The U.S. Department of Energy has just published (on Sept. 17) the mix of energy sources to generate U.S. electricity: coal, 49.5 percent; nuclear, 19.6 percent; natural gas, 19.2 percent; oil, 1.8 percent; hydro, 7.1 percent. Collectively, biomass, solar, wind and geothermal contribute less than 1 percent each for a total contribution of 2.8 percent.