Tucson, Ariz. – Tucson Mayor Regina Romero and other local officials today joined Tucson Electric Power (TEP) to celebrate the commencement of operations at an expansion of our community’s largest local battery energy storage system.

TEP’s Roadrunner Reserve includes 400 megawatts (MW) of battery energy storage in southeast Tucson capable of powering nearly 85,000 homes for four hours. Last year, TEP invested $350 million to bring the first 200 MW of the system online in time to serve customers during record-setting summer usage.

In June, TEP brought another 200 MW into operation. Romero and other local leaders including Ward 5 Council Member Selina Barajas, Ward 3 Council Member Kevin Dahl, District 2 Pima County Supervisor and Board Vice Chair Dr. Matt Heinz, and Arizona State Senator Priya Sundareshan joined TEP officials at a ribbon cutting ceremony this morning to celebrate the addition of a system that supports reliable energy service for TEP customers throughout the Tucson area, even during extreme weather conditions.

“This project helps ensure Tucson has reliable energy to support the needs of our community while helping TEP to take greater advantage of solar resources,” said Susan Gray, TEP’s Chief Executive Officer. “The City of Tucson and Tucson Electric Power have different roles and responsibilities, but we’re working toward many of the same goals: supporting economic opportunity, strengthening resilience, investing in infrastructure, and building a more sustainable future for the neighbors we serve. Roadrunner Reserve is more than a battery facility. It’s a symbol of our commitment to reliability, innovation and a cleaner energy future.”

“As Tucson experiences hotter summers and more frequent extreme heat, building a resilient energy system is essential to protecting our community,” said Tucson Mayor Regina Romero. “Investments in battery energy storage help improve reliability during times of highest demand, expand our ability to use renewable energy, and ensure residents, businesses, and critical services have the energy they need when it matters most. This is an important investment in Tucson’s safety, resilience, and future.”

Roadrunner Reserve is helping TEP to make the most of renewable energy while reducing reliance on fossil fuels as it pursues an aspirational goal to achieve net zero carbon emissions by 2050. Energy storage systems are typically charged in the late morning when solar energy is abundant and grid usage is relatively low. TEP then deploys that reserved energy in the late afternoon and early evening, when energy use typically peaks and market prices for energy are highest.

The system played a critical role in supporting resilient grid operations on Aug. 6, 2025, when our community’s energy needs surpassed forecasts and set a record hourly demand peak of 2,502 megawatts (MW). The system helped to keep customers cool through the 111-degree day. The expanded system has also helped to maintain service for customers during recent grid disturbances.

Roadrunner Reserve uses lithium iron phosphate battery units, which offer longer life and safer operations than alternative technologies.

TEP provides safe, reliable electric service to 457,000 customers in Southern Arizona and maintains one of the nation’s most reliable electric grids. For more than 130 years, TEP has invested in the energy infrastructure that powers homes, businesses, and community institutions while advancing toward a cleaner, more resilient energy future. Learn more at tep.com.

TEP and its parent company, UNS Energy, are subsidiaries of Fortis Inc., a leader in the North American regulated electric and gas utility industry. For more information visit fortisinc.com.

News Media Contact:
J.D. Wallace
520-801-6392
jd.wallace@tep.com