The Fuels That Keep Your Lights On

Coal dominates the mix of fuels used to generate our electricity. But recent figures show that coal’s share of that mix for the U.S. has fallen below 50 percent.

Coal passed that symbolic threshold because natural gas is replacing some of the work coal has done generating electricity. Since 2005, natural gas use has increased from 19 percent to 25 percent. During that same period, coal use fell from 50 percent to 42 percent.

The ability of a particular fuel to produce a lot or a little electricity is called its “energy density.” Two fossil fuels, natural gas and coal, have good levels of energy density and are still a major part of the national mix.

Utilities also consider two other closely related factors in the mix: fuel cost and available technology. A fuel’s cost includes more than its price per cubic foot or per ton. Each kind of fuel has different operating costs. Costs include technology to meet environmental and safety standards, as well as how easy or difficult it is to obtain a steady supply of the fuel.

The shift is not uniform throughout the United States. What’s sensible in one region may not be an economical choice in another region. Kentucky has a plentiful local supply of coal and the mix of fuels is not changing rapidly. Natural gas provides only 2 percent of Kentucky’s electricity. Within the next few years, the shift away from coal and toward more natural gas at the national level is expected to continue.