In addition, it is more difficult to properly synchronize wind’s fluctuating power flow with a system built for the steadier electric stream that fossil fuel plants tend to produce.

“As these wind turbines are built and interconnected, they’re interconnecting to local transmission lines, and for the most part they can produce electricity and inject it onto the system,” said Ellen Foley, a spokeswoman for the grid operator. “But there may be occasions where they may have to be backed down or curtailed because of the limitations of the line — it’s literally the size of the line.”

The fear, she said, is that a surge in energy could overload and shut down the wires, leading to a drop in voltage on the system that could spread blackouts through the region and to other parts of the country.

For the wind farm developers and operators, though, the curtailments can affect their bottom lines. David Hallquist, chief executive of Vermont Electric Cooperative, estimates that the curtailments will cost the cooperative $1.5 million in 2013. In New Hampshire, ISO New England allowed only about half of the potential power from the Granite Reliable Power wind farm into its system last year, leading the farm’s owner to temporarily withhold some of the payments it was supposed to make to Coos County, where it operates. David Blittersdorf, chief executive of AllEarth Renewables, which developed Georgia Mountain Community Wind in Vermont, said that at full operating capacity he can lose $1,000 an hour if the electricity is not sold.

“We have a grid system that’s not smart — it’s kind of dumb, it’s a 100-year-old system — and they run it like fossils and nukes are the only things that matter and the rest of us, they can fiddle with,” he said. Georgia Mountain is physically close to the Burlington market it serves, he said, and has never had issues with its connection to the grid. Still, he said, ISO New England reduced its output one night in January and never furnished an explanation. “They don’t care,” he said. “They don’t reimburse me.”

Cutting wind output can also interfere with the ability of utilities to meet state goals and mandates to include a certain percentage of renewable energy in the mix of power generated. In Vermont, the July wind curtailment caught the attention of Gov. Peter Shumlin, who wrote to ISO New England, questioning whether it was doing all it could to integrate and use renewable energy.

“Vermont has a clear preference for renewable resources and would have preferred that the local renewable energy produced by this utility-owned resource had been used,” Mr. Shumlin wrote. “I also urge ISO-NE to fully account for growing distributed generation renewable resources in its transmission planning assumptions; Vermont has seen a tremendous growth in these resources in the past few years and believes that growth will continue.”