Tesla’s next innovation could take you off the electric grid. The tony car manufacturer is planning to unveil a new lithium-ion battery pack that homeowners could buy to store and supply their own energy, CEO Elon Musk said during an earnings call Wednesday.

“We have the design done, and it should start going into production in about six months or so,” Musk said.

Details on the batteries were sparse, but an obvious use case would be placing them in homes equipped with solar panels to store excess energy. Solar energy company SolarCity already offers Tesla battery packs in some markets that customers can use to store energy and use as a kind of emergency generator. Musk is the chairman of SolarCity and its largest shareholder.

In addition to selling to residential customers, Tesla could also sell batteries to utilities trying to increase energy efficiency. Tesla’s chief technology officer said the company was talking to “almost all” the utilities currently experimenting with battery storage technology.

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