Independent studies of home-based wind turbines show they often fail to generate as much electricity as their makers claim they will.
The poor performance has led to customer complaints and increasing government scrutiny of the industry.
Jon Christenson of Windom, Minn. is one customer not getting as much production from his wind turbines as he thought he would.
Christenson says the three turbines he installed at his house in Windom, Minn. produce a good share of the electricity he uses. But he says that share isn't has high as he expected it would be. Generally, they fall about 25 percent short.
"That's about typical, about 75 percent of what they're rated at," said Christenson.
Christenson, though, is satisfied with that level of production. And maybe he should be. Studies show he's probably doing better than most wind turbine owners.
Complaints about electricity output are so common, the state of Massachusetts decided to conduct its own testing program.
"It confirmed our concerns," said Philip Giudice, commissioner of the Massachusetts Department of Energy Resources.
Giudice says the state tested 19 home-based wind machines, and all fell well short of their manufacturers' production estimates.
Even the best performing turbine generated only about 60 percent of what the company said it would. The worst generated a tiny 2 percent. All told, the 19 machines' electricity production averaged only about one-quarter of the manufacturers' estimates.
Giudice says the tests results should serve as a cautionary tale for anyone thinking of putting up a wind turbine in their backyard.
"I do think that all of us need to continue to learn from experience and take action accordingly," said Giudice.
"Wind turbines for the private landowner, I think, are a waste of time."
Among the wind machines tested in the Massachusetts study were several made by Bergey Windpower, which is based in Oklahoma. Company President Mike Bergey says he's looked at the results, and calls them a wakeup call for the industry.
Bergey says wind turbine buyers need to do a better job researching specific sites before they install a turbine.
"The basic problem there is not with the machines themselves," said Bergey. "It's with average wind speeds that are lower than historical average. Towers that aren't tall enough. And dealers that were overpromising the performance."
That may sound like Bergey is trying to blame everyone but his own company.
But industry analysts say consumers often make mistakes in putting up their wind machines, either by placing them too low to the ground to catch the strongest winds, or by putting them too close to buildings or other obstructions that reduce wind speed.
Bergey says he still sees a bright future for small wind production, even though some consumers have had bad experiences.
Count Kevin Clayton among that group.
"Wind turbines for the private landowner, I think, are a waste of time," said Clayton.
Clayton put up a wind turbine on his farm near Traverse City, Mich., last October. It's turned into an $18,000 disappointment. He says he's only getting 20 percent of the promised electricity. Things are so bad, he says he'll probably pull the plug on the project.
"I'm going to give it another six months to a year and then I'm going to take it down," said Clayton.
Because of experiences like that, more testing is on the way. The federal government is about to release more research data. Its past evaluations shows that wind turbines generally need winds stronger than homeowners are likely to find on their land to meet production estimates.
The most ambitious testing program is something called the Small Wind Certification Council. The council is expected to begin testing wind turbines this year for electricity output, durability and safety. It's being funded by several government agencies, including the federal National Renewable Energy Laboratory.
The council comes on line at a critical moment for the industry. Federal incentives are expected to promote a rapid growth in home-based wind systems, like the one Jon Christenson of Windom built.
"I come out every day and I see them turning, and I just get a good feeling," said Christenson. "I love the independence of generating my own power."
Christenson says his main motivation for using wind turbines is political -- he wants to demonstrate that clean energy is possible. But he concedes the electricity he produces will not be enough to pay off the cost of the system.
His political motivation is something he shares with many owners of small wind turbines. But even the strongest motivations can fade if the machines fall short of expectations.
That's the problem facing the industry. It could squander its clean energy good will unless the performance issues are solved.