Tesla has started mounting its home energy lithium-ion battery – dubbed the Powerwall – in select homes.

“We are currently in production and have started installing Powerwalls with pilot customers,” Tesla spokeswoman Alexis Georgeson told Electrek. “Over the next few weeks we will continue to ramp up volume production.”

Tesla Powerwall

Tesla Powerwall specifications.

The units being installed are 7 kilowatt-hours (kwh) Powerwalls, the smaller of Tesla’s two home energy storage systems. It’s designed to store solar or off-peak electricity for daily household use and allows multiple units to be connected for up to 63 kwh of energy.

Tesla also plans to offer a larger 10 kwh Powerwall as a battery backup for occasional use. Installations aren’t set to begin until 2016; Tesla is likely waiting for its Gigafactory to be operational to build these larger units.

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North America has been picked as one of the first markets to receive Powerwalls, along with Australia, Germany, Switzerland and Austria.