Wind turbines: inside and outWind turbines depend on wind speed to produce energy. At the ideal wind speed, a wind turbine like this one in Roscoe, Texas, can produce the electricity needed by nearly 500 typical American homes. A turbine takes one day to erect and costs $2 million. The Department of Energy's goal is to obtain 6 percent of U.S. electricity from wind by 2020.
Sources: The American Wind Energy Association, Energy Information Association, Danish Wind Industry Association, Mitsubishi Power Systems, Peak Wind.
Graphic by Monica Ulmanu.