The industry also faces quality problems. Proven Energy , a Scottish company that is one of the world’s major manufacturers of small wind turbines, recently announced that it was “aware of a potential manufacturing defect” in one of its turbines and advised owners of that model “to place their wind turbines on brake as soon as it is safe to do so.”

This year, both California and New Jersey — two states that have aggressively embraced renewable energy — put their small-turbine incentives programs on hold, at least temporarily, after problems surfaced.

In New Jersey, the issue was defects in a few turbines, according to Mr. Flowers. In California, “some scammers figured out some loopholes in the program,” said Mr. Bergey, who is also the president of the Distributed Wind Energy Association. Effectively, he said, they found a way to qualify for rebates that were higher than the cost of the equipment. “The market has literally stopped there,” said Mr. Bergey, referring to California. “We’re hoping it will get going again shortly.”

Mr. Gipe, the industry expert, said that the structure of any policy for establishing incentives for small turbines is crucial. Britain, with its feed-in tariff that rewards the production of electricity, got it right, he said.

“The important thing is that all the risk for installing and operating these small wind turbines is on the person who bought them and put them in the ground — not on the consumer and not on the ratepayers,” Mr. Gipe said.

Some of the reputation problems of the small-turbine industry may be eased by a new program in the United States to provide certification for such units. Leading turbine makers including Bergey Windpower and Southwest Windpower are putting their machines through the process. Mr. Flowers said that the first certifications for small turbines would probably be issued in six months to a year.

Meanwhile, new markets are opening up. In the United States, universities have shown more interest in small wind turbines because of government aid. The University of North Texas, for example, received a $2 million grant this year thanks to stimulus measures to plant three 100-kilowatt turbines near its new football stadium.