Home batteries re-charge overnight, when energy companies typically charge less for electricity. They can be used during the day to power a home. The cost for the battery is in the thousands, but many utility companies will offer rebates.

Musk announced the event on Twitter, hinting then that the new product is not a new electric car. The event was held at Tesla's Hawthorne, California, Design Studio.

Some of the company's early plans were reveled at a battery conference last year, including a 10 kilo-Watt hour residential battery and a 400 kWh commercial/utility battery for large buildings.

The home stationary battery will be called the Powerwall, and it will cost $3,500 for a 10kWh unit. That unit is optimized to deal with serving a house if the traditional power grid goes down. A cheaper, $3,000 version will have a 7kWh capacity, and it will be able to help a house with solar panels deal with the daily fluctuations in energy supply.