Horse Hollow Wind Energy Center in Taylor and Nolan Counties, Tex.

About 100 miles (160 kilometers) west of Dallas, 47,000 acres (19,000 hectares) of Texas cedar and scrub oak have been given over to the 421 wind turbines that comprise the Horse Hollow Wind Energy Center. The 291 1.5-megawatt turbines built by GE and the 130 2.3-megawatt wind turbines built by Siemens together deliver 735 megawatts of peak power. The farm was completed in 2006 and is operated by NextEra Energy, a subsidiary of Florida Power & Light, which operates wind facilities that deliver over four gigawatts of power across the U.S.

Horse Hollow won't retain the crown for long, however: By the middle of 2009, E.ON Climate and Renewables will complete the fourth phase of the Roscoe Wind Farm in Texas, which will deliver 781.5 megawatts from 627 turbines.

Other giant wind farms that have been announced include the Shepherd's Flat Wind Farm in Oregon (800 megawatts, 303 wind turbines) and a wind farm in Markbygden, Sweden, (four gigawatts, 1,101 wind turbines).