LONDON -- Nissan announced a new home energy-storage device Monday, made out of recycled batteries sourced from its Leaf electric cars.

The xStorage system, which Nissan unveiled at an event in East London and is produced in partnership with power =-management company Eaton, is essentially the company's  answer to Tesla's Powerwall.

The product, which will be powered by 12 Nissan Leaf battery modules, connects to a residential power supply.

It charges up when either renewable energy (from, say, solar panels) is available, or when energy from the grid is cheap (typically at night). Then it releases that energy, powering the house, when energy costs are higher. It will also allow consumers to sell energy back to the grid, Nissan say.

The xStorage battery is being touted by the company as "the first... to provide a fully integrated energy storage unit for homeowners." It will be installed by certified installers and connects to a smartphone app that will allow consumers to manually switch between energy sources.

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The xStorage will be available in the UK starting in September this year for £3,200 (approximately $4,600). There are currently no plans for distribution in the U.S.

While the headline price is higher than Tesla's Powerwall, Nissan say that it's all inclusive, including converters and installation and so on, and works out cheaper than the Powerwall overall.

"Our system will be provided to end users completely ready to use, with all required elements including cabling and installation by a certified professional, at a starting price of 4,000 euros for 4.2 kilowatt-hours (kWh) nominal," Eaton Electical EMEA's Vice President of Marketing Cyrille Brisson said. (The Powerwall offers 6.4kWh of storage capacity.)

"Our policy is to avoid hidden extra costs and achieve a lower total cost of ownership than other major offers already announced."

Nissan and Eaton expect to shift 100,000 of the units within the first five years.

The carmaker also unveiled its Fuel Station of the Future concept at the event Tuesday, a conceptual look at how their Leaf vehicles and xStorage batteries could potentially power homes and offices -- and give energy back to the grid -- in the future.

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