The system will be priced at under £6,100 ($10,000) when it goes on sale in America next year, with additional local rebates and extra work required for fitting pushing the cost down or up respectively.

Included in the package is SunPower’s E18 solar panels, claimed to be 50% more efficient at generating electricity than conventional solar panels, despite their smaller size. The installation is backed by a 25-year warranty and features a monitoring system to allow owners to track its performance via the internet or an iPhone app.

On average, the panels should be able to generate 3,000 kilowatt hours of electricity per year – enough to offset 12.000 miles of driving, Ford said.

The system is designed to offset the energy used from charging Ford’s forthcoming plug-in vehicles, with SunPower able to support the carmaker’s roll-out in 19 markets worldwide. European pricing has yet to be announced. Ford said in its announcement that the SunPower system will be compatible with the Best Buy home charging units supplied as part of a partnership announced in January.

Mike Tinskey, Ford’s director of global vehicle electrification and Infrastructure, said: ‘Under the “Drive Green for Life” programme, Focus Electric owners can reduce their total cost of ownership by generating enough energy from their high efficiency SunPower rooftop solar system to offset the electricity required to charge the vehicle at night.

‘It’s an eco-friendly solution that perfectly complements our plug-in products and other green initiatives. The goal of working with both SunPower and Best Buy was to offer Focus Electric owners solutions to charging needs that help lower the vehicle’s overall cost of ownership’