Tesla’s latest virtual power plant is in Japan. The company announced Friday that it has been quietly installing its Powerwall batteries at homes on the island Miyako-jima since 2021 and now has over 300 installed. It’s the largest commercial virtual power plant in Japan, according to the statement.

Virtual power plants take advantage of solar panels and batteries in private homes. People with those setups can sign up to send extra power back to the electrical grid in their area, giving it an extra boost during situations when it’s at risk of a blackout. The grid can use that power instead of pulling from the gas-fired power plants typically used when the power supply is strained.

The virtual power plant is based on a program at local energy utility in Miyako-jima, Miyakojima Mirai Energy Co, that installs solar panels and storage batteries at no cost.

Tesla already has virtual power plants operating in California and Australia and is working on getting one off the ground in Texas — where it sees an opportunity to add a new source of power to a perennially unreliable grid. In California, people with Powerwalls installed in their homes can get $2 for every kilowatt-hour fed back into the grid when it’s under stress during emergencies or periods of high demand.

People living on Miyako-jima experience regular power outages during typhoons, and the Powerwalls help keep the lights on in individual homes. “During typhoons, lights are available, refrigerators are usable as usual,” said a Powerwall customer in a video released by Tesla.

Tesla said it plans to have 400 Powerwall units installed by the end of the year and 600 units by the end of 2023. The company then plans to expand to the rest of the Okinawa prefecture, which covers the constellation of islands stretching between the Japanese mainland and Taiwan.