With higher altitudes, wind flows more freely, and speeds typically increase. High altitudes and water locations have less friction from objects on the Earth's surface, such as trees, mountains and buildings. This is why offshore turbines generate more electricity, even at shorter heights.
For onshore wind turbines, areas with higher-than-average wind shear -- the change in wind speed with altitude -- are ideal for wind farms. According to Berkeley Lab's "Land-Based Wind Market Report: 2024 Edition," most wind turbine towers taller than 110 meters are concentrated in the Midwest and Northeast U.S. because they have higher wind shear.
Wind turbines do not have a large footprint on the ground, but they take up significant airspace. According to the University of Michigan's Center for Sustainable Systems wind energy factsheet, the direct land use of a wind turbine in the U.S. is 85 acres (0.13 square miles) per MW of installed capacity, with the tower pad and access roads occupying 1% of the area. This means a 2-3 MW wind turbine occupies 170 to 255 acres (0.27 to 0.40 square miles) of land.
A larger challenge is installing multiple turbines. A wind farm needs considerable space between the turbines to minimize turbulence, follow natural land contours and avoid other obstacles. A single turbine should be spaced approximately seven rotor diameters away from another wind turbine. This spacing protects the turbine and nearby structures from turbulence, and it enables the turbine to work optimally.
According to the U.S. Department of Energy, the average rotor diameter of a modern wind turbine is 133.8 meters (438.98 feet). That means the amount of airspace between turbines should be 936.6 meters (3,072.83 feet), or 0.58 miles. Much of the indirect land under the turbines can be used for other purposes, like agricultural farms and ranching. Many existing wind farms are in agricultural areas in the Midwest U.S.