The generation of electricity by the use of wind turbines is growing rapidly, as indicated by Tim Wheeler's story on the Massachusetts Cape Wind project and what it might mean for wind projects off the coast of Maryland.
As the graph below shows, U.S. wind generation capacity grew from less than 2,000 megawatts in 2003 to 8,000 in 2008. (These figures are from the American Wind Energy Association.) Figures for wind capacity vary by source, perhaps because the notion of "capacity" for generators that depend on highly variable and uncertain wind currents is a moving target. But in any case the trend is clear. The chart below will have much higher bars for 2009 and 2010 once the data are plugged in.
But whatever the figures, wind energy is still relatively scarce. Total U.S. generation capacity is about 1 million megawatts. And wind power is still very expensive, although the cost is coming down thanks to the economies that usually accrue to maturing technology, scaling-up of production and so forth. A large factor driving the construction and use of wind capacity is large government subsidies. The Union of Concerned Scientists gives a good summary.