Coal plants are being shuttered because they are inefficient and much more expensive to replace than the modern combined cycle NG plants. With gas fired power plants the thermal energy gets recycled to boost efficiencies. Another big feature of the NG plants is they can ramp up almost instantly. So when extreme hot weather overloads the grid with AC loads, the NG plants are online right away, and ramp off quickly also. Some would suggest the extreme warm weather the nation is seeing is caused by the dirty coal plants worldwide, so maybe there are two wins in shuttering inefficient coal plants? Electricity will be generated with the least expensive options first, hydro, nuke, coal, then NG. But with all the fracking and NG glut to the point where we are exporting it, NG could be the bridge energy until a better, cleaner, faster fuel comes online. It's not just the EPA, it's the arithmetic.