US electric carmaker Tesla Motors has unveiled batteries that can power homes and businesses. Chief executive Elon Musk announced the firm would build batteries that store solar energy and serve as a back-up system for consumers during blackouts. The device would allow consumers to get off a power grid or bring energy to remote areas that are not on a grid.

"Tesla Energy is a critical step in this mission to enable zero emission power generation," the company said in a statement and the move could help change the "entire energy infrastructure of the world". The system is called Powerwall, and Tesla will sell the 7kWh unit for $3,000 (?1,954), while the 10kWh unit will retail for $3,500 (?2,275) to installers.

Analysis: Richard Taylor, BBC News, San Francisco

Tesla's move into so-called "stationary storage" is a market with enormous growth potential: as the world slowly moves away from fossil fuels, it is seen as critical to a more widespread adoption of "clean" energy sources like solar and wind.

Friends of the Earth's renewable energy campaigner Alasdair Cameron said having solar panels and a home battery in the future could become as common as central heating. "Just as the internet changed the way we use information so renewable sources, like wind and solar, are changing the way we make and use energy - and electricity storage is an important part of that change," he said.

Vocabulary:

Blackout, power grid, zero emission, infrastructure