Arkansas produced 588,700,000,000,000 British thermal units (1.725×1011 kWh) in 2007, mostly from coal, petroleum, nuclear, and renewable energy sources.[18] In 2007, 46.2% of Arkansas's energy production was from natural gas, 27.6% from nuclear power, 19.9% from renewable sources, 6.2% from fossil fuels.[19] Arkansas imports petroleum for use in the transportation sector but is a net exporter of electric power, selling 20,400,000,000,000 British thermal units (6.0×109 kWh) to the national electric grid in 2007.[20] The rural nature of Arkansas causes Arkansans to spend more on energy than the national average. Due to transmission, 65% of electricity was lost on its way to consumers in 2007.[21] The state's low population density results in higher electricity costs and more gallons of fuel used per vehicle.[22] Arkansas consumes more natural gas and renewable energy and less fossil fuels than the national average.[23]