North America | June 16, 2025

California approves world’s largest solar battery

The California Energy Commission (CEC) has given the go‑ahead to the Darden Clean Energy Project (DCEP), to be the first facility approved under the state’s new Opt‑In Certification programme.

 

world's largest battery energy storage system with solar panels AI

Image for illustrative purposes

A new champion in clean energy

Set on 9,500 acres of land in western Fresno County—land that is no longer farmed—the DCEP will be the world’s largest solar‑plus‑storage installation. It includes a 1,150 MW solar array made up of about 3.1 million panels and a battery energy storage system (BESS) of equal capacity: 1,150 MW with up to 4,600 MWh of storage. That is sufficient to power 850,000 homes for four hours straight.

What makes the Opt‑In Certification programme different

Introduced by Assembly Bill 205, the Opt‑In Certification programme offers a consolidated, state-level approval pathway. Projects that opt in must complete environmental reviews within 270 days of a complete application, unless major changes are made mid‑process. It aims to accelerate the delivery of large clean energy projects like the DCEP.

Placing California at the top of the grid energy storage league

California already ranks second globally, after China, in battery storage with more than 15,700 MW across over 200 utility-scale systems and hundreds of thousands of smaller installations. Notably, in 2024 the state added 7,000 MW of clean energy in a single year—the highest annual increase yet—and has added 25,000 MW over the last five years.

The grid reached 100% clean energy at least part of the day on 60% of days last year. So far this year, through May, that figure is even higher: 138 out of 151 days, or 91%.