Several factors can affect wind speed, and the ability of a turbine to generate more power. For example, wind speed increases as the height from the ground increases. If wind speed at 10 meters off the ground is six m/s, it will be about 7.5 m/s at a height of 50 meters. A 2003 Stanford University study examined wind speeds at higher elevations and found that as much as one quarter of the United States–including areas historically thought to have poor wind potential–is potentially suitable for providing affordable electric power from wind.[5] The rotors of the newest wind turbines can now reach heights up to 70 meters. In addition to height, the power in the wind varies with temperature and altitude, both of which affect the air density.
The more the wind blows, the more power will be produced by wind turbines. But, of course, the wind does not blow consistently all the time. The term used to describe this is "capacity factor," which is simply the amount of power a turbine actually produces over a period of time divided by the amount of power it could have produced if it had run at its full rated capacity over that time period.
