The world’s largest battery project has been brought on line in California, just in time to help prevent blackouts amid an historic heatwave.

The 250MW/250MWh Gateway Energy Storage project in San Diego County, operated by grid infrastructure developer LS Power and using LG Chem Lithium-ion cells, beats the previous record held by the 150MW/193MWh Hornsdale Power Reserve in South Australia, which uses batteries supplied by Elon Musk’s Tesla.

The Gateway project will improve grid reliability and reduce customers’ energy costs, according to New York-based LS Power.

The current heatwave in California and the consequent increased power demand for air conditioning has threatened to bring down the state’s overloaded grids, especially at those times when the sun goes down and solar power drops off. The crisis forced grid network operator California ISO to introduce rolling blackouts last weekend, with more outages threatened.

So far, only 230MW of Gateway’s battery cells have been energized, but the entire project is due to be fully commissioned by the end of this month. The facility's energy capacity will be increased to 750MWh of storage next summer, and 1GWh at a later date.

“By charging during solar production or off-peak hours and delivering energy to the grid during times of peak demand for power, our battery storage projects improve electric reliability, reduce costs and help our state meet its climate objectives,” said LS Power’s head of renewables, John King.

LS Power is set to beat its own record in the near future, with the first phase of its 316MW Ravenswood Energy Storage project in New York City due to come on line next year.

The developer also has two other 100MW-plus storage systems in the pipeline, the 200MW Diablo and 125MW Leconte projects, both in California.