The 8-unit power station provides 1,070 megawatts (MW) of electricity by damming the Muddy Run ravine from its mouth. The station’s output is critical to meeting the dynamic peak electricity demands on the area’s regional power grid on hot summer afternoons. To generate electricity, the water in the upper reservoir at Muddy Run is used to fuel the turbines, flowing into the Conowingo Pond, a 14-mile stretch of the Susquehanna River in Maryland. As electricity demand decreases, at night, the units are reversed and used as pumps to fill the upper reservoir for subsequent peak-demand periods.

Muddy Run has provided electric power to the regional transmission system since commercial operation began in 1966. At the time, it was the largest pumped-storage hydroelectric power plant in the world. The general plant configuration remains the same as the original construction, however, the turbines and generators have been recently refurbished.

Open-loop Pumped Hydro Storage