Exhibit 99.1

 FORM OF CERTIFICATION PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002
                                (WILLIAM J. POST)

     I, William J. Post, the Chairman of the Board and Chief Executive Officer
of Pinnacle West Capital Corporation ("Pinnacle West"), certify, to the best of
my knowledge, that: (a) the attached Quarterly Report on Form 10-Q of Pinnacle
West for the quarterly period ended September 30, 2002 (the "September 2002 Form
10-Q") fully complies with the requirements of Section 13(a) or 15(d) of the
Securities Exchange Act of 1934 and (b) the information contained in the
September 2002 Form 10-Q Report fairly presents, in all material respects, the
financial condition and results of operations of Pinnacle West.


                                        William J. Post
                                        ----------------------------------------
                                        William J. Post
                                        Chairman of the Board and Chief
                                        Executive Officer

                                        Date: November 14, 2002