(Bloomberg) -- New York will need to tap offshore wind, one of the most expensive sources of electricity, to meet its clean energy goals, according to the state’s chairman of energy and finance.

“We are not going to achieve our 50% goals by 2030 without offshore wind,” said Richard Kauffman, the former chairman of Levi Strauss & Co. who was appointed by Governor Andrew Cuomo to revamp New York’s energy system.

Developers have proposed wind farms off the coast of Long Island, which could deliver power to New York City without requiring new long-distance transmission lines. That gives offshore wind an advantage over big solar projects or onshore wind farms, which could be built in upstate locations that aren’t close to existing transmission cables, Kauffman said in an interview Tuesday at the Bloomberg New Energy Finance summit in New York.

Developers have pushed for years to build wind farms along the U.S. coast, and have been stymied by costs, which are roughly twice as high as installing turbines on land. Unlike Europe, where offshore wind has thrived under government subsidies, U.S. projects have stalled as utilities refused to pay a premium for the power.

Falling Costs

Building costs, however, are projected to fall. A study released last month by the University of Delaware found costs for offshore wind farms may decline as much as 55 percent by 2030. The U.S. government has designated a 127-square-mile building site in the Atlantic, 12 miles south of Long Island.

New York will outline its plans for offshore wind in the coming months, Kauffman said. The state’s long-term energy plan will require utilities to buy clean power. “It is not going to have offshore wind as a particular carve-out,” he said.