Generous federal and local rebates and credits have helped put wind power on a growing list of options that use the forces of nature to trim your electricity bill. But our early tests of one wind turbine suggest that you could save far less than the manufacturer claims—and wait decades for your investment to pay for itself.
Wind turbines are supposed to save by powering your home and sending or selling any unused energy they create to a utility so that it can credit you that amount. At about $11,000 installed, the Honeywell WT6500 Wind Turbine we're testing at our Yonkers, N.Y., headquarters costs less than many wind systems, even before rebates. It's warranted for five years and can be ordered through True Value stores, from dealers and online, and at some Ace stores. And it's among the few that can mount on a roof. Low noise is an added talking point for this 6-foot-diameter turbine, which was about as loud as a library whisper in our tests. Its bicycle-wheel design is also claimed to be easier for birds to see than three-blade turbines.
WindTronics, which makes the system, says it can deliver 18 to 23 percent of an average home's annual electricity needs, depending on wind speed. That should mean our system pays for itself in about six years, given the energy it should create in our area, the 30 percent federal tax credit for small turbines, and the thousands in state rebates.
But so far, we've seen only a fraction of the total power that WindTronics says we should for our area, even after several visits from a company-authorized installer. At that rate, the Honeywell wouldn't pay its way over its expected life of 20 years.
We'll be updating our data during the next year and will report on further developments as we continue testing. Still, our early results highlight some key steps to take before opting for any wind turbine:
Based strictly on wattage, the Honeywell produced roughly what's claimed for the low wind speeds we were able to generate in our tests. But finding out how much energy you'll save at your home could be challenging. For example, WindTronics' promotional material claims 2,000 kilowatt-hours per year at class 3 winds, which the federal government defines as 11.5 to 12.5 mph. Yet its online calculator (www.windknowledge.com) showed an output of just 1,155 kWh per year at the 12-mph average it predicted for our area. That amounts to about 10 percent of the 11,000 kWh per year the U.S. Energy Information Administration cites for a typical home—not the 18 percent WindTronics asserts. The company's website also includes an estimate of 1,500 kWh per year on average, depending on wind speed, height, and site location. But even that comes to just 14 percent of the government's annual energy-use estimate.
Manufacturer sites can give you average wind speeds by ZIP code. Those averages can be misleading, however. WindTronics' calculator gives a "good" rating to the 12-mph speeds it says our location should average. But that rating is at 164 feet, not the 33 feet or more the Honeywell requires for roofs. A government map of New York lists average wind speeds for our area below 10 mph, not 12 mph. Indeed, we've had to blow air into the Honeywell with two industrial fans to come close to that speed.
Hills, trees, and other obstructions can lower wind speeds on your property. A site analysis by the installer should account for that. WindTronics told us its installations require one and that it is adding an online analysis tool. Our factory-authorized installer didn't include a site analysis. And the tool comes months after the Honeywell hit the market in late 2010. WindTronics has since suggested that our site is inappropriate.
Wind forces and the more than 440 pounds for the turbine and support structure could exceed your roof's capacity. With any roof system, get a structural analysis from an engineer before buying. And though roof-mounted turbines may seem less obtrusive than pole systems, you might still need approval from your zoning board.