“For decades, coal has been the dominant energy source for generating electricity in the United States. EIA’s Short-Term Energy Outlook (STEO) is now forecasting that 2016 will be the first year that natural gas-fired generation exceeds coal generation in the United States on an annual basis. Natural gas generation first surpassed coal generation on a monthly basis in April 2015, and the generation shares for coal and natural gas were nearly identical in 2015, each providing about one-third of all electricity generation. The mix of fuels used for electricity generation has evolved over time. The recent decline in the generation share of coal, and the concurrent rise in the share of natural gas, was mainly a market-driven response to lower natural gas prices that have made natural gas generation more economically attractive. Between 2000 and 2008, coal was significantly less expensive than natural gas, and coal supplied about 50% of total U.S. generation. However, beginning in 2009, the gap between coal and natural gas prices narrowed, as large amounts of natural gas produced from shale formations changed the balance between supply and demand in U.S. natural gas markets.”