Wind turbines have a hypnotic allure. The Siren call of carbon-neutral electricity has led many environmentalists to dream of owning a backyard wind turbine.

Unfortunately, small wind turbines, unlike utility-scale wind turbines, are rarely cost-effective, even when installed at a good site. Installed at an average site, a wind turbine is little more than an expensive toy.

Most renewable energy consultants can share tales of small wind turbines that have disappointed their owners due to low energy production or frequent maintenance problems. That’s why it’s so important for wind-besotted greenies to do their homework before going turbine shopping.

Wind-generated electricity isn’t cheap
Even homeowners blessed with a fairly good wind site pay a steep price for wind-generated electricity.

One of only a handful of successful net-zero-energy homes in the U.S. is one owned by David Pill and Hillary Maharam of Charlotte, Vermont. Although most descriptions of their prize-winning house note that their 10-kW Bergey wind turbine generated more electricity during a 12-month period than the family used, few noted that their electricity is very expensive.

During its first year of operation, their wind turbine produced 6,286 kWh of electricity — worth about $627 at the current retail rate of $0.10 per kWh. That means that the $40,500 wind turbine will have a simple payback period of about 64 years. Unfortunately, the turbine is unlikely to last that long.

The same amount of electricity could have been generated by a 6-kW PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow. system, which the Pills could have installed for between $48,000 or $54,000. (For a somewhat different payback analysis, see David Pill's comment of 09/12/2011, posted in the comment section below this article.)

“In a good site, wind will be marginally cheaper than PV,” said Andy Shapiro, the Vermont energy expert who acted as a consultant on the Pill home. “But a spinning machine will have more maintenance over time.”

Another energy consultant with wind experience is Rob Meyers, energy efficiency and renewable energy integrator at South Mountain Company in Chilmark, Massachusetts. Meyers regularly encounters customers who are eager to install a wind turbine. “We always get these people to back up and agree to do efficiency measures first,” said Meyers. “Then we try to talk them out of installing a wind system. Our company has established an internal moratorium on residential wind installations. We feel that wind turbine manufacturers are undercapitalized and unable to adequately address maintenance issues. We feel that small residential wind is not really a viable solution.”

Arguments for going slow
There are four main reasons to hesitate before purchasing a wind turbine:

• Electricity generated by a small wind turbine is significantly more expensive than grid power.
• Many communities require landowners to jump through a series of regulatory hoops to obtain a permit for a tall tower. Even if a tower permit is approved, lingering resentments arising from testimony provided during the permitting process can sour relations with a turbine owner’s neighbors.
• A wind turbine is a mechanical device with many moving parts, and turbines are deliberately exposed to a site’s worst weather. To perform regular maintenance procedures, either someone will need to climb the turbine tower, or the entire tower will need to be lowered to the ground. Each maintenance event is a significant expense.
• Many studies have shown that most performance predictions for small wind turbines are exaggerated. Inaccurate forecasts are due to a variety of factors, including optimistic estimates of average wind speeds, inaccurate performance data from turbine manufacturers, and in some cases deliberate deception by turbine dealers.

One recent study by Shawn Shaw of the CADMUS Group, “Status Report on Small Wind Energy Projects,” examined the performance of 19 small (under 10-kW) wind turbines. The study found that on average, the wind turbines produced only 27% of the annual electricity production estimated by the wind turbine installers.

Shawn concluded, “Though the overall performance of the small wind systems installed in Massachusetts is lackluster thus far, the technology appears to be viable but highly subject to variables which are difficult to quantify (e.g. turbulence, wind speed, etc.). … In order to realize cost effectiveness on par with, or better than, PV systems, more action will be needed to educate installers and to weed out systems that will not meet performance expectations.”

Anyone thinking of installing a wind turbine should heed the advice offered in an unsigned article on the Web site of Home Power magazine: “Small-scale wind energy is not for the half-hearted, uninvolved, or uncommitted, and probably not for folks who never change the oil in their vehicles (or are willing to spend the bucks to hire someone to do the tower work). The North American landscape is littered with failed installations: Designs not fully thought-out or tested, machines bought because they were cheap, and installations that required more time and money for repairs than they ever yielded in electricity generated. Many of the failures were the result of wishful thinking and too little research.”

Whatever you do, resist the temptation to install a small wind turbine on a building:

• When wind hits a building, turbulence is created; such turbulence greatly interferes with power production.
• Building-mounted turbines can cause irritating vibration and noise.
• Studies have confirmed that most building-mounted turbines have produced far less electricity than predicted.

To learn more about the pros and cons of building-mounted turbines, see “The Folly of Building-Integrated Wind,” Environmental Building News, May 2009, and Mick Sagrillo's An open letter to inventors of vertical axis wind turbines and rooftop wind 'technology breakthroughs.’

The economics differ for off-grid homeowners
Some of the caveats listed above don’t apply to off-grid homeowners. Since those who live off the grid are accustomed to very expensive electricity, they are more likely than grid-connected users to put up with the high cost and maintenance burdens of a small wind turbine.

Off-grid homeowners lack access to the grid’s “infinite battery,” so it may make sense for them to install a PV array to cover most of their summer loads and a wind turbine to pick up the slack during the dark but windy winter months.

Last week’s blog: “Ten Ways to Improve a New Home.”