Some power plants pollute more than others. The US has enacted regulations that require them to clean up or shut down. Within the next ten years tens of thousands of megawatts worth of power plants will be shut down, possibly 12,300 megawatts in 2015 alone, as the regulations are enacted. The energy impact is not expected to be as great as originally feared because Americans are consuming less and using renewable sources more. The pollution impact will be greater, because these are the worst coal polluters. As energy use changes, inefficient operations can be shut down, improving the air for all.