Our power company sends out a little newsletter/magazine and I found an interesting item on wind-power. For starters, it provides a whopping 0.1% of the energy used in America. It lists wood and water as providing the remainder of the 6.1% that is from renewable sources.
To give an idea of how much land would need to be dedicated to wind farms it gave this factoid. The city of Denver would require 1500 square miles of land to meet it's power requirement. And that is just Denver, not the metro area.