The Interior Department just issued a new report on offshore energy potential, noting that there's technically enough wind potential off the coasts to supply enough electricity for the entire United States. Of course, that's assuming these offshore wind projects can ever get approved—just witness the wrangling that's held up Cape Wind for the past eight years. (The Interior Department's expected to make a decision on that soon—presumably it will get approved, which should open the gates for other offshore projects.)

So how easy is it to harvest all that potential? For now, the easiest places to stick wind turbines are in the relatively shallow waters off the coast—taking advantage of all those sites could provide some 20 percent of the electricity demand for coastal states. Since coastal states include most of the big ones—Texas, California, New York, and so on—that's about 16 percent of the nation's electricity needs. Not bad. But offshore wind is still costly. Prices for the turbines themselves are tumbling down, but you also need to factor in platforms to hold the turbines up, undersea transmission lines, and higher maintenance costs. Over at The Wall Street Journal, Keith Johnson points out that oil companies might be able to pitch in here—they have a lot of expertise with offshore platforms—but it's not always a no-brainer investment, especially as long as there's no price on carbon.

Ironically, as Johnson notes, the most promising resources could be those much, much further offshore. The main challenges are engineering, since no one's quite perfected a technique for getting platforms to stay stable that far out in choppy waters, but since the wind further offshore is a great deal stronger and steadier, the economics make a lot more sense once those technical hurdles can be cleared.

(Flickr photo credit: Tiger Hobbes)

--Bradford Plumer