Can the continental United States make a rapid, reliable and low-cost transition to an energy system that relies almost exclusively on wind, solar and hydroelectric power? While there is growing excitement for this vision, a new study in the Proceedings of the National Academy of Sciences (PNAS) by 21 of the nation’s leading energy experts, including David G. Victor and George R. Tynan from the University of California San Diego, describes a more complicated reality. These researchers argue that achieving net-zero carbon emissions requires the incorporation of a much broader suite of energy sources and approaches.