What if you could buy power at night, when it's cheap, and run your house off it by day, when it's expensive (and, in Japan at least, in short supply)? Nissan wants to give customers who buy its Nissan Leaf just this ability, by selling them special chargers for their electric cars that can be reversed to feed power back into a home.

The lithium ion batteries in a Leaf can store up to 24kWh (kilowatt hours) of electricity, which Nissan estimates is sufficient to power an average Japanese home for about two days. That means if the system was used for a few hours during the day, the car would still retain enough power to make trips.

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There are already systems that allow homeowners to store energy overnight, but using the Leaf saves homeowners the cost of buying a redundant, and expensive, bank of batteries.

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