Meeting EPA demands for clean air is a costly process. Then comes the balance between tearing down the plant or is it profitable to change to natural gas. All of things have to be considered. Also with properly installed scrubbers and injectors for CO2 waste. All factors come into play. Then comes the electrical grid and it’s supply and demand. We need prime power plants to maintain the grid. Solar or wind can not restore the power grid. It requires prime power plants.