Renewable energy use grew an average of 5 percent per year over 2001-2014 from its most recent low in 2001. The increase over the past 14 years was in part because of growing use of wind, solar, and biofuels. Wind energy grew from 70 trillion BTU in 2001 to more than 1,700 trillion BTU in 2014. During the same period, solar energy (solar thermal and photovoltaic) grew from 64 trillion BTU to 427 trillion BTU, and the use of biomass for the production of biofuels grew from 253 trillion BTU to 2,068 trillion BTU. Hydroelectricity was the largest source of renewable energy in 2014, but hydro consumption has decreased from higher levels in the mid-to-late 1990s. Wood remained the second-largest renewable energy source, with recent growth driven in part by demand for wood pellets.
About 13 percent of the renewable energy used in the United States is now consumed in the transportation sector, which experienced the largest percentage growth in renewable consumption from 2001 to 2014. The growing demand for liquid biofuels, including both ethanol and biodiesel, pushed renewables to nearly 5 percent of the sector's energy consumption in 2014.
