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Today in Energy

August 5, 2020

More than 100 coal-fired plants have been replaced or converted to natural gas since 2011

U.S. coal-to-natural gas plant conversion type and capacity
Source: U.S. Energy Information Administration, Annual Electric Generator Report and Preliminary Monthly Electric Generator Inventory

According to data from the U.S. Energy Information Administration (EIA), 121 U.S. coal-fired power plants were repurposed to burn other types of fuels between 2011 and 2019, 103 of which were converted to or replaced by natural gas-fired plants. At the end of 2010, 316.8 gigawatts (GW) of coal-fired capacity existed in the United States, but by the end of 2019, 49.2 GW of that amount was retired, 14.3 GW had the boiler converted to burn natural gas, and 15.3 GW was replaced with natural gas combined cycle. The decision for plants to switch from coal to natural gas was driven by stricter emission standards, low natural gas prices, and more efficient new natural gas turbine technology.

Two different methods are used to switch coal-fired plants to natural gas. The first method is to retire the coal-fired plant and replace it with a new natural gas-fired combined-cycle (NGCC) plant. The second method is to convert the boiler of a coal-fired steam plant to burn other types of fuel, such as natural gas.

Between 2011 and 2019, owners of 17 coal-fired plants adopted the first method, replacing old coal-fired power plants with new NGCC plants. The new NGCC plants have a total generating capacity of 15.3 GW, 94% more than the 7.9 GW capacity of the coal-fired power plants they replaced. The increase in capacity is largely a result of the advanced turbine technology installed in NGCC plants.

U.S. coal-fired capacity retired or repurposed to natural gas by conversion type
Source: U.S. Energy Information Administration, Annual Electric Generator Report and Preliminary Monthly Electric Generator Inventory

During this time period, 104 coal-fired plants adopted the second approach, converting the steam boiler to burn other fuels, most commonly natural gas, although some were configured to burn petroleum coke (a refinery by-product), waste materials from paper and pulp production, or wood waste solids.

Coal-fired plants in the eastern half of the country have been good candidates for conversion because they tend to be smaller-capacity units and are mostly over 50 years old. Of the 104 coal-fired plants in this age range, 86 have converted their boilers to burn natural gas, representing 14.3 GW of capacity. Although most transitioned entirely to natural gas, a few maintained coal-burning capabilities, allowing them to burn whichever fuel is most economically efficient.

The utility with the most conversions between 2011 and 2019 was Alabama Power Co., which converted 10 generators located at four coal plants in Alabama, totaling 1.9 GW of capacity. These conversions took place between 2015 and 2016, largely to comply with the Mercury and Air Toxics Standards (MATS) required by the U.S. Environmental Protection Agency.

As the U.S. coal-fired electric generation fleet continues to manage challenges from emission standards and low prices for natural gas, EIA expects more of these conversions to take place in the future, particularly in the Midwest and Southeast. EIA has been notified of eight planned NGCC projects, five of which are currently under construction, which will replace existing coal plants.

Principal contributor: Lindsay Aramayo