Total natural gas use for power generation in the United States was down 14% during the first seven months of 2013 compared to the same period in 2012, mostly because of higher natural gas prices relative to coal prices. High natural gas-fired generation in 2012 occurred as a result of the lowest spot natural gas prices in a decade—in fact, the two fuels contributed approximately equal shares of total generation in April 2012.

via Today in Energy http://www.eia.gov/todayinenergy/detail.cfm?id=13111