PG&E Corp's 404-megawatt Unit 1 at the Helms Pumped Storage hydropower station in California returned to service by early Friday, a spokesman for the company said. The company shut the unit for planned work by Thursday afternoon.
The 1,212 MW Helms station, which entered service in 1984, is located near Fresno in Fresno County. There are three 404 MW Units 1-3 at the station. With the return of Unit 1, all of the units were available for service.
One MW powers about 700 homes in California. Pumped storage plants store and produce electricity to supply peak power demands by moving water between reservoirs at different elevations. At times of low demand (and low power cost), the plant uses electricity from the grid to pump water into the higher reservoir. When demand and prices are higher, the station releases the water back into the lower reservoir through a turbine, generating energy.