AMENDMENT NO. 1 TO 364-DAY CREDIT AGREEMENT

THIS AMENDMENT NO. 1 TO 364-DAY CREDIT AGREEMENT (this “Amendment”) is made as of July 31, 2017, by and among PINNACLE WEST CAPITAL CORPORATION (the “Borrower”), the lenders listed on the signature pages hereof (the “Lenders”), and THE BANK OF TOKYO-MITSUBISHI UFJ, LTD., as Agent (the “Agent”), under that certain 364-Day Credit Agreement, dated as of August 31, 2016, by and among the Borrower, the lenders from time to time parties thereto and the Agent (as amended, restated, supplemented or otherwise modified from time to time, the “Credit Agreement”). Capitalized terms used but not otherwise defined herein shall have the meaning given to them in the Credit Agreement.

WHEREAS, the Borrower, the Lenders and the Agent are parties to the Credit Agreement;

WHEREAS, the Borrower has requested that the Agent and the Lenders amend the Credit Agreement on the terms and conditions set forth herein; and

WHEREAS, the Borrower, the Agent and the Lenders have agreed to amend the Credit Agreement on the terms and conditions set forth herein.

NOW, THEREFORE, in consideration of the premises set forth above, the terms and conditions contained herein, and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereto have agreed to the following:

“Capital Lease Obligations” means, subject to Section 1.03, as to any Person, the obligations of such Person to pay rent or other amounts under a lease of (or other agreement conveying the right to use) real and/or personal property, which obligations are required to be classified and accounted for as a capital lease or a finance lease on the balance sheet of such Person under GAAP and, for the purposes

of this Agreement, the amount of such obligations shall be the capitalized amount thereof, determined in accordance with GAAP.

“Indebtedness” means as to any Person at any date (without duplication): (a) indebtedness created, issued, incurred or assumed by such Person for borrowed money or evidenced by bonds, debentures, notes or similar instruments; (b) all obligations of such Person to pay the deferred purchase price of property or services, excluding, however, trade accounts payable (other than for borrowed money) arising in, and accrued expenses incurred in, the ordinary course of business of such Person so long as such trade accounts payable are paid within 180 days (unless subject to a good faith dispute) of the date incurred; (c) all Indebtedness secured by a Lien on any asset of such Person, to the extent such Indebtedness has been assumed by, or is a recourse obligation of, such Person; (d) all Guarantees by such Person; (e) all Capital Lease Obligations of such Person; and (f) the amount of all reimbursement obligations of such Person (whether contingent or otherwise) in respect of letters of credit, bankers’ acceptances, surety or other bonds and similar instruments in support of Indebtedness; provided that Indebtedness, in accordance with Section 1.03, shall exclude any obligation or liability arising from the application or interpretation of ASC Topic 840 or 842 or any related, similar or successor pronouncement, guideline, publication or rule, or which is otherwise excluded in accordance with Section 1.03.

“Termination Date” means the earlier of (a) July 30, 2018 and (b) the date of termination in whole of the Commitments pursuant to Section 2.05 or Section 6.01.

(c)    Section 1.03 of the Credit Agreement is hereby amended and restated in its entirety as follows:

Unless otherwise specified herein, and subject to the provision below, all accounting terms used herein shall be interpreted, all accounting determinations hereunder shall be made, and all financial statements required to be delivered hereunder shall be prepared, in accordance with generally accepted accounting principles as in effect from time to time, applied on a basis consistent (except for changes concurred in by the Borrower’s independent public accountants) with the most recent audited Consolidated financial statements of the Borrower delivered to the Agent (“GAAP”). If at any time any change in GAAP or in the interpretation thereof would affect the computation of any financial ratio or requirement set forth in any Loan Document, and either the Borrower or the Required Lenders shall so request, the Agent, the Lenders and the Borrower shall negotiate in good faith to amend such ratio or requirement to preserve the original intent thereof in light of such change in GAAP or in the interpretation thereof (subject to the approval of the Required Lenders); provided that, unless and until so amended, such ratio or requirement shall continue to be computed in accordance with GAAP prior to such change therein. Notwithstanding the foregoing, (a) for purposes of all financial or covenant calculations made under this Agreement and for purposes of defining and

calculating Capital Lease Obligations, Indebtedness and Consolidated Indebtedness hereunder for such purposes, all leases or other agreements of any Person deemed to be a lease or other obligation under GAAP (as in effect from time to time) (whether such lease or other agreement is existing as of the date hereof or hereafter entered into) that would not be characterized as (i) a Capital Lease Obligation, (ii) Indebtedness or (iii) Consolidated Indebtedness, in each case, under this Agreement based on GAAP as in effect as of December 31, 2015, will not be deemed to be (i) a Capital Lease Obligation, (ii) Indebtedness or (iii) Consolidated Indebtedness, respectively, as a result of any change in GAAP, or the interpretation or application thereof required or approved by such Person’s independent certified public accountants, occurring or coming into or taking effect after December 31, 2015, including ASC Topic 840 or 842 or any related, similar or successor pronouncement, guidance, publication or rule and (b) all terms of an accounting or financial nature used herein shall be construed, and all computations of amounts and ratios referred to herein shall be made (i) without giving effect to any election under Accounting Standards Codification 825-10-25 (or any other Accounting Standards Codification or Financial Accounting Standard having a similar result or effect) to value any Indebtedness or other liabilities of any Person at “fair value”, as defined therein and (ii) without giving effect to any treatment of Indebtedness in respect of convertible debt instruments under Accounting Standards Codification 470-20 (or any other Accounting Standards Codification or Financial Accounting Standard having a similar result or effect) to value any such Indebtedness in a reduced or bifurcated manner as described therein, and such Indebtedness shall at all times be valued at the full stated principal amount thereof.

(d)    Section 8.18 of the Credit Agreement is hereby amended (i) to replace the term “write-down and conversion powers” now appearing in the lead-in paragraph and clause (b)(iii) thereof with the following: “Write-Down and Conversion Powers”, and (ii) to replace the term “Bail-in Action” now appearing in clause (b) thereof with the following: “Bail-In Action”.

(e)    Schedule 1.01 of the Credit Agreement is hereby amended (i) to replace each occurrence of the term “$37,500,000” now appearing therein with the following: “$62,500,000”, and (ii) to replace the term “$75,000,000” now appearing therein with the following, “$125,000,000”.