(Bloomberg) -- California startup Lunar Energy Inc. launched a home power storage system this week with Sunrun Inc. as its first installer in a bid to enter the residential battery market dominated by Tesla.

Lunar Energy started taking reservations for its Lunar System, which provides all-in-one residential solar generation and storage, including battery modules that can provide 10 to 30 kWh of backup power. 

Demand for battery storage is growing rapidly as heat waves and other extreme weather conditions drive up power consumption, threatening to overwhelm grids across the US. Battery storage can smooth out solar power supply, allowing homeowners to keep the lights on when the sun is not shining and ease demand when grids are under stress. 

“There are 75 million homes in the country and only 4 million have solar, and a quarter million of those have home batteries,” Lunar Chief Executive Officer Kunal Girotra said Friday in an interview on Bloomberg Television’s “Bloomberg Technology” with Ed Ludlow. Girotra is a former executive of Tesla Energy Operations Inc., a division of the electric vehicle company that produces Lunar’s primary residential energy storage competitor, the Tesla Powerwall.

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Sunrun, one of the biggest residential solar installers in the US, owns a 37% stake in the startup and has preferential access to Lunar’s technology. Installations will begin in California this fall before expanding to other parts of the country, Lunar said.

“One of the things we’re most excited about isn’t providing opportunities for customers to defect from the grid,” said Sunrun Chief Executive Officer Mary Powell in the same interview. “We can create a more affordable, resilient grid for all Americans.”

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