$3,000 device to power entire home for eight hours

Have you ever heard of a battery that can power an entire household for as long as eight hours? Tesla founder Elon Musk has unveiled one.

Musk introduced the Powerwall device at a press conference in California recently and termed the $3,000 battery as "revolutionary" and one that could "change the world".

The device might soon be available in the open market. Powerwall is three-feet wide and four-feet tall, weighs 100 kg, and can be installed both on and inside the wall. Powerwall can be used as back up power in the case of an emergency, or to store power from renewable energy sources.

"Our goal is to fundamentally change the way the world uses energy...It sounds crazy, but we want to change the entire energy infrastructure of the world to zero carbon," tech site Mashable quoted Musk as saying at the event.

The daily use version has a capacity of 7-kilowatt-hours, which is around a quarter of a home's daily usage.

According to that figure, a single, fully-charged Powerwall device would be able to meet a quarter of a home's energy needs on any given day.

However, it would likely last far less time than eight hours during the mornings and evenings, when homes use the vast majority of their electricity.

Musk said that the devices can be stacked together to provide more energy.

The system would let homeowners with solar panels or other sources of renewable energy easily store their energy at home, rather than the current model whereby they sell power back to energy suppliers as it is produced, then buy it again during peak times.

It could also let savvy consumers take advantage of power companies' lower rates during the night and use the cheaper, stored energy during peak periods.