Strict regulations to limit the toxic air emissions from coal-fired plants in the United States are working. Many utilities striving to meet these tighter standards are finding they can’t afford the high costs of upgrades and retrofits to their aging facilities. Instead, they are retiring these plants and turning to other, cleaner sources of power.

One such utility is South Carolina Electric and Gas (SCE&G). A subsidiary of the Cayce, S.C.-based SCANA Corp., it recently announced that it plans to retire up to six coal-fired generating units at three of its facilities. The plants will be retired by the end of 2018.

SCE&G made the announcement as part of its annual Integrated Resource Plan filed at the end of May with the Public Service Commission of South Carolina. The company noted that it has spent more than $600 million on improvements at its largest coal-fired facilities to comply with tighter Environmental Protection Agency emission standards. As a result, those facilities have seen reductions of more than 90 percent in the emissions of such pollutants as sulfur dioxide, nitrogen oxides and mercury.

Tests at other facilities produced much lower reductions, and the company decided that it could not afford the modifications it would need to make to keep them in operation. These units at the company’s Canadys, Urquhart and McMeekin facilities range in age from 45 to 57 years.

The company intends to retire these aging, coal-fired plants and replace them with natural gas-burning units. As a result of this transition, the company projects it will generate 615 kilowatt-hours (kWh) more power with natural gas and 679 million kWh less with coal over the next five years.

At the same time, SCE&G announced it will also be expanding its generation of nuclear power. In March, the U.S. Nuclear Regulatory Commission issued the company a combined license to construct and operate two new nuclear power units at its V.C. Summer Nuclear Station. Each of the new units will have a generating capacity of 1,117 MW.