Offshore wind power so-far is a very British thing. In the offshore wind race, Team GB has more than half-of-the medals, since the UK has installed 2,500 megawatts of the world's 4,600 megawatts, according to the Earth Policy Institute. See http://www.earth-policy.org/plan_b_updates/2012/update106. By comparison, global land based wind was about 233,500 megawatts at the end of 2011.
First deployed in 1991 in Denmark, wind is now operating in the waters of 12 nations, and its capacity has increased 6-times since 2006. Of course, the rapid increase reflects the very small base from which it is growing.
The principal barrier to offshore wind development is cost and not the wind resource. Ocean winds are among the best in the world, but costs for capturing that wind remain much greater than land wind farms. Offshore wind in the USA costs about 18 to 22 cents per kilowatt-hour, when wind on land can be produced for 5 cents per kilowatt-hour.
Will the US begin producing offshore wind? Major challenges to offshore wind development exist here, when compared to Europe or Asia. Though Hawaii is an exception, many parts of the coastal USA have lower electricity prices than found around the world and have access to large, substantially lower priced land wind resources. Siting wind on land in the geographically small, heavily populated UK is much more difficult than doing so in Texas, Oregon, California, Washington, New York, all of which have good on-land wind resources. The case for building offshore wind is much more difficult to make when land-based wind can be developed and a lower cost.
Despite the obstacles, at least three offshore US wind projects are in serious stages of development--the Cape Wind project in Massachusetts, a Rhode Island proposed project, and a wind farm off New Jersey. Perhaps one of these three projects will become America's first, but offshore wind will face an uphill climb in the USA for many years to come, unless its costs fall considerably.