Many home turbines fall short of claims, warns study

Home wind turbines are generating a fraction of the energy promised by manufacturers, and in some cases use more electricity than they make, a report warns today. The results of what is thought to be the most comprehensive study undertaken of the industry show the worst performers provided just 41 watt-hours a day - less than the energy needed for a conventional lightbulb for an hour, or even to power the turbine's own electronics.

On average the turbines surveyed provided enough electricity to light an energy-efficient house, but this still only represented 5%-10% of the manufacturers' claims, said consultants Encraft. The findings will be an embarrassment for an industry which was an early winner from the small but high-profile rush to adopt green technologies. Trendsetters included the actor Pete Postlethwaite at his country house in Shropshire and novelist Iain Banks at his home near Edinburgh. Opposition leader David Cameron applied for permission for a turbine on his west London home.

But the results also prove that when turbines are put up in the right places they are a good investment, said Matthew Rhodes, Encraft's managing director. "Sadly, an average semi-detached house, like the areas where most people live, where there are obstructions like trees and buildings, are poor locations," he said. The "vast majority" of customers had been poorly advised, said Rhodes: "There's a risk they [customers] will go off the whole agenda."

The study, funded by the British Wind Energy Association and the government, looked at turbines made by five manufacturers in four rural, 10 suburban and 12 urban sites for a year. It found the best performing turbines would generate "clean" electricity equivalent to that needed to manufacture them in less than two years, while the worst performing ones would take 40 years.

However, Alex Murley, the BWEA's micro-generation expert, said the study had been skewed unfairly, with few sites, and too many in areas with poor wind.

New codes of conduct for manufacturers and installers had been introduced, he added. The latest BWEA figures show 1,000 building-mounted small turbines had been installed in the UK by the end of 2007, with 900 of those installed during that year.