Tesla and Southern California Edison opened up the world’s largest battery storage facility on Monday.

The facility at the SCE utility’s Ontario, Calif., station hosts about 400 Tesla PowerPack units on a 1.5-acre site. It can store enough energy to power 2,500 homes for a day or 15,000 homes for four hours, the companies said.

SCE’s move with Tesla was spurred by a disaster the utility faced starting in 2015. A natural gas leak at Aliso Canyon, owned and operated by Sempra Energy and located near Los Angeles’ Porter Ranch neighborhood, released thousands of tons of methane before it was sealed by Sempra in February 2016.

Since then, SCE and other utilities have been pursuing energy storage deals to secure energy supply to avoid blackouts and price spikes. Tesla Energy won the very large contract with SCE in September and set out for the fast-paced setup and launch this week.

Bloomberg reported that the Tesla facility is coinciding with the launch of two other huge facilities in southern California, built by AES and Altagas. Combined, these three storage facilities will make up 15 percent of the battery storage installed globally last year.

The large energy storage plant is also part of California’s campaign to keep electricity flowing during disasters and to reduce reliance on fossil fuels.

It’s coming together much faster than the state expected.

“It’s sort of hard to comprehend sometimes the speed all this is going at,” Tesla Chief Technology Officer J.B. Straubel told Bloomberg. “Our storage is growing as fast as we can humanly scale it.”

Finding this viable, cost-effective energy storage system also ties together with an initiative the state has been pushing and one that Tesla CEO Elon Musk backs: making renewable energy like solar and wind power practical. Battery storage is critical for these energy sources to grow, especially during variable weather patterns that impact solar and wind.

Musk wants Tesla to play its part in fighting climate change with electric vehicles, solar energy through its SolarCity company, and energy storage products and grid-storage plants like the one opened this week.

The declining cost of lithium-ion batteries is making energy storage as appealing as the cost-competitive electric cars coming to market. Lithium-ion batteries reportedly cost about half as much today as they did in 2014.

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“I had relatively limited expectations for the battery industry in advance of 2020,” said Michael J. Picker, president of the California Public Utilities Commission to the New York Times. “I thought that it would not really accelerate and begin to penetrate the electric grid or the transportation world for a while to come. Once again, technology is clearly moving faster than we can regulate.”

That Tesla Energy news followed another Tesla event last month on the battery side of the business. Tesla and Panasonic announced that mass production of lithium-ion cells had started at the Gigafactory in Nevada. That plant will make batteries for the Tesla Model S, Model X, and upcoming Model 3. It’s also producing battery cells for the company’s Powerwall 2 and Powerpack 2 energy products, Tesla said.

Production of cells for the Model 3 is expected to begin in the second quarter. Tesla is preparing to manufacture 500,000 or more electric vehicles per year starting in 2018, with the Gigafactory producing the needed battery packs.

Tesla expects to set another record that follows the world’s largest battery story facility that opened this week. The company plans on becoming the world’s biggest producer of lithium ion batteries in the world once the Gigafactory reaches full capacity.