WASHINGTON — In the U.S. Department of Energy report on the nation’s energy market and reliability, increased use of natural gas plants is the primary reason listed for the retirement of coal power plants in the United States.

The Energy Department released its findings Wednesday as the result of an April 14 request by Secretary of Energy Rick Perry. The report stated the growth of natural gas availability, more-efficient plants and lower production costs from methods such as hydraulic fracturing caused natural gas electricity prices to decline, making it a better option instead of coal and nuclear power

“Production costs of coal and nuclear plants remained somewhat flat,” the report said, “while the new and existing, more flexible, and relatively lower-operating cost natural gas plants drove down wholesale market prices to the point that some formerly profitable nuclear and coal facilities began operating at a loss.”

The 187-page study also noted a national low growth in electricity demand, environmental regulations and additional electricity sources in solar and wind facilities.

According to U.S. Energy Information Administration, “electricity demand historically had risen with economic growth,” but the trends split around 2000 because of multiple factors, including energy efficiency programs and standards, improvements in technology and slow population growth.

As for regulations, the report said the implementation of regulations between 2011 and 2021 are the result of statutes passed from 1970 to 1990.

“Due to low natural gas prices and abundant natural gas generation capacity additions, most of the coal plants that retired between 2011 and 2015 (when the environmental regulations took effect) had not been operating in their intended baseload fashion for several years,” the report noted.

According to the report, the average coal plant fleet was built in “the mid to late 1970s,” and no new facilities have been built since 2014 because of higher costs compared to natural gas-fired plants. Most of the plant retirements were in regions the Energy Department labels as California, the Midwest, Southeast and mid-Atlantic. The latter area includes West Virginia.

The report additionally mentioned increased coal mining in states such as Wyoming, which has surface mines.

“Between 2011 and September 2016, increased mechanization and a shift to western coal resulted in a loss of 36,000 coal mining jobs, of which nearly 90 percent were in Appalachia,” the study said. “Growth in some energy sectors, such as solar energy deployment, supported new jobs, but they vary regionally and often do not correlate well with concurrent job losses in sectors such as coal mining or power plant operations.”

Coal power plants generated 61 percent of electricity in the mid-Atlantic region in 2002, yet by 2016, that number shrunk to 34 percent. Electricity from natural gas facilities increased from 5 percent to 26 percent in the same period.

The study recommends as part of infrastructure development to encourage the U.S. Environmental Protection Agency to allow coal-fired plants to improve efficiency without “triggering new regulatory approvals” as well as related costs.

Part of the Marcellus and Utica shale formations lies below West Virginia, with the shale going from central West Virginia to southern New York.