How clean energy and efficiency can replace coal for a reliable, modern electricity grid

Aging coal-fired power plants are retiring all over the country, presenting the U.S. with an exciting opportunity to lead a global transition to a clean energy economy. The move away from coal begs the question: What will replace it? Energy efficiency, renewable energy and electric grid modernization should play an important part in replacing retiring coal capacity, and thereby mitigate the rush to build new natural gas plants.