Dong has plenty of company. Statoil, the Norwegian fossil-fuel giant, has been aiming to get into the offshore business in the United States for years, and proposed in 2011 to build a farm off the Maine coast using floating platforms it had designed. The company withdrew the project two years later amid uncertainty over changing state policies, eventually deciding to build off the Scottish coast.

Now it is back, having won a 33-round auction to secure a 79,000-acre site south of Jones Beach on Long Island. Statoil beat out several other bidders, including the state’s energy agency, Dong and a subsidiary of Iberdrola, a leading energy company based in Spain. Statoil pledged $42.5 million for the lease, which still awaits final approval from the Bureau of Ocean Energy Management, far more than the $16 million generated by all earlier offshore wind auctions combined.

“There’s a lot of companies starting to invest that had been wary of the U.S. offshore wind market and some of the initial lease sales,” said Walter Cruickshank, acting director of the Bureau of Ocean Energy Management. “They have been coming to the table in a big way more recently.”

The appeal of offshore winds as an energy source goes beyond their potential role in efforts to slow global warming. As people flock to coastal cities, where land is scarce and expensive, and conventional power plants are moving toward retirement, states have looked to add new forms of power production. Moving it out to sea has become more attractive, proponents say.

The country’s coasts, home to over half the population, offer some of the strongest wind resources in the world, creating, in theory, enough energy to provide roughly four times the power the nation now produces.

Though it is easier and cheaper to construct turbines on land, the East Coast in particular offers opportunity because of its strong winds and shallow waters, which means turbines can operate farther out to sea, and out of sight. The potential of offshore wind power converged with rising demand on Long Island’s South Fork, where in areas like the Hamptons, commercial activity was rising and property owners were building larger houses, calling for more air-conditioning and more pool pumps.