Green Tech

Updated on May 29 at 7:25 a.m. PT with corrected figure of installed turbines last year.

Sales of turbines big enough to serve a single home or office building grew rapidly last year and are poised for even faster growth this year, according to a report from the American Wind Energy Association.

The report, published on Thursday (click for PDF), found that sales of small wind turbines smaller than 100 kilowatts grew 78 percent last year, even though there was a sharp drop-off at the end of last year and beginning of this year.

The actual number of small turbines installed, though, is very small at over 10,000 units last year, comprising 17.3 megawatts of added capacity.

Photos: Small wind turbines take shape

The stimulus act passed earlier this year gives people who buy a small wind turbine a 30 percent tax credit on the installation, which addresses the challenge of the upfront costs, which can be several thousand dollars to install.

Apart from policies, the other important factor to making a small wind turbine economical is siting. A study done that analyzed small wind installations in Massachusetts and one looking at roof-mounted turbines in the U.K. found that the machines underperformed manufacturers' claims.

The best location for small wind turbines, most of which are mounted on poles, is an area with an average wind speed of about 12 miles per hour, said Ron Stimmel, the small wind advocate at AWEA.

"It all depends on your wind resource to get a decent payback," he said. "You need a little bit of land so you're not talking cities, but mostly suburban and rural locations."

Many municipalities have height limitations on structures but turbines generally perform well when they are 30 feet above any structures in a 500-foot radius, he said.

"If you find the wind annoying or have trouble keeping things on your porch, then you probably have enough," Stimmel said.

Unlike large turbines, you don't need to put up a tower to get data on wind speed but customers should look at wind maps and rely on installers to assess the resource, he added.

The dominant small wind turbine design is essentially a smaller version of the three-blade horizontal axis large turbines used in wind farms. But there are now hundreds of different small turbines, some of which are designed for homes or structures such as streetlamps.