The energy sector of Ohio consists of thousands of companies and cities representing the oil, natural gas, coal, solar, wind energy, fuel cell, biofuel, geothermal, hydroelectric, and other related industries. Oil and natural gas accounts for $3.1 billion annually in sales while ethanol generates $750 million. Toledo is a national hub in solar cell manufacturing, and the state has significant production of fuel cells. In 2008, the state led the country in alternative energy manufacturing according to Site Selection Magazine, while the natural gas industry has experienced growth due to the expansion of shale gas.