Project Overview
Mortenson served as the Engineering, Procurement, Construction contractor for Calpine Corporation’s Nova Power Bank energy storage project, delivering both battery storage and substation scopes. The project transformed a decommissioned power plant site into a large-scale energy storage facility supporting power reliability across the Southern California Edison grid.
Key Takeaways:
- One of the Industry’s Largest Standalone Storage Projects: 680 megawatts / 2,720 megawatt-hours of storage capacity designed to power as many as 680,000 California homes.
- Sustainable Site Transformation: A decommissioned natural gas-fired power plant site was repurposed into an energy storage facility using major portions of the existing facility.
- Flexible Grid Reliability: The facility provides instantaneous, flexible power to better serve California’s peak power demand.
- Major Battery and Substation Scope: Nearly 1,200 battery enclosures connect through three 500kV substations, each with seven feeder breakers.
- Fast Phased Delivery: Phased turnovers began less than 12 months after construction started in August 2023, with the full project completed in June 2025.
- Delivery Method
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Engineer, Procure, and Construct
- Additional Project Facts
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680 Megawatts Energy Storage
3x 500kV Substations
Completion Date: 2025
Mortenson was chosen as the Engineering, Procurement, Construction contractor for both the battery storage and substation scopes for Calpine Corporation’s Nova Power Bank energy storage project. This 680 megawatt / 2,720 megawatt-hour project is one of the largest standalone storage projects in the industry and is set to power as many as 680,000 California homes across the Southern California Edison grid.
Built on the site of a decommissioned power plant previously known as the Inland Empire Energy Center, the natural gas-fired generators were decommissioned and removed so the site could be transformed into an energy storage project. Major portions of the existing facility, including foundations, structures, and electrical infrastructure, are contributing to a highly sustainable transformation which will better serve the state’s peak power demand.
The project is a facility that will provide instantaneous, flexible power and grid reliability for the people of California. Repurposing existing assets comes with design and construction challenges but is a responsible and effective way to bring energy storage to those that can benefit from it the most.
The site uses nearly 1,200 battery enclosures utilizing BYD Cube Pro and Power Electronics 4200M2 technology connected through three 500kV substations, each with seven feeder breakers.
Construction for the project began in August 2023 with phased turnovers starting less than 12 months after breaking ground. The first phases of the project came online in 2024 and the project was fully completed in June of 2025.
