In this part of the country, peaks are usually on hot summer afternoons and cold winter mornings during the work week. Water is generally pumped back to the upper reservoir at night and on weekends. Duke's baseload generating stations operate around the clock and supply the energy needed to refill the lake. The baseload stations include efficient nuclear and coal-fired power plants. Pumped-storage and conventional hydroelectric plants are ideal for meeting demand during peak periods.
Water power uses no fuel in the generation of electricity and so has very low operating costs.
By using the same water over and over again, a pumped storage plant extends and makes more efficient use of water resources.