An offshore wind farm in the Nantucket Sound could save the New England region billions of dollars over 25 years, according to a new report.

The long-debated Cape Wind project, which would install 130 offshore wind turbines roughly five miles from the nearest shore, would be the first of its kind in the United States. It would cover 24 square miles in the sound.

The turbines would supply about 10 percent of the 2013 power demand in Southeastern Massachusetts and about 1 percent of the total 2013 New England demand.

The project would save the New England region about $185 million a year, according to the report, which was prepared this month by Charles River Associates and commissioned by backers of the project. Over 25 years, this would amount to $4.6 billion.

To do the analysis, Charles River used wholesale power costs, which are closely tied to retail costs paid by end customers. The savings were estimated by calculating wholesale power costs for the region with and without the Cape Wind project in place.

The report’s findings, however, did not dissuade the project’s skeptics, who said that while the project may be a good financial move, there are other important considerations.

“We would like to see them go back and do what the Fish and Wildlife Service asked and properly assess risks posed to birds,” said Sharon Young, field director of marine issues at the Humane Society of the United States.

Ms. Young emphasized that the Humane Society was not opposed to the project, but wants to see research on Cape Wind’s effects on waterfowl.

“The Humane Society strongly supports the need for alternative energy,” she said. “But as they say in real estate, it’s all about location, location location.”

In addition, Massachusetts Indian tribes have argued that the wind turbines would disturb spiritual rituals that require clear views across the sound.