The first wind turbines to be installed off the coasts of the United States were constructed over the past few days about three miles offshore of Block Island, Rhode Island.
While wind farms have been built all over the U.S. on land, the market for building wind farms in U.S. waters has stalled thanks to legal threats, lack of regulatory support, and push back from coastal property owners. At the same time, the “offshore wind” industry has boomed throughout Europe.
The construction milestone is an indicator that offshore wind is finally becoming a reality in the U.S. after many years of fits and starts, and could one day provide substantial amounts of clean energy to Americans.
Last Tuesday, clean energy developer Deepwater Wind began installing the first wind turbine on top of the towers at its Block Island Wind Farm. By Wednesday night, the company had put in the first turbine blade. By Thursday, the first wind turbine had been completed.
Construction on the wind farm, which is using gear from GE (GE) among others, started about a year ago. When completed later this year, the farm is supposed to provide about 30 megawatts of energy, a relatively small amount compared to what natural gas and coal plants, or even large-scale solar farms, can generate.
However, what the Block Island Wind Farm lacks in size, it makes up for in timing. Multiple offshore wind projects have been planned for the eastern seaboard for years, but many have stalled.
The poster child for the lagging offshore U.S. wind industry is Cape Wind, a once planned $2.6 billion project to install wind turbines across 24 square miles off the coast of Nantucket. After years of legal battles, including from residents that didn’t want their views spoiled by turbines, the companies that had committed to buy the energy from Cape Wind backed out.
For more on the economics of clean energy, watch:
The Block Island Wind Farm is the first of about a dozen planned offshore wind projects in U.S. waters and represents growing support for the clean energy option.
Last week, the Massachusetts legislature passed an energy bill that includes the largest state commitment to offshore wind in the U.S. to date. Under the law, which the state’s Governor still needs to sign, utilities would have to buy a combined 1.6 gigawatts of electricity from offshore wind farms in a little over a decade.
Massachusetts is home to waters that have some of the biggest potential for U.S. offshore wind. In addition to the Cape Wind project, DeepWater Wind and Danish energy company Dong Energy hold leases off the state’s coast.
Get Data Sheet, Fortune’s technology newsletter.
Dong Energy is the world’s largest offshore wind developer. The company, which is partly owned by the Danish government and Goldman Sachs, went public in June, largely based off of the success of the offshore wind industry in Europe.
In Europe, over 11 gigawatts of energy are being produced by offshore wind farms. There are 84 offshore wind farms either operating or under construction in the seas around 11 countries in the continent. Dong Energy plans to build the world’s largest offshore wind farm, called the Hornsea project, off the coast of Yorkshire in Northeast England.
One of the reasons offshore wind hasn’t taken off in the U.S. is because the costs of building the first projects, and thus producing the first energy, have been high. The energy from the Block Island Wind Farm has an initial contract of 24.4 cents per kilowatt-hour, which is about 10 cents more than Rhode Island residents currently pay for their electricity, according to Scientific American.
However, prices for offshore wind in Europe have dropped significantly, and they can expect to do so in the U.S., too, as more projects come online. According to the International Renewable Energy Agency, offshore wind could cost on average 12 cents per kilowatt hour by 2025.
Dong Energy recently won a contract to produce offshore wind off the coast of the Netherlands for eight cents per kilowatt hour. At that price, the power is competitive with fossil fuel-based energy.
