What is the Affordable Clean Energy rule and how does it compare to the Clean Power Plan?

What is the Affordable Clean Energy rule and how does it compare to the Clean Power Plan?

On August 20, Acting Environmental  Protection Agency (EPA) Administrator Wheeler signed a notice of proposed rulemaking called the Affordable Clean Energy (ACE) rule, the next step in developing the Trump Administration’s much-anticipated replacement to the Obama-era Clean Power Plan.
The Affordable Clean Energy rule establishes guidelines for states to develop carbon emissions reductions standards for existing coal-fired power plants.