We obtained one or more categories of land-use data for 172 individual projects, representing 26,462 MW of proposed or installed capacity. Of this capacity, 19,834 MW was completed as of March 2009, 2,892 MW was under construction, and the remainder consists of proposed projects. According to a the American Wind Energy Association (2009b), as of March 2009, 28,206 MW wind capacity had been completed in the United States, with 24,640 MW meeting our criteria as a large modern plant with a capacity of at least 20 MW and constructed after 2000. As a result, we collected at least some information on about 80% of the targeted installed wind capacity in the United States. …
Based on the collected data, direct impact is mostly caused by road development, as opposed to the turbine pads and electrical support equipment. For 93 projects representing about 14 GW of proposed or installed capacity, the average permanent direct impact value reported was 0.3 ± 0.3 hectare/MW of capacity (0.74 acre/MW). Fewer projects (52 representing 9 GW of capacity) provide temporary direct impact data, with an overall average of 0.7 ± 0.6 hectare/MW of capacity (1.73 acre/MW). This implies a total direct impact area (both temporary and permanently disturbed land) of about 1 ± 0.7 hectare/MW (2.5 acres/MW), but with a wide variation in this area.
We also found reported total-area data for 161 projects representing about 25 GW of proposed or installed capacity. Excluding several outliers, the average value for the total project area was about 34.5 ± 22.4 hectares/MW (85 acres/MW), equal to a capacity density of 3.0 ± 1.7 MW/km².
Technical Report: NREL/TP-6A2-45834, August 2009