As the need for electricity to power the nation’s digital economy grows, coal is no longer playing a primary role, and that’s problematic, because it undergirds the electric grid and is the most reliable source of energy.

Without coal plants that supply base-load power on demand, large parts of the United States, from the mountain states to the mid-Atlantic and southeast, will become more vulnerable to power shortages and increases in electricity costs. With the loss of more than 600 coal units in less than 10 years, coal’s share of the nation’s electricity generating capacity has dropped from almost half in 2007 to 30 percent today, and it’s expected to fall even further.