8-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

| Date of report (Date of earliest event reported): | August 28, 2025 | | --- | --- || Commission File<br>Number | Exact Name of Registrant as Specified in<br>Charter; State or Other Jurisdiction of Incorporation; Address of Principal Executive Officers, and Zip Code; and<br>Registrant's telephone Number, Including Area Code) | | | IRS Employer<br>Identification No. | | --- | --- | --- | --- | --- | | 1-8962 | PINNACLE WEST CAPITAL CORPORATION | | | 86-0512431 | | | (an Arizona corporation) | | | | | | 400 North Fifth Street, P.O. Box 53999 | | | | | | Phoenix | Arizona | 85072-3999 | | | | (602) | 250-1000 | | |

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR §230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2).

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

Item 1.01    Entry into a Material Definitive Agreement

On August 28, 2025, Pinnacle West Capital Corporation (the “Company”) entered into an amendment (the “Amendment”) to the forward sale agreements (the “Forward Sale Agreements”), dated as of February 28, 2024 and February 29, 2024, respectively, between the Company and Wells Fargo Bank, National Association. The Amendment provides for a December 31, 2026 settlement date for the Share Forward Transactions (as defined in the Amendment), subject to the terms of the Forward Sale Agreements.

The above summary of the Amendment does not purport to be complete and is qualified in its entirety by the Amendment, a copy of which is attached to this Current Report on Form 8-K as Exhibit 10.1 and incorporated by reference herein.

Item 9.01    Financial Statements and Exhibits.

(d)    Exhibits

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Document

Exhibit 10.1

Ladies and Gentlemen:

This letter agreement (this “Amendment”) amends each of the Confirmation dated as of February 28, 2024 (“Confirmation 1”) and the Confirmation dated as of February 29, 2024 (“Confirmation 2”, together with Confirmation 1, the “Confirmations”) in respect of the Share Forward Transactions between Wells Fargo Bank, National Association (“Dealer”) and Pinnacle West Capital Corporation (“Counterparty”), as amended and supplemented from time to time. Any capitalized term used but not defined herein shall have the meaning assigned thereto in the Confirmations.

1.Amendment.

(a)“September 4, 2025” under the term Maturity Date shall be replaced with “December 31, 2026”.

(b)Schedule I of the Confirmations is hereby amended by replacing it with the following:

[Redacted]

2.As of the date of this Amendment, Party B hereby repeats (i) the representations, warranties and agreements contained in the Confirmations under the headers “Representations and Agreements of Party B”, “Additional Representations, Warranties and Agreements of Party B”, “Additional Mutual Representation and Warranty” and “Covenant of Party B” and (ii) the representation in Section 3(a)(iii) of the 2002 ISDA Master Agreement.

3.No Additional Amendments or Waivers. Except as amended hereby, all the terms of the Transactions and provisions in the Confirmations shall remain and continue in full force and effect and

are hereby confirmed in all respects.

4.Counterparts. This Amendment may be signed in any number of counterparts, each of which shall be an original, with the same effect as if all of the signatures thereto and hereto were upon the same instrument.

5.Governing Law; Jurisdiction. THIS AMENDMENT AND ANY CLAIM, CONTROVERSY OR DISPUTE ARISING UNDER OR RELATED TO THIS AMENDMENT SHALL BE GOVERNED BY THE LAWS OF THE STATE OF NEW YORK. THE PARTIES HERETO IRREVOCABLY SUBMIT TO THE EXCLUSIVE JURISDICTION OF THE COURTS OF THE STATE OF NEW YORK AND THE UNITED STATES COURT FOR THE SOUTHERN DISTRICT OF NEW YORK IN CONNECTION WITH ALL MATTERS RELATING HERETO AND WAIVE ANY OBJECT TO THE LAYING OF VENUE IN, AND ANY CLAIM OF INCONVENIENT FORUM WITH RESPECT TO, THESE COURTS.

6.Waiver of Jury Trial. EACH OF PARTY A AND PARTY B HEREBY IRREVOCABLY WAIVES (ON ITS OWN BEHALF AND, TO THE EXTENT PERMITTED BY APPLICABLE LAW, ON BEHALF OF ITS STOCKHOLDERS) ALL RIGHT TO TRIAL BY JURY IN ANY ACTION, PROCEEDING OR COUNTERCLAIM (WHETHER BASED ON CONTRACT, TORT OR OTHERWISE) ARISING OUT OF OR RELATING TO ANY TRANSACTION OR THE ACTIONS OF PARTY A OR ITS AFFILIATES IN THE NEGOTIATION, PERFORMANCE OR ENFORCEMENT HEREOF.

Very truly yours,

WELLS FARGO BANK, NATIONAL ASSOCIATION

By: /s/ Cathleen Burke

Designated Signer

Name: Cathleen Burke

Agreed and accepted by:

PINNACLE WEST CAPITAL CORPORATION

By: /s/ Chris Bauer

Name: Chris Bauer

Title:    Vice President and Treasurer