Material Event (Form 8-K)

On June 29, 2026, Southwestern Public Service Company, a New Mexico corporation ("SPS"), issued $650,000,000 in aggregate principal amount of 5.300% First Mortgage Bonds, Series No. 13 due 2036 (the "2036 Bonds") and $550,000,000 in aggregate principal amount of 5.875% First Mortgage Bonds, Series No. 14 due 2056 (the "2056 Bonds" and together with the 2036 Bonds, the "Bonds") pursuant to an Underwriting Agreement among SPS and BMO Capital Markets Corp., BofA Securities, Inc., Morgan Stanley & Co. LLC, RBC Capital Markets, LLC, and Wells Fargo Securities, LLC, as the representatives of the several underwriters named therein. The Bonds are being issued pursuant to the registration statement on Form S-3 (File No. 333-278797-01) (the "Registration Statement"). A prospectus supplement relating to the offering and sale of the Bonds was filed with the Securities and Exchange Commission on June 24, 2026. The Bonds will be governed by the Indenture, dated as of August 1, 2011, by and between SPS and U.S. Bank Trust Company, National Association (as successor to U.S. Bank National Association), as trustee, as supplemented by Supplemental Indenture No. 13 dated as of June 15, 2026.

This Current Report on Form 8-K is being filed to report as exhibits certain documents in connection with that offering and sale for incorporation by reference into the Registration Statement.