Energy experts are at war over a radical assertion that by mid-century the United States will be able to meet all its energy needs with wind, solar and hydro power. The claim was made in 2015 by four academic researchers , led by Mark Z. Jacobson, for the continental United States, and it asserts that those renewables will replace not just the coal and natural gas used to make electricity, but also the gasoline and diesel that run cars and trucks, and the gas used in home heating. The paper is regularly cited by environmentalists who claim that the current fleet of U.S. nuclear reactors could close without any consequences to grid reliability. But last week, a group of prominent researchers, some from Stanford and UC-Berkeley, and others from the National Oceanographic and Atmospheric Administration, Carnegie Mellon and other mainstream organizations, published a second paper that said that while they support the expanded use of renewables, Professor Jacobson et al. were dreaming.