Scores of new coal-fired power plants that were being planned across the nation six or seven years ago have mostly been shelved. Last year alone, utilities and power-generating companies dropped plans to build 38 coal plants, according to the Sierra Club, while announcing they would retire 48 aging, inefficient ones. Stepping into the void is natural gas and renewables. Utilities have also more aggressively embraced demand-side management strategies to bend down the growth curve.