Britain's largest energy supplier, Centrica, is to sell domestic micro-generators from Windsave to UK households for use on rooftops. In an initial pilot this year Centrica subsidiary British Gas will install the units on properties in Scotland and south-west England. If successful, sales will be rolled out across the country. The tiny turbine will produce up to 1 kW of electricity, supplementing the property's supply from its electricity retailer, and will start to generate at wind speeds of 3-4 metres a second. British Gas expects the wind turbine to retail for around £1500. But the device will also be able to earn its owners an income through sale of the Renewables Obligation Certificates associated with its generation. Windsave, based in Glasgow, expects to be floated on the Alternative Investment Market of the London Stock Exchange in early 2006.