<PAGE>
                                                                    Exhibit 4.20


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



                        PINNACLE WEST CAPITAL CORPORATION

                                       TO

                              THE BANK OF NEW YORK

                                     TRUSTEE

                          Second Supplemental Indenture

                          Dated as of November 1, 2003

                                       To

                                    Indenture

                          Dated as of December 1, 2000

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

                       Floating Rate Senior Notes due 2005



                          -----------------------------
<PAGE>
      SECOND SUPPLEMENTAL INDENTURE, dated as of November 1, 2003, between
Pinnacle West Capital Corporation, a corporation duly organized and existing
under the laws of the State of Arizona (herein called the "Company"), having its
principal office at 400 North Fifth Street, Phoenix, Arizona 85004, and The Bank
of New York, a New York banking corporation, as Trustee (herein called the
"Trustee") under the Indenture dated as of December 1, 2000 between the Company
and the Trustee (the "Indenture").

                             RECITALS OF THE COMPANY

      The Company has executed and delivered the Indenture to the Trustee to
provide for the issuance from time to time of its unsecured debentures, notes or
other evidences of indebtedness (the "Securities"), said Securities to be issued
in one or more series as in the Indenture provided.

      The Company has executed and delivered to the Trustee one indenture
supplemental to the Indenture (the "First Supplemental Indenture") dated as of
March 15, 2001.

      Pursuant to the terms of the Indenture, the Company desires to provide for
the establishment of a new series of its Securities to be known as its Floating
Rate Senior Notes due 2005 (herein called the "Notes due 2005"), the form and
substance of such Notes due 2005 and the terms, provisions, and conditions
thereof to be set forth as provided in the Indenture and this Second
Supplemental Indenture.

      All things necessary to make this Second Supplemental Indenture a valid
agreement of the Company, and to make the Notes due 2005, when executed by the
Company and authenticated and delivered by the Trustee, the valid and binding
obligations of the Company, have been done.

      NOW, THEREFORE, THIS SECOND SUPPLEMENTAL INDENTURE WITNESSETH:

      For and in consideration of the premises and the purchase of the Notes due
2005 by the holders thereof (the "Holders"), and for the purpose of setting
forth, as provided in the Indenture, the form and substance of the Notes due
2005 and the terms, provisions, and conditions thereof, it is mutually agreed,
for the equal and proportionate benefit of all Holders of the Notes due 2005, as
follows:

                                   ARTICLE ONE

                         GENERAL TERMS AND CONDITIONS OF
                               THE NOTES DUE 2005

      SECTION 101. There shall be and is hereby authorized a series of
Securities designated the "Floating Rate Senior Notes due 2005" limited in
aggregate principal amount to $165,000,000, except as mentioned below, which
amount shall be as set forth in any Company Order for the authentication and
delivery of the Notes due 2005. The Notes due 2005 shall mature and the
principal shall be due and payable together with all accrued and unpaid interest
thereon on November 1, 2005 (the "Maturity Date"), and shall be issued in the
form of registered
<PAGE>
notes without coupons. The Company may, without the consent of the Holders,
issue additional Notes due 2005 having the same ranking and the same interest
rate, maturity and additional terms as the Notes due 2005. Any additional notes
would, together with the Notes due 2005, constitute a single series of
Securities under the Indenture. Any reference herein to the limitation in
aggregate principal amount of the Notes due 2005 shall take account of any such
issuance and the limitation (originally $165,000,000) shall be adjusted
accordingly.

      SECTION 102. The following defined terms used herein shall, unless the
context otherwise requires, have the meanings specified below. Capitalized terms
used herein for which no definition is provided herein shall have the meanings
set forth in the Indenture.

      "Business Day" means any day other than a Saturday or a Sunday or a day on
which banking institutions in The City of New York are authorized or required by
law or executive order to remain closed or a day on which the Corporate Trust
Office of the Trustee is closed for business.

      "Calculation Agent" means The Bank of New York or its successor appointed
by the Company, acting as calculation agent.

      "Interest Determination Date" means the second London Business Day
immediately preceding the first day of the relevant Interest Period.

      "Interest Period" means the period commencing on an Interest Payment Date
(as defined below) for the Notes due 2005 (or commencing on the issue date for
the Notes due 2005, if no interest has been paid or duly made available for
payment since that date) and ending on the day before the next succeeding
Interest Payment Date for the Notes due 2005.

      "LIBOR" for any Interest Determination Date will be the London interbank
offered rate for deposits in U.S. dollars having an index maturity of three
months for a period commencing on the second London Business Day immediately
following such Interest Determination Date (the "Three Month Deposits") in
amounts of not less than $1,000,000, as such rate appears on Telerate Page 3750,
at approximately 11:00 a.m., London time, on such Interest Determination Date.

      "London Business Day" means a day on which dealings in deposits in U.S.
dollars are transacted, or with respect to any future date, are expected to be
transacted, in the London interbank market.

      "Telerate Page 3750" means the display designated on page "3750" on
Moneyline Telerate (or such other page as may replace the 3750 page on that
service or such other service or services as may be nominated by the British
Bankers' Association for the purpose of displaying London interbank offered
rates for U.S. dollar deposits).

      SECTION 103. The Notes due 2005 shall be issued in certificated form,
except that the Notes due 2005 shall be issued initially as a Global Security to
and registered in the name of Cede & Co., as nominee of The Depository Trust
Company, as Depositary therefor. Any Notes due 2005 to be issued or transferred
to, or to be held by, Cede & Co. (or any successor thereof) for such purpose
shall bear the depositary legend in substantially the form set forth at the top
of the

                                       2
<PAGE>
form of Note due 2005 in Article Two hereof (in lieu of that set forth in
Section 204 of the Indenture), unless otherwise agreed by the Company, such
agreement to be confirmed in writing to the Trustee. Such Global Security may be
exchanged in whole or in part for Notes due 2005 registered, and any transfer of
such Global Security in whole or in part may be registered, in the name or names
of Persons other than such Depositary or a nominee thereof only under the
circumstances set forth in Clause (2) of the last paragraph of Section 305 of
the Indenture, or such other circumstances in addition to or in lieu of those
set forth in Clause (2) of the last paragraph of Section 305 of the Indenture as
to which the Company shall agree, such agreement to be confirmed in writing to
the Trustee. Principal of, and premium, if any, and interest on the Notes due
2005 will be payable, the transfer of Notes due 2005 will be registrable and
Notes due 2005 will be exchangeable for Notes due 2005 bearing identical terms
and provisions, at the office or agency of the Company in the Borough of
Manhattan, The City and State of New York; PROVIDED, HOWEVER, that payment of
interest may be made at the option of the Company by check mailed to the
registered holder at such address as shall appear in the Security Register.

      SECTION 104. Each Note due 2005 will bear interest at a per annum rate
(the "Rate of Interest") determined by the Calculation Agent (as described
below) from November 12, 2003 or from the most recent Interest Payment Date to
which interest has been paid or duly provided for until the principal thereof is
paid or made available for payment and at the same per annum rate determined by
the Calculation Agent on any overdue principal and premium and on any overdue
installment of interest, payable on February 1, May 1, August 1 and November 1
of each year (each, an "Interest Payment Date"), commencing on February 1, 2004,
to the person in whose name such Note due 2005 or any Predecessor Security is
registered, at the close of business on the fifteenth calendar day preceding
each Interest Payment Date (each, a "Regular Record Date"). Any such interest
installment not punctually paid or duly provided for shall forthwith cease to be
payable to the registered Holders on such Regular Record Date, and shall instead
be paid to the person in whose name the Note due 2005 (or one or more
Predecessor Securities) is registered at the close of business on a Special
Record Date to be fixed by the Trustee for the payment of such Defaulted
Interest, notice whereof shall be given to the registered Holders of the Notes
due 2005 (or one or more Predecessor Securities) not less than ten days prior to
such Special Record Date, or may be paid at any time in any other lawful manner
not inconsistent with the requirements of any securities exchange on which the
Notes due 2005 may be listed, and upon such notice as may be required by such
exchange, all as more fully provided in the Indenture.

      The Notes due 2005 will bear interest for each Interest Period at a per
annum rate determined by the Calculation Agent. The per annum interest rate will
be equal to LIBOR on the relevant Interest Determination Date plus 0.80%;
PROVIDED, HOWEVER, that in certain circumstances described below, the interest
rate will be determined by the Calculation Agent in an alternative manner
without reference to LIBOR. Promptly upon such determination, the Calculation
Agent will notify the Trustee of the interest rate for the new Interest Period.
The interest rate determined by the Calculation Agent, absent manifest error,
shall be binding and conclusive upon the beneficial owners and Holders of the
Notes due 2005, the Company and the Trustee.

      If the following circumstances exist on any Interest Determination Date,
the Calculation Agent shall determine the interest rate for the Notes due 2005
as follows:


                                       3
<PAGE>
            (1) In the event LIBOR cannot be determined from the Moneyline
      Telerate service as described herein as of approximately 11:00 a.m. London
      time on such Interest Determination Date, the Calculation Agent shall
      request the principal London offices of each of four major banks in the
      London interbank market selected by the Calculation Agent (after
      consultation with the Company) to provide a quotation of the rate (the
      "Rate Quotation") at which Three Month Deposits in amounts of not less
      than $1,000,000 are offered by it to prime banks in the London interbank
      market, at approximately 11:00 a.m. London time on such Interest
      Determination Date, that is representative of single transactions at such
      time (the "Representative Amounts"). If at least two Rate Quotations are
      provided, the interest rate will be the arithmetic mean of the Rate
      Quotations obtained by the Calculation Agent, plus 0.80%.

            (2) In the event LIBOR cannot be determined from the Moneyline
      Telerate service as described herein and fewer than two Rate Quotations
      are available as provided in (1) above, the interest rate will be the
      arithmetic mean of the rates quoted at approximately 11:00 a.m. New York
      City time on such Interest Determination Date, by three major banks in New
      York City, selected by the Calculation Agent (after consultation with the
      Company), for loans in Representative Amounts in U.S. dollars to leading
      European banks, having an index maturity of three months for a period
      commencing on the second London Business Day immediately following such
      Interest Determination Date, plus 0.80% PROVIDED, HOWEVER, that if fewer
      than three banks selected by the Calculation Agent are quoting such rates,
      the interest rate for the applicable Interest Period will be the same as
      the interest rate in effect for the immediately preceding Interest Period.

      Upon the request of a Holder of the Notes due 2005, the Calculation Agent
will provide to such Holder the interest rate in effect on the date of such
request and, if determined, the interest rate for the next Interest Period.

      Interest on the Notes due 2005 will be calculated on the basis of the
actual number of days for which interest is payable in the relevant Interest
Period, divided by 360. All dollar amounts resulting from such calculations will
be rounded, if necessary, to the nearest cent with one-half cent rounded upward.
In the event that any date on which interest is payable on the Notes due 2005 is
not a Business Day, then payment of interest payable on such date will be made
on the next succeeding day which is a Business Day (and without any interest or
other payment in respect of any such delay), in each case with the same force
and effect as if made on such date. If the Maturity Date of the Notes due 2005
or any redemption date falls on a day that is not a Business Day, the payment of
principal and interest (to the extent payable with respect to the principal
amount being redeemed if on a redemption date) will be made on the next
succeeding Business Day, and no interest on such payment shall accrue for the
period from and after the maturity date or such redemption date.

      SECTION 105. The Company may not redeem the Notes due 2005 prior to
November 1, 2004. The Company may redeem the Notes due 2005, in whole, on not
less than 30 days' nor more than 60 days' notice, beginning on November 1, 2004
and on each Interest Payment Date thereafter, prior to the Maturity Date of the
Notes due 2005, at a redemption price equal to 100% of

                                       4
<PAGE>
the principal amount plus accrued and unpaid interest thereon to the date of
redemption (the "Redemption Price").

      The Company will mail notice of the redemption, first-class mail postage
prepaid, to each Holder of Notes due 2005 to be redeemed at the Holder's address
in the Securities Register. Notice to the Holders will be given at least 30 but
not more than 60 days before the Redemption Date. Notes due 2005 to be redeemed
become due on the Redemption Date, and interest will cease to accrue on those
Notes due 2005 on the Redemption Date.

      The Company agrees that so long as any of the Notes due 2005 remain
outstanding, there shall at all times be a calculation agent for the Notes due
2005. If the Calculation Agent is unable or unwilling to continue to act as the
Calculation Agent or fails duly to establish the rate of interest for any
Interest Period, the Company shall appoint another leading commercial or
investment bank engaged in the London interbank market to act as such in its
place. In accordance with the agreement between the Company and the Calculation
Agent, the Calculation Agent may not resign its duties without a successor
calculation agent having been appointed as aforesaid.

      SECTION 106. The Notes due 2005 shall be defeasible pursuant to Section
1302 or 1303 of the Indenture.

                                   ARTICLE TWO

                             FORM OF NOTES DUE 2005

      SECTION 201. The Notes due 2005 and the Trustee's certificate of
authentication to be endorsed thereon are to be substantially in the following
forms:

Form of Face of Security:

      UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF
THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION ("DTC"), TO PINNACLE WEST
CAPITAL CORPORATION OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE, OR
PAYMENT, AND ANY CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR
IN SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND
ANY PAYMENT IS MADE TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN
AUTHORIZED REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE, OR OTHER USE HEREOF FOR
VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED
OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.


                                       5
<PAGE>
                        PINNACLE WEST CAPITAL CORPORATION

                       Floating Rate Senior Note due 2005

No. _________                                           $165,000,000
                                                        CUSIP No. ______________

      Pinnacle West Capital Corporation, a corporation duly organized and
existing under the laws of Arizona (herein called the "Company" which term
includes any successor person under the Indenture hereinafter referred to), for
value received, hereby promises to pay to Cede & Co., as nominee of The
Depository Trust Company, or registered assigns, the principal sum of One
Hundred Sixty-Five Million Dollars on November 1, 2005 (the "Maturity Date"),
and to pay interest at the rate set forth below on the outstanding principal
amount hereof from time to time from and including November 12, 2003 or from the
most recent Interest Payment Date (as defined below) to which interest has been
paid or duly provided for, quarterly in arrears on February 1, May 1, August 1
and November 1 in each year, commencing February 1, 2004, and on the Maturity
Date (each, an "Interest Payment Date"), until the principal hereof is paid or
made available for payment and at the same per annum rate set forth below on any
overdue principal and premium and on any overdue installment of interest. The
interest so payable, and punctually paid or duly provided for, on any Interest
Payment Date shall, as provided herein, be paid to the person in whose name this
Note (or one or more predecessor Notes) is registered at the close of business
on the fifteenth calendar day preceding each Interest Payment Date, (each a
"Regular Record Date"); PROVIDED, HOWEVER, that interest payable on the Maturity
Date, or any redemption date, shall be payable to the person to whom the
principal amount of this Note is payable. Any interest payable on any Interest
Payment Date other than the Maturity Date and not so punctually paid or duly
provided for shall forthwith cease to be payable to the person in whose name
this Note is registered at the close of business on such Regular Record Date and
shall instead be payable to the person in whose name this Note (or one or more
predecessor Notes) is registered at the close of business on a special record
date for the payment of such interest to be fixed by the Trustee hereinafter
referred to, notice whereof shall be given to the registered holder of this Note
(or one or more predecessor Notes) not less than ten days prior to such special
record date, or may be paid at any time in any other lawful manner not
inconsistent with the requirements of any securities exchange on which this Note
may be listed and upon such notice as may be required by such exchange, as more
fully provided in the Indenture. Principal of this Note shall be payable against
surrender hereof at the corporate trust office of the Trustee or at such other
office or agency of the Company as may be designated by it for such purpose in
the Borough of Manhattan, The City of New York.

      "Business Day" means any day other than a Saturday or a Sunday or a day on
which banking institutions in The City of New York are authorized or required by
law or executive order to remain closed or a day on which the corporate trust
office of the Trustee is closed for business.

      "Calculation Agent" means The Bank of New York or its successor appointed
by the Company, acting as calculation agent.

      "Interest Determination Date" means the second London Business Day
immediately

                                       6
<PAGE>
preceding the first day of the relevant Interest Period.

      "Interest Period" means the period commencing on an Interest Payment Date
for this Note (or commencing on the issue date for this Note, if no interest has
been paid or duly made available for payment since that date) and ending on the
day before the next succeeding Interest Payment Date for this Note.

      "LIBOR" for any Interest Determination Date will be the London interbank
offered rate for deposits in U.S. dollars having an index maturity of three
months for a period commencing on the second London Business Day immediately
following such Interest Determination Date (the "Three Month Deposits") in
amounts of not less than $1,000,000, as such rate appears on Telerate Page 3750,
at approximately 11:00 a.m., London time, on such Interest Determination Date.

      "London Business Day" means a day on which dealings in deposits in U.S.
dollars are transacted, or with respect to any future date, are expected to be
transacted, in the London interbank market.

      "Telerate Page 3750" means the display designated on page "3750" on
Moneyline Telerate (or such other page as may replace the 3750 page on that
service or such other service or services as may be nominated by the British
Bankers' Association for the purpose of displaying London interbank offered
rates for U.S. dollar deposits).

      Payment of the principal of and any interest on this Note will be made at
the corporate trust office of the Trustee or at such other office or agency of
the Company as may be designated by it for such purpose in the Borough of
Manhattan, The City of New York, in such coin or currency of the United States
of America as at the time of payment is legal tender for payment of public and
private debts; PROVIDED, HOWEVER, that, at the option of the Company payment of
interest may be made by check mailed to the address of the person entitled
thereto as such address shall appear in the register for the Notes.

      If any Interest Payment Date falls on a day that is not a Business Day,
the Interest Payment Date will be the next succeeding Business Day (without any
interest or other payment in respect of such delay). If the maturity date of the
Notes or any redemption date falls on a day that is not a Business Day, the
payment of principal and interest (to the extent payable with respect to the
principal amount being redeemed if on a redemption date) will be made on the
next succeeding Business Day, and no interest on such payment shall accrue for
the period from and after the maturity date or such redemption date.

      Reference is hereby made to the further provisions of this Note set forth
on the reverse hereof, which further provisions shall for all purposes have the
same effect as if set forth at this place.

      Unless the certificate of authentication hereon has been executed by the
Trustee referred to on the reverse hereof by manual signature, this Note shall
not be entitled to any benefit under the Indenture or be valid or obligatory for
any purpose.


                                       7
<PAGE>
      IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed under its corporate seal.

                                        PINNACLE WEST CAPITAL CORPORATION


                                        By
                                           -------------------------------------
                                                Vice President

Attest:


---------------------------------------------
             Associate Secretary

Form of Reverse of Security.

      This Note is one of a duly authorized issue of securities of the Company
(herein called the "Notes"), issued and to be issued in one or more series under
an Indenture, dated as of December 1, 2000, as amended and supplemented from
time to time (herein called the "Indenture", which term shall have the meaning
assigned to it in such instrument), between the Company and The Bank of New
York, as Trustee (herein called the "Trustee", which term includes any successor
trustee under the Indenture), and reference is hereby made to the Indenture for
a statement of the respective rights, limitations of rights, duties and
immunities thereunder of the Company, the Trustee and the holders of the Notes
and of the terms upon which the Notes are, and are to be, authenticated and
delivered. This Note is one of the series designated on the face hereof, limited
in aggregate principal amount to $165,000,000, subject to increase as provided
in Section 101 of the Second Supplemental Indenture, dated as of November 1,
2003, providing for the Notes.

      The Notes are not redeemable prior to November 1, 2004. The Notes will be
redeemable at the Company's option in whole, on not less than 30 days' nor more
than 60 days' notice, beginning on November 1, 2004 and on each Interest Payment
Date thereafter, prior to maturity of the Notes, at a redemption price equal to
100% of the principal amount thereof plus accrued and unpaid interest thereon to
the date of redemption.

      If notice has been given as provided in the Indenture and funds for the
redemption of Notes shall have been made available on the redemption date
referred to in such notice, the Notes will cease to bear interest on the date
fixed for such redemption specified in such notice and the only right of the
holders of the Notes will be to receive payment of the redemption price.


                                       8
<PAGE>
      The Company will mail notice of the redemption, first-class mail postage
prepaid, to each holder of Notes at the holder's address in the register for the
Notes. Notice to the holders will be given at least 30 but not more than 60 days
before the redemption date. Notes to be redeemed become due on the redemption
date, and interest will cease to accrue on the Notes on the redemption date.

      The Notes will not be subject to any sinking fund.

      The Notes will bear interest for each Interest Period at a per annum rate
determined by the Calculation Agent as described below (the "Rate of Interest").
The per annum interest rate will be equal to LIBOR on the relevant Interest
Determination Date plus 0.80%; PROVIDED, HOWEVER, that in certain circumstances
described below, the interest rate will be determined by the Calculation Agent
in an alternative manner without reference to LIBOR. Promptly upon such
determination, the Calculation Agent will notify the Trustee of the interest
rate for the new Interest Period. The interest rate determined by the
Calculation Agent, absent manifest error, shall be binding and conclusive upon
the beneficial owners and holders of the Notes, the Company and the Trustee.

      If the following circumstances exist on any Interest Determination Date,
the Calculation Agent shall determine the interest rate for the Notes as
follows:

            (1) In the event LIBOR cannot be determined from the Moneyline
      Telerate service as described herein as of approximately 11:00 a.m. London
      time on such Interest Determination Date, the Calculation Agent shall
      request the principal London offices of each of four major banks in the
      London interbank market selected by the Calculation Agent (after
      consultation with the Company) to provide a quotation of the rate (the
      "Rate Quotation") at which Three Month Deposits in amounts of not less
      than $1,000,000 are offered by it to prime banks in the London interbank
      market, at approximately 11:00 a.m. London time on such Interest
      Determination Date, that is representative of single transactions at such
      time (the "Representative Amounts"). If at least two Rate Quotations are
      provided, the interest rate will be the arithmetic mean of the Rate
      Quotations obtained by the Calculation Agent, plus 0.80%.

            (2) In the event LIBOR cannot be determined from the Moneyline
      Telerate service as described herein and fewer than two Rate Quotations
      are available as provided in (1) above, the interest rate will be the
      arithmetic mean of the rates quoted at approximately 11:00 a.m. New York
      City time on such Interest Determination Date, by three major banks in New
      York City, selected by the Calculation Agent (after consultation with the
      Company), for loans in Representative Amounts in U.S. dollars to leading
      European banks, having an index maturity of three months for a period
      commencing on the second London Business Day immediately following such
      Interest Determination Date, plus 0.80% PROVIDED, HOWEVER, that if fewer
      than three banks selected by the Calculation Agent are quoting such rates,
      the interest rate for the applicable Interest Period will be the same as
      the interest rate in effect for the immediately preceding Interest Period.


                                       9
<PAGE>
      Upon the request of a holder of the Notes, the Calculation Agent will
provide to such holder the interest rate in effect on the date of such request
and, if determined, the interest rate for the next Interest Period.

      No liability shall (in the absence of gross negligence, willful misconduct
or bad faith) attach to the Calculation Agent in connection with the exercise or
non-exercise by it of its powers, duties and discretions.

      The Indenture contains provisions for defeasance at any time of the entire
indebtedness of this Note or certain restrictive covenants and events of default
with respect to this Note, in each case upon compliance with certain conditions
set forth in the Indenture.

      If an event of default with respect to the Notes shall occur and be
continuing, the principal of the Notes may be declared due and payable in the
manner and with the effect provided in the Indenture.

      The Indenture permits, with certain exceptions as therein provided, the
amendment thereof and the modification of the rights and obligations of the
Company and the rights of the holders of the Notes to be affected under the
Indenture at any time by the Company and the Trustee without the consent of such
Holders in certain limited circumstances or with the consent of the Holders of
66 2/3% in principal amount of the securities at the time outstanding of each
series to be affected. The Indenture also contains provisions permitting the
holders of specified percentages in principal amount of the securities of each
series at the time outstanding, on behalf of the holders of all securities of
such series, to waive compliance by the Company with certain provisions of the
Indenture and certain past defaults under the Indenture and their consequences.
Any such consent or waiver by the holder of this Note shall be conclusive and
binding upon such holder and upon all future holders of this Note and of any
Note issued upon the registration of transfer hereof or in exchange herefor or
in lieu hereof, whether or not notation of such consent or waiver is made upon
this Note.

      As provided in and subject to the provisions of the Indenture, the holder
of this Note shall not have the right to institute any proceeding with respect
to the Indenture or for the appointment of a receiver or trustee or for any
other remedy thereunder, unless such holder shall have previously given the
Trustee written notice of a continuing event of default with respect to the
Notes, the holders of not less than 25% in principal amount of the Notes at the
time outstanding shall have made written request to the Trustee to institute
proceedings in respect of such event of default as Trustee and offered the
Trustee reasonable indemnity, and the Trustee shall not have received from the
holders of a majority in principal amount of Notes at the time outstanding a
direction inconsistent with such request, and shall have failed to institute any
such proceeding, for 60 days after receipt of such notice, request and offer of
indemnity. The foregoing shall not apply to any suit instituted by the holder of
this Note for the enforcement of any payment of principal hereof or any premium
or interest hereon on or after the respective due dates expressed herein.

      No reference herein to the Indenture and no provision of this Note or of
the Indenture shall alter or impair the obligation of the Company, which is
absolute and unconditional, to pay

                                       10
<PAGE>
the principal of and any premium and interest on this Note at the times, place
and rate, and in the coin or currency, herein prescribed.

      As provided in the Indenture and subject to certain limitations therein
set forth, the transfer of this Note is registrable in the register of the
Notes, upon surrender of this Note for registration of transfer at the office or
agency of the Company in any place where the principal of and any premium and
interest on this Note are payable, duly endorsed by, or accompanied by a written
instrument of transfer in form satisfactory to the Company and the registrar of
the Notes duly executed by the holder hereof or his attorney duly authorized in
writing, and thereupon one or more new Notes and of like tenor, of authorized
denominations and for the same aggregate principal amount, will be issued to the
designated transferee or transferees.

      The Notes are issuable only in registered form without coupons in
denominations of $1,000 and any integral multiple thereof. As provided in the
Indenture and subject to certain limitations therein set forth, Notes are
exchangeable for a like aggregate principal amount of Notes and of like tenor of
a different authorized denomination, as requested by the holder surrendering the
same.

      No service charge shall be made for any such registration of transfer or
exchange, but the Company may require payment of a sum sufficient to cover any
tax or other governmental charge payable in connection therewith.

      Prior to due presentment of this Note for registration of transfer, the
Company, the Trustee and any agent of the Company or the Trustee may treat the
person in whose name this Note is registered as the owner hereof for all
purposes, whether or not this Note be overdue, and neither the Company, the
Trustee nor any such agent shall be affected by notice to the contrary.

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

      This Note shall be governed by and construed in accordance with the law of
the State of New York, without regard to conflicts of laws principles thereof.


                                       11
<PAGE>
Form of Trustee's Certificate of Authentication.

                          CERTIFICATE OF AUTHENTICATION

      This is one of the Notes of the series designated therein referred to in
the within-mentioned Indenture.

Dated: _____________________              THE BANK OF NEW YORK
                                          AS TRUSTEE


                                          By
                                               ---------------------------------
                                                     AUTHORIZED SIGNATORY


                                  ARTICLE THREE

                        ORIGINAL ISSUE OF NOTES DUE 2005

      SECTION 301. Notes due 2005 in the aggregate principal amount of
$165,000,000 (subject to increase as provided in Section 101) may, upon
execution of this Second Supplemental Indenture, or from time to time
thereafter, be executed by the Company and delivered to the Trustee for
authentication, and the Trustee shall thereupon authenticate and deliver said
Notes due 2005 in accordance with a Company Order delivered to the Trustee by
the Company, without any further action by the Company.

                                  ARTICLE FOUR

                           PAYING AGENT AND REGISTRAR

      SECTION 401. The Bank of New York will be the Paying Agent and Security
Registrar for the Notes due 2005.

                                  ARTICLE FIVE

                                SUNDRY PROVISIONS

      SECTION 501. Except as otherwise expressly provided in this Second
Supplemental Indenture or in the form of Notes due 2005 or otherwise clearly
required by the context hereof or thereof, all terms used herein or in said form
of Notes due 2005 that are defined in the Indenture shall have the several
meanings respectively assigned to them thereby.

      SECTION 502. The Indenture, as heretofore supplemented and amended, and as
supplemented by this Second Supplemental Indenture, is in all respects ratified
and confirmed, and this Second Supplemental Indenture shall be deemed part of
the Indenture in the manner and to the extent herein and therein provided.


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<PAGE>
      SECTION 503. The Trustee hereby accepts the trusts herein declared,
provided, created, supplemented, or amended and agrees to perform the same upon
the terms and conditions herein and in the Indenture, as heretofore supplemented
and amended, set forth and upon the following terms and conditions:

      The Trustee shall not be responsible in any manner whatsoever for or in
respect of the validity or sufficiency of this Second Supplemental Indenture or
for or in respect of the recitals contained herein, all of which recitals are
made by the Company solely. In general, each and every term and condition
contained in Article Six of the Indenture shall apply to and form a part of this
Second Supplemental Indenture with the same force and effect as if the same were
herein set forth in full with such omissions, variations, and insertions, if
any, as may be appropriate to make the same conform to the provisions of this
Second Supplemental Indenture.

      This instrument 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.

      IN WITNESS WHEREOF, the parties hereto have caused this Second
Supplemental Indenture to be duly executed, and their respective corporate seals
to be hereunto affixed and attested, all as of the day and year first above
written.

                                            PINNACLE WEST CAPITAL CORPORATION

Attest:

        /s/ Betsy A. Pregulman
--------------------------------------
            Betsy A. Pregulman
            Associate Secretary

                                            By:  /s/ Barbara M. Gomez
                                                --------------------------------
                                                        Barbara M. Gomez
                                                        Treasurer


                                            THE BANK OF NEW YORK, as Trustee

Attest:

        /s/ Barbara Bevelaqua
--------------------------------------
            Barbara Bevelaqua
            Vice President

                                            By:  /s/ Van K. Brown
                                                --------------------------------
                                                        Van K. Brown
                                                        Vice President


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<PAGE>
STATE OF ARIZONA       )
                       )  ss.:
COUNTY OF MARICOPA     )

      On the 10th day of November, 2003, before me personally came Barbara M.
Gomez, to me known, who, being by me duly sworn, did depose and say that she is
the Treasurer of Pinnacle West Capital Corporation, one of the corporations
described in and which executed the foregoing instrument; that she knows the
seal of said corporation; that the seal affixed to said instrument is such
corporate seal; that it was so affixed by authority of the Board of Directors of
said corporation; and that she signed her name thereto by like authority.


                                                  /s/ Linda K. Redman
                                                --------------------------------
                                                         Notary Public

My Commission Expires:


February 8, 2007
----------------------------


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

      On the 10th day of November, 2003, before me personally came Van K. Brown,
to me known, who, being by me duly sworn, did depose and say that he is a Vice
President of The Bank of New York, one of the corporations described in and
which executed the foregoing 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 authority of the Board of Directors of said
corporation; and that he signed his name thereto by like authority.


                                                  /s/ Robert Hirsch
                                                --------------------------------
                                                         Notary Public

My Commission Expires:


July 1, 2006
----------------------------


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