(Bloomberg) -- The biggest battery storage system in the U.S. connected to California’s electricity grid, giving the state more flexibility to bank excess solar power generated during the hottest parts of the day and deploy it later.

The California Independent System Operator, which manages a grid that powers powers 80% of California and a small portion of Nevada, added 62.5 megawatts to its storage capacity in June, when the initial phase of LS Power Group’s Gateway Energy Storage project came online in San Diego.

If all planned projects are completed on schedule, the grid operator’s storage capacity will expand six-fold by the end of 2020 from 136 megawatts at the beginning of the year, the ISO said in a statement. Current capacity is 216 megawatts.

Storage will play a key role in the state’s efforts to integrate renewables, said Steve Berberich, ISO president. He predicts that as much as 15 gigawatts of battery storage will be needed to help the state reach its goal of being carbon neutral by 2045.

(Adds details on storage capacity in third paragraph.)

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