US electric carmaker Tesla Motors has unveiled batteries that can power homes and businesses

as it attempts to expand beyond its vehicle business.

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 plans to start shipping the units to installers in the US by this summer.

In a highly anticipated event near Los Angeles, Mr Musk said the move could help change the

"entire energy infrastructure of the world".

"Tesla Energy is a critical step in this mission to enable zero emission power generation,"

the company said in a statement.

The rechargeable lithium-ion battery unit would be built using the same batteries Tesla

produces for its electric vehicles, analysts said.

The system is called Powerwall, and Tesla will sell the 7kWh unit for $3,000, while

the 10kWh unit will retail for $3,500 to installers.

To help comparisons, Tesla provided estimates of how much energy is used by different devices

in the home. A flat-screen TV uses about 0.1kWh, a tumble dryer 3.3kWh and a laptop 0.05kWh.

Energy comparison firm USwitch estimates that a small family in a three-bedroom house in

the UK uses about 3,200kWhs of electricity a year.

Mr Musk said the company would partner with SolarCity to install the home batteries, but

there would be more companies announced. Mr Musk is SolarCity's chairman and largest

shareholder.

The sales of battery storage systems for homes and businesses could yield as much as $4.5bn

in revenue for Tesla, according to Deutsche Bank.