This is a nice map of the wind resource for 80m = 260ft hub height wind turbines. It covers the USA including coastal resources where off shore turbines may be considered. For perspective, the new GE Turbine has a maximum hub height of 139m = 455ft. The kingston turbine which my NE friends will be familiar with has a hub height of 80m. See resource map here Again for perspective, the Kingston turbine, which is deemed to be economical, is in a region with wind speeds in the neighborhood of 6.5 m/s. A little off shore and in the Great Plains you see vast areas that are at about 8.5 m/s. A turbine produces twice as much power in 8.5 m/s wind as it does in 6.5 m/s wind. This is because power in the wind goes as the cube of wind speed. So the potential in these areas is more than 100% higher than where the already economical Kingston turbine is located. What is the practicality of offshore wind? Page 8 of This European Wind Energy Agency report shows that, as of 2011, Europe is routinely building wind farms in nearly 30 m = 100ft of water and Germany has a wind farm in over 40m = 130 ft of water. Vast tracts of land off of the East Coast of the US have great resource and have water depths of less than 100 feet. Google Earth now includes water depths of the ocean so you can easily see for yourself. From EWEA report linked to above.
Global Resource Maps Here .