Coal stockpiles at coal-fired power plants fell to 144 million tons in August, the lowest monthly level since late 2014, according to the U.S. Energy Information Administration. The stockpiles usually follow a seasonal pattern as electricity demand rises and falls, and they typically reach their lowest point in August.
Coal consumption is usually higher in the summer and winter and lower in the spring and fall. Between January and August, coal plants received an average of 53,000 tons of coal monthly and consumed 56,000 tons per month, according to the EIA. The amount of coal the plants receive is less variable than how much they consume “because producing mines and coal transporters (mainly railroads) generally require power plants to receive coal at a roughly constant rate during the year.”
As of August, 57% of coal-fired generating capacity had a stockpile that would last more than 60 days, according to the EIA. About 33% of capacity had a stockpile that would last between 30 and 60 days, and the remaining 10% had a stockpile that would last less than 30 days.
Nearly 55% of coal stocks were subbituminous coal, which is mostly produced in Wyoming. “On average, coal plants using subbituminous coal can operate about 80 days at August 2017 stockpile levels,” according to the EIA. “Another 42% of coal stocks are bituminous coal from states such as West Virginia, Kentucky and Pennsylvania. Plants using bituminous coal can operate about 90 days at August 2017 stockpile levels.” Coal stockpile data at individual plants are confidential.