Power plant emissions result from the combustion of fossil fuels such as coal, gas, and oil. These emissions include sulfur dioxide (SO₂), nitrogen oxides (NO_x), particulate matter, and hazardous air pollutants, all of which are subject to environmental regulations. Another emission is carbon dioxide (CO₂), suspected of being responsible for global warming.

Historically, under both federal and state regulations, the demand for gas to heat homes and to meet needs of business and industry took priority over utility use to generate electricity. These restrictions have been eased by amendments to the Fuel Use Act in 1987, and, as a result, new gas-fired generation units are being constructed. However, coal-fired units continue to provide over 50 percent of the total utility generation of electricity.

Until the late 1960s, a typical electric utility scenario was one of steadily growing electricity demand, lower costs of new...