The U.S. needs a highly reliable electricity (or power) grid, which is depicted below.
The coal fleet plays a vital role in keeping the grid both reliable and resilient, so we can keep our lights on 24 hours a day, 7 days a week. A more reliable grid is one with fewer and shorter power interruptions. A resilient grid means a grid that is better prepared to recover from adverse events, like severe weather, or even worse problems that could have extreme consequences. For example, during extremely cold weather conditions (polar vortex) in 2013/14, coal-fueled power plants played a critical role in keeping the lights on in parts of the northeastern U.S.
Since 2010, a significant portion of the coal fleet has either closed or announced plans to close, raising questions about grid reliability and resilience.