The U.S. depends on fossil fuels for much of the production of electricity. Coal and Natural Gas are the two major sources of power generation followed by Nuclear power.
Shale gas is slowly eroding the consumption of coal. For example, since 2007 the use of coal in power production has been declining. The U.S. is still the second largest coal market in the world and consumed 832 Mt (metric tons) in 2014. The decline in crude oil prices is also allowing companies to switch to natural gas thus further reducing the dependence of coal as a fuel source. The use of coal for electricity generation fell from 50% in 2008 to 38.7% in 2014 and is projected to dip further, according to the EIA.
The following chart the sources of electricity production in the U.S.:
Click to enlarge
Source: US Coal Exports:The Long Road to Asian Markets, The Oxford Institute for Energy Studies, University of Oxford