Business Description

Pinnacle West Pinnacle West is an investor-owned electric utility holding company based in Phoenix, Arizona with consolidated assets of approximately $30 billion. We derive essentially all of our revenues and earnings from our principal subsidiary, APS. Since 1886, APS and its affiliates have provided energy and energy-related products to people and businesses throughout Arizona. APS is Arizona’s largest and longest-serving electric company and generates safe, affordable electricity in 11 of Arizona’s 15 counties. Our other active subsidiaries are El Dorado and PNW Power. Our reportable business segment is our regulated electricity segment, which consists of traditional regulated retail and wholesale electricity businesses (primarily electric service to Native Load customers) and related activities, and includes electricity generation, transmission, and distribution. Our reportable business segment activities are conducted primarily through our wholly-owned subsidiary, APS. 3 Table of Contents BUSINESS OF ARIZONA PUBLIC SERVICE COMPANY APS currently provides electric service to approximately 1.4 million customers. We own or lease 6,257 MW of regulated generation capacity, and we hold a mix of both long-term and short-term PPAs for additional capacity. During 2025, no single purchaser or user of energy accounted for more than 1.9% of our electric revenues. The following map shows APS’s retail service territory, including the locations of its generating facilities and principal transmission lines. 4 Table of Contents Energy Sources and Resource Planning To serve its customers, APS obtains power through its various generation stations and through PPAs. Resource planning is an important function necessary to meet Arizona’s future energy needs. APS’s sources of energy by type used to supply energy to Native Load customers during 2025 were approximately as follows: APS has a diverse portfolio of existing and planned resources, including biomass, biogas, coal, energy storage, geothermal, natural gas, solar, and wind. APS has an aspirational goal to be carbon-neutral by 2050, meaning that for any GHG emissions still produced by generation resources in 2050, APS will aim to offset these emissions elsewhere. In 2025, the share of APS’s energy supply derived from clean resources was approximately 58%, which includes energy from nuclear, renewables, and DSM as well as PPAs with clean resources. Maintaining a balanced and diverse portfolio of resources helps ensure continued reliable service to our customers in the most affordable manner possible. Every three years, APS performs an IRP, a comprehensive study to identify what resources will be necessary to safely, reliably, and affordably meet the demand and energy needs of its customers over the next 15 years. The latest IRP was released in 2023 and APS is currently developing its next IRP due to be filed with the ACC in August 2026. To help ensure competitive costs for resources, APS regularly issues competitive bid solicitations through the ASRFP process, with the most recent ASRFP being issued in 2025. These ASRFPs are open to bids for all resource types, including customer-scale (behind the meter) and utility-scale (in front of the meter) resources. As energy demand in Arizona continues to grow, APS remains committed to delivering reliable and affordable service to its customers, with a goal of achieving top quartile reliability compared to its 5 Table of Contents peers. Among other strategies, APS intends to achieve this goal through various methods such as relying on Palo Verde, one of the nation’s largest producers of carbon-free energy; seeking a balanced energy mix; managing demand with a modern interactive grid; promoting customer technology and energy efficiency; and optimizing regional resources. APS also intends to harden its infrastructure in order to improve resiliency, which involves system and operational improvements aimed at reducing the impact of extreme weather events and other disruptions upon APS’s operations. Wildfire safety remains a critical focus for APS and other utilities. APS has increased investment in fire mitigation efforts to clear defensible space around its infrastructure, continue ongoing system upgrades, build partnerships with government entities and first responders, and educate customers and communities.…