Energy company Npower will announce plans on Tuesday for Britain's first mass-market solar electricity service.
Owned by Innogy, Npower has formed a partnership with Solar Century, a company that installs solar panels. They are developing a solar energy "account" where customers will be able to sell any excess electricity they generate to Npower.
During times when there is insufficient daylight to generate enough power, users will be able to buy electricity back from Npower.
Jeremy Leggett, chief exec- utive of Solar Century, said: "This is an exclusive agreement with Npower. We will have access to five million customers." He hoped this would persuade people to switch from dirty to green energy.
A typical solar installation costs £9,500. But the Department of Trade and Industry provides grants of up to 50 per cent of the cost.