U.S. Power Production
Coal is the most prevalent fuel used in generating electricity in the United States: 40% of U.S. generation capacity is coal. Coal plants run nearly continuously (they don't start and stop quickly), and they run on relatively inexpensive fuel, so they are considered "base load" plants, and actually produce 56% of the nation's output of electric energy. Gas power plants can be turned on and off quickly, but the fuel is more expensive, so they are generally used for "peak" loads, when the demand is high. Because turbines with water flowing through them can be brought on- or off-line quickly, hydroelectricity is also often used to supply peak loads. Some hydroelectricity is also considered base load: In most major river systems some water is always flowing through some of the turbines. In capacity calculations, hydroelectricity is complex, since hydropower dams are part of a river system, and the same water is often used more than once, flowing through turbines in multiple dams to generate electricity. Releases of water not only impact downstream power capacity but also downstream environmental issues.
In 1978, Congress prohibited the use of natural gas as a fuel to generate electricity (except for peaking units), as it was known that natural gas production was not increasing, and natural gas is used to heat half of U.S. homes. Congress repealed this ban in 1987. More stringent environmental standards and longer permitting times have discouraged the burning of coal (which produces more air pollution than natural gas). As a result, there has been a significant increase in natural gas generation of electricity. Most new electrical capacity is predicted to be gas-driven, even though U.S. production of natural gas has remained stagnant. Natural gas prices have therefore increased, and natural gas imports are increasing.
Renewable energy use is also on the rise. Many states are mandating additional uses of renewable energy, especially wind energy. Federal mandates have also been under consideration by the U.S. Congress. New sources of renewable generation include wind, solar, landfill gas, geothermal and biomass power production.
Recent information on the electric power generation mix in your area can be found under Electricity Generation on DOE's Energy Information Agency Web site.