Homeowners who splash out on wind turbines and solar panels are being paid for the electricity they generate, even when they use it all themselves.

The perk can be worth several hundred pounds a year and is being subsidised by other customers through their electricity bills. It is part of a government package to encourage alternative energy sources C but the generous payouts have surprised some homeowners.

Its staggering, said Harry Metcalfe, publisher of the supercars magazine Evo, who has installed a 30ft wind turbine in the grounds of his large farmhouse near Burford in the Cotswolds. I thought Id just get paid for the surplus, but not the electricity that I use myself.

His turbine provides power for his house and for underfloor heating in his garage, where he has a small fleet of sports cars. I got the turbine because I love technology and am naturally mean when it comes to paying bills, he said.

Under his agreement with his energy company, Ecotricity, Metcalfe is paid for 9p for every unit of electricity his turbine generates C whether or not it is exported to the national grid. It works out at more than £700 a year and he calculates that the payback period on his £13,000 investment will now be only about seven years.

Dale Vince, managing director of Ecotricity, said that householders facing higher energy bills might balk at the payouts but they were an important incentive to encourage microgeneration, or domestic green power. The current rate is actually probably too low to bring about the change the government wants to see, he said.

The payouts are made under the Renewables Obligation Certificate scheme, which rewards power generators, companies and householders who create green power. The scheme costs up to £870m a year and adds about £10 to the average electricity bill.

Homeowners in urban areas are unlikely to benefit, though. Energy advisers say that the type of turbine the Conservative leader David Cameron has installed at his west London home does not generate enough power.

The cash can also be claimed if homeowners install solar panels. Nick and Fiona Mills, both 50, who live in Stroud, Gloucestershire, had 14 panels fitted in April 2007. Their electricity company, Good Energy, pays them 9p per unit of electricity. The panels meet almost all their power needs, and in the first year, they were paid £83 by Good Energy.

The Department for Business and Enterprise said the subsidies were justified because home generators did not produce carbon emissions from fossil fuels. The government wanted 10% of the UKs electricity to come from renewable sources by 2010, and to double that by 2020.