds of such designated interest rate and maturity unless a
written order filed with the Corporate Trustee on or before such date shall
specify another date from which interest shall accrue, in which case "Original
Interest Accrual Date" shall mean such other date specified in the written order
for Bonds of such designated interest rate and maturity.

                  The Bonds of __________ Series, in definitive form, shall be,
at the option of the Company, fully engraved or shall be lithographed or printed
on steel engraved borders or shall be partially lithographed or printed and
partially engraved on steel borders or shall be printed on safety paper or shall
be typewritten.]
                                       -9-

<Page>

                  The holders of the Bonds of __________ Series consent that the
Company may, but shall not be obligated to, fix a record date for the purpose of
determining the holders of Bonds of __________ Series entitled to consent to any
amendment, supplement or waiver. If a record date is


fixed, those persons who are holders at such record date (or their duly
designated proxies), and only those persons, shall be entitled to consent to
such amendment, supplement or waiver or to revoke any consent previously given,
whether or not such persons continue to be holders after such record date. No
such consent shall be valid or effective for more than 90 days after such record
date.

                 [HERE WILL BE INSERTED REDEMPTION PROVISIONS.]

                  SECTION 2. At the option of the registered holder, any Bonds
of __________ Series, upon surrender thereof for cancellation at the office or
agency of the Company in the Borough of Manhattan, The City of New York,
together with a written instrument of transfer (if so required by the Company or
by the Trustees) in form approved by the Company duly executed by the registered
holder or by his duly authorized attorney, shall be exchangeable for a like
aggregate principal amount and maturity of Bonds of __________ Series of other
authorized denominations. Bonds of __________ Series may bear such legends as
may be necessary to comply with any law or with any rules or regulations made
pursuant thereto or with the rules or regulations of any stock exchange or to
conform to usage with respect thereto.

                  Bonds of __________ Series shall be transferable at the office
or agency of the Company in the Borough of Manhattan, The City of New York.

                  Notwithstanding the foregoing provisions of this Section 2,
the Company shall not be required to make any transfers or exchanges of Bonds of
__________ Series for a period of fifteen (15) days next preceding any mailing
of notice of redemption, and the Company shall not be required to make transfers
or exchanges of the principal amount of any Bonds of __________ Series so called
or selected for redemption.

                  SECTION 3. The Bonds of __________ Series shall be
substantially of the tenor and purport recited in the Original Indenture, and
the form thereof shall be as established by resolution of the Board of Directors
or the Executive Committee of the Board of Directors of the Company, which
resolution may provide that any provisions of such form of Bond may appear on
the reverse of such form.

                  SECTION 4. Until Bonds of __________ Series in definitive form
are ready for delivery, the Company may execute, and upon its request in
writing, the Corporate Trustee shall authenticate and deliver, in lieu thereof,
Bonds of __________ Series in temporary form, as provided in Section 15 of the
Original Indenture.

                                      -10-

<Page>

                                   ARTICLE II

                      ISSUE OF BONDS OF __________ SERIES.

                  SECTION 5. The Bonds of __________ Series for the aggregate
principal amount of up to __________ Million Dollars ($___________) may be
executed by the Company and

delivered to the Corporate Trustee and shall be authenticated by the Corporate
Trustee and delivered to or upon the order or orders of the Company, evidenced
by a writing or writings signed by the Company by its President or a Vice
President and its Treasurer or an Assistant Treasurer, pursuant to and upon
compliance with the provisions of Article V, Article VI or Article VII of the
Indenture.

                                   ARTICLE III

                                   COVENANTS.

                  THE COMPANY HEREBY COVENANTS, WARRANTS AND AGREES:

                  SECTION 6. That all the terms, conditions, provisos, covenants
and provisions contained in the Indenture shall affect and apply to the property
hereinabove described and conveyed and to the estate, rights, obligations and
duties of the Company and Trustees and the beneficiaries of the trust with
respect to said property, and to the Trustees and their successors as trustees
of said property, in the same manner and with the same effect as if the said
property had been owned by the Company at the time of the execution of the
Original Indenture and had been specifically and at length described in and
conveyed to the Individual Trustee and (to the extent of its legal capacity to
hold the same for the purposes of the Indenture) the Corporate Trustee by the
Original Indenture as a part of the property therein stated to be conveyed.

                  SECTION 7. That it is lawfully seized and possessed of all of
the mortgaged and pledged property described in the granting clauses of the
Indenture, which has not heretofore been released from the lien thereof; that it
had or has, at the respective times of execution and delivery of the Original
Indenture, the First, Second, Third, Fourth, Fifth, Sixth, Seventh, Eighth,
Ninth, Tenth, Eleventh, Twelfth, Thirteenth, Fourteenth, Fifteenth, Sixteenth,
Seventeenth, Eighteenth, Nineteenth, Twentieth, Twenty-first (as corrected by
the Twenty-second), Twenty-second, Twenty-third, Twenty-fourth, Twenty-fifth,
Twenty-sixth, Twenty-seventh, Twenty-eighth, Twenty-ninth, Thirtieth,
Thirty-first, Thirty-second, Thirty-third, Thirty-fourth and Thirty-fifth
Supplemental Indentures, and this __________(9) Supplemental Indenture, good
right and lawful authority to mortgage and pledge the mortgaged and pledged
property described therein, as provided in and by the Indenture; and that such
mortgaged and pledged property is, at the actual

--------
      (9)   Here will be inserted additional, executed supplemental indentures.


                                      -11-

<Page>

date of the initial issue of the Bonds of __________ Series, free and clear of
any mortgage, lien, charge or encumbrance thereon or affecting the title thereto
(other than excepted encumbrances) prior to the lien of the Indenture, except as
set forth in the granting clauses of the Indenture.

                  SECTION 8. That it will deliver to the Corporate Trustee
annually, within ninety (90) days after the close of each fiscal year,
commencing with the fiscal year 200_, a certificate from the principal executive
officer, principal financial officer or principal accounting officer as to his
or her knowledge of the Company's compliance with all conditions and covenants
under the Indenture.

For purposes of this Section 8, such compliance shall be determined without
regard to any period of grace or requirement of notice provided under the
Indenture.

                                   ARTICLE IV

                                  THE TRUSTEES.

                  The Trustees hereby accept the trust hereby declared and
provided and agree to perform the same upon the terms and conditions in the
Original Indenture, as heretofore supplemented and as supplemented by this
__________ Supplemental Indenture, and in this __________ Supplemental Indenture
set forth, and upon the following terms and conditions:

                  The Trustees shall not be responsible in any manner whatsoever
for or in respect of the validity or sufficiency of this ____________
Supplemental Indenture or the due execution hereof by the Company or for or in
respect of the recitals contained herein, all of which recitals are made by the
Company only.

                                    ARTICLE V

                            MISCELLANEOUS PROVISIONS.

                  All terms contained in the __________ Supplemental Indenture
shall, for all purposes hereof, have the meanings given to such terms in Article
I of the Original Indenture, as amended by Article IV of the Second Supplemental
Indenture.

                  Except as hereby expressly amended and supplemented, the
Original Indenture heretofore amended and supplemented is in all respects
ratified and confirmed, and all the terms and provisions thereof shall be and
remain in full force and effect.

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


                                      -12-

<Page>



                  IN WITNESS WHEREOF, Idaho Power Company, party hereto of the
first part, caused its corporate name to be hereunto affixed and this instrument
to be signed and sealed by its President or a Vice President and its corporate
seal to be attested by its Secretary or an Assistant Secretary for and on its
behalf, and Bankers Trust Company, one of the parties hereto of the second part,
in token of its acceptance of the trust hereby created has caused its corporate
name to be hereunto affixed and this instrument to be signed and sealed by an
Assistant Vice President and its corporate seal to be attested by an Assistant
Vice President and Stanley Burg, one of the parties hereto of the second part,
has for all like purposes hereunto set his hand and affixed his seal, each on
the date hereinafter acknowledged, as of the day and year first above written.

                                                 IDAHO POWER COMPANY


                                                 By
                                                   -----------------------------

Attest:


-----------------------------



Executed, sealed and delivered by
    IDAHO POWER COMPANY
    in the presence of:


-----------------------------



-----------------------------


                                      -13-

<Page>



                                                 BANKERS TRUST COMPANY



                                                 By
                                                   -----------------------------


Attest:


-----------------------------





Executed, sealed and delivered by
    BANKERS TRUST COMPANY,
    in the presence of:


-----------------------------


-----------------------------



                                                     -------------------- [L.S.]
                                                        Stanley Burg

Executed, sealed and delivered by
    STANLEY BURG,
    in the presence of:


-----------------------------


-----------------------------


                                      -14-

<Page>



STATE OF IDAHO                      )
                                    ) ss.:
COUNTY OF ADA                       )


                  On the _____ day of __________ , in the year 200_, before me
personally came ____________________, to me known, who being by me duly sworn
did depose and say that he resides at _____________________________; that he is
the ___________________ of Idaho Power Company, one of the corporations
described in and which executed the above instrument; that he knows the seal of
said corporation; that the seal affixed to said instrument is such corporate
seal; that it was so affixed by order of the Board of Directors of said
corporation, and that he signed his name thereto by like order; the said
____________________, having personally appeared and known to me to be the
___________________ of said corporation that executed the instrument,
acknowledged to me that said corporation executed the same.

                  IN WITNESS WHEREOF, I have hereunto subscribed my name and
affixed my official seal the day and year in this certificate first above
written.



                                                 -------------------------------
                                                 Notary Public, State of Idaho


                                      -15-

<Page>



STATE OF NEW YORK                   )
                                    ) ss.:
COUNTY OF NEW YORK                  )


                  On the _____ day of __________ , in the year 200_, before me
personally came ____________________, to me known, who being by me duly sworn
did depose and say that he resides at _____________________________; that he is
an ___________________ of Bankers Trust Company, one of the corporations
described in and which executed the above instrument; that he knows the seal of
said corporation; that the seal affixed to said instrument is such corporate
seal; that it was so affixed by order of the Board of Directors of said
corporation, and that he signed his name thereto by like order; the said
____________________, having personally appeared and known to me to be an
___________________ of said corporation that executed the instrument,
acknowledged to me that said corporation executed the same.

                  IN WITNESS WHEREOF, I have hereunto subscribed my name and
affixed my official seal the day and year in this certificate first above
written.



                                     -------------------------------------------
                                     Notary Public, State of New York
                                     No. __________
                                     Qualified in __________ County
                                     Certificate filed in New York County
                                     Commission Expires __________




                                      -16-

<Page>



STATE OF NEW YORK                   )
                                    ) ss.:
COUNTY OF NEW YORK                  )


                  On the _____ day of __________, in the year 200_, before me,
_______________, a Notary Public in and for the State of New York in the County
of New York, personally appeared and came STANLEY BURG, to me known and known to
me to be the person described in and who executed the within and foregoing
instrument and whose name is subscribed thereto and acknowledged to me that he
executed the same.

                  IN WITNESS WHEREOF, I have hereunto subscribed my name and
affixed my official seal the day and year in this certificate first above
written.



                                     -------------------------------------------
                                     Notary Public, State of New York
                                     No. __________
                                     Qualified in __________ County
                                     Certificate filed in New York County
                                     Commission Expires __________


                                      -17-

<Page>



STATE OF IDAHO                      )
                                    ) ss.:
COUNTY OF ADA                       )


                  __________, being first duly sworn, upon oath, deposes and
says: that he is an officer, to wit, the __________ of Idaho Power Company, a
corporation, the mortgagor described in the foregoing indenture or mortgage, and
makes this affidavit on behalf of said Idaho Power Company; that said indenture
or mortgage is made in good faith without any design to hinder, delay or defraud
creditors, to secure the indebtedness mentioned to be thereby secured.




                                          ______________________________________



Subscribed and sworn to before me
this _____ day of __________, 200_.




------------------------------------
Notary Public, State of Idaho



                                      -18-

<Page>



STATE OF NEW YORK                   )
                                    ) ss.:
COUNTY OF NEW YORK                  )


                  __________, being first duly sworn, upon oath, deposes and
says: that he is an officer, to wit, an __________ of Bankers Trust Company, a
corporation, one of the mortgagees and trustees named in the foregoing indenture
or mortgage, and makes this affidavit on behalf of said Bankers Trust Company;
that said indenture or mortgage is made in good faith without any design to
hinder, delay or defraud creditors, to secure the indebtedness mentioned or
provided for therein.




                                           _____________________________________



Subscribed and sworn to before me
this _____ day of __________, 200_.




-------------------------------------
Notary Public, State of New York
No. __________
Qualified in __________ County
Certificate filed in New York County
Commission Expires __________


                                      -19-

<Page>


STATE OF NEW YORK                   )
                                    ) ss.:
COUNTY OF NEW YORK                  )


                  STANLEY BURG, being first duly sworn, upon oath, deposes and
says: that he is one of the mortgagees and trustees named in the foregoing
indenture or mortgage; that said indenture or mortgage is made in good faith
without any design to hinder, delay or defraud creditors, to secure the
indebtedness mentioned or provided for therein.


                                         _______________________________________
                                                     Stanley Burg


Subscribed and sworn to before me
this _____ day of __________, 200_.





-------------------------------------
Notary Public, State of New York
No. __________
Qualified in __________ County
Certificate filed in New York County
Commission Expires __________



                                      -20-