While there is growing demand for large utility wind turbines across Rhode Island, the demand for small turbines is much less.

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But like its larger cousin, the small turbine needs good winds of at least 6 meters per second, or 13.4 mph. James Grasso, of Silent Sherpa, a Cranston energy advisory firm, found out the hard way.

In 2004, Grasso bought a 10-kilowatt turbine for $40,000. The state Office of Energy Resources paid half of the cost through the renewable-energy fund, which has since dramatically reduced the amount of such grants.

The turbine was set up on a hilly section of his family’s property in Exeter with the belief that it would pay for itself in seven years. The electricity the turbine produced wasn’t enough — about 200 to 300 kilowatt hours, Grasso said. The actual time of return would have been 30 to 40 years.

After keeping the turbine up for two winters, Grasso took it down and sold it in 2005.

“The decision was made [that] it wasn’t working as an investment,” he said. “It would have taken two generations to pay back.”

Utility turbines — the larger windmills being sought by some Rhode Island communities to offset energy costs — may be a good investment. But the smaller turbines erected by some homeowners can be risky.

The cost — generally $3,000 to $5,000 per kilowatt of generating capacity, according to the American Wind Energy Association — can be high and the payback long, and the small turbines generate far less electricity than the larger ones.

“The general rule of thumb is if you make it two times as big [it will produce] four times the amount of electricity,” said Henry duPont, managing director of Lorax Energy Systems, which installs wind turbines. “Small windmills live under that handicap, unfortunately.”

If the right tax credits and grants were in place, a small turbine could be paid off within 15 years, according to the American Wind Energy Association’s Web site. But in Rhode Island, some wind installers and residents say the current maximum reimbursement amount — $3,750 — is too low.

Homeowners, like the owners of larger turbines, can sell their unused electricity back to the utility company, but that can be another economic drain. Even at Portsmouth Abbey School, which has a 164-foot utility windmill generating about 40 percent of the school’s electricity needs, Brother Joseph Byron said that selling the excess energy produced by the school’s 660-kilowatt turbine has not been profitable.

Byron said the school pays 13 cents per kilowatt hour for retail electricity from National Grid, but only receives 5 cents per kilowatt hour from the utility company when selling back the extra electricity generated by the windmill. The benefit has been that the windmill offsets the school’s electricity needs.

But while there are setbacks, a small wind turbine can work — if the conditions are right.

On Block Island, where most residents rely on diesel to power electrical generators and electricity rates are two to three times those on the mainland — 35 to 42 cents per kilowatt hour — wind turbines can make sense. The strong winds are the best in the state.

Chris Warfel, president of Entech Engineering, said the island has seven operating residential windmills, ranging from 1 to 10 kilowatts, along with a 1-kilowatt turbine at the North Light lighthouse.

The historic Rose Island Lighthouse, just off Newport, also had wind turbine on site since 1993. Charlotte E. Johnson, executive director of the Rose Island Light House Foundation, called the new model that went up this year “a honey” because it produces most of the lighthouse’s electricity needs.

Block Island residents Verna and Everett Littlefield have had wind turbines next to their house since 1981.

Their first wind turbine, a Jacobs 10-kilowatt model, cost $22,000 to install. When it broke down in 1991 in the wake of Hurricane Bob, their insurance company paid for their second turbine, a Bergey 10-kilowatt model.

Verna Littlefield said that depending on wind speed, the windmill can cut their energy bill by half or more. In June, when her turbine was down for repairs, her energy bill was $200 for the month.

“I think it’s the only way to go. We are becoming more and more dependent on foreign oil to heat our house and provide our electricity,” Littlefield said. “We’ve got to do something about it. This was our way to do something about it, our little part.”

But not everyone on the island likes windmills.

One couple, Jonathan and Jo-An Evans, put up a 60-foot windmill on their property in the summer of 2000 as part of a U.S. Department of Energy program, said duPont, who installed the turbine. In 2004, the windmill was removed after neighbors sued the Evanses, claiming the turbine was too noisy.

“Noise impacts are very subjective,” duPont said. “If it’s your turbine, it sounds great. It sounds like you’re saving money. … If your neighbors hear it and it’s not benefiting them, it sounds like hell. There’s a big issue with perception.”

Personally, duPont was more fortunate with his own turbine. DuPont, a 25-year Block Island resident who is not hooked up to the electricity grid, has tried several different small turbines to power his home between 1983 and 2000.

In 2000, he installed the Bergey 10-kilowatt turbine that he still uses today. DuPont said the turbine, which cost $30,000, was a cheaper alternative to paying $50,000 for a power line.

He said he’s had few problems over the years. He’s changed the circuit boards after a lightning strike, and replaced the batteries that store the turbine’s output.

The strong ocean winds also power duPont’s electric car. “Instead of going to the gas pump, we go to the wind turbine,” he said with a laugh.

The Web site for the American Wind Energy Association is www.awea.org

mlee@pressofac.com