Electric vehicle drivers use up to 80 percent more electricity if they charge at home and so can benefit from tariffs which pass on cheaper overnight wholesale electricity costs, British Gas said.

It said it would calculate annual costs based on how much electricity an EV owner has used in the past in the home

Its estimate of costs will assume that 38 percent of electricity will be used during off-peak hours

British Gas said average EV owners typically charge their vehicles about three times a week during off-peak hours, and twice a fortnight during peak hours using 10 kilowatt hours of electricity a time

"This is our first residential EV product. Over the coming months, we will launch further electric vehicle charging services to both residential and business customers," said Peter Simon, customer propositions and product director at British Gas

There are currently 200,000 electric vehicles on the road in Britain and this is forecast to grow to 1.4 million by 2025.