Stored and renewable energy accounted for 4% of the electricity generating capacity in the United States in 2016, according to the U.S. Energy Information Administration.
Hydroelectric pumped storage plants accounted for 23 gigawatts of capacity. The plants, of which 88% were built before 1990, “produce electricity from water previously pumped to an upper reservoir,” according to the EIA. The plants can be scaled down or up depending on demand. The largest U.S. plant is Bath County in Virginia, with more than 3 gigawatts of pumped storage capacity.
Utility-scale geothermal plants comprised of 3.7 gigawatts of electricity generating capacity. The largest U.S. plant, the Geysers in northern California, accounts for 943 megawatts of geothermal capacity. “All geothermal capacity is located in seven states in the western United States,” according to the EIA.
Wood and wood waste biomass had 10.2 gigawatts of capacity, making up the largest share of biomass technologies. Municipal solid waste, landfill gas and other waste biomass had capacities of 2.2 gigawatts, 2.1 gigawatts and 0.8 gigawatts, respectively. Landfill gas and wood and wood waste plants are in 44 states and 32 states, respectively.
“Batteries and flywheels, which provide electricity storage, are amoung the newest operating units, as almost all of these generators have been added since 2010,” according to the EIA. “Half of the United States’ 540 megawatts of batteries are in California, Illinois and West Virginia.” Nearly all of the utility-scale flywheels, with 44 megawatts of capacity, are in New York and Pennsylvania.