U.S. electricity rates should drop around one cent per kilowatt-hour by the year 2020, carbon gas emissions continue to rise and more than40 percent of the nation's nuclear power capacity go out of service, according to the government's annual long-term energy outlook yesterday. To keep pace with growth, Department of Energy (DOE) projections said the equivalent of 1,000 new power plants of an average size of 300 megawatts are needed in the next 20 years.