British Gas has announced it is to introduce a "green energy" unit.
British Gas New Energy will offer rooftop solar heating panels and allow customers to offset their carbon dioxide emissions through schemes that buy credits from other firms or countries whose own emissions are well within targets.
Parent company Centrica pledged to cut energy use in its own UK buildings by 10 per cent this year and is working on developing a fuel cell domestic boiler that could halve household carbon dioxide emissions.
"We have reason to believe that in market turnover terms, this space will be worth several billion pounds a year in the next few years," the unit's managing director, Gearoid Lane, said.
The average UK home emits five tonnes of carbon dioxide a year, accounting for about a quarter of the household's total emissions, British Gas says.
Another quarter comes from travel, and the rest derives indirectly from leisure activities and the consumption of food, clothing and furniture.