Ethanol fuel is produced in the state, and consumer gasoline is required to contain 10% ethanol (E10). As of 2006, Minnesota is the only U.S. state with such a mandate. 20% ethanol (E20) will be mandated in 2013. Minnesota has the highest number of fuel stations offering E85 fuel, with 300 statewide. A 2% biodiesel blend has also been required in diesel fuel since 2005. Electricity-producing wind turbines have become popular, particularly in the windy southwest region on the Buffalo Ridge. As of November 2006, the state is the country's fourth-largest producer of wind power, with 812 megawatts installed and another 82 megawatts planned.