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Hydroelectric Power

Pennsylvania has 892 megawatts of conventional hydropower and 1,583 megawatts of pumped storage hydropower capacity and hundreds of people employed in the traditional hydro-electric field. The U.S. Department of Energy reports that hydroelectric power is the largest source of renewable electricity in the United States, producing about 6.3% of the nation's total electricity throughout the last decade.

Hydropower is a clean energy resource, can generate power quickly for emergency back-up, provide flood control, irrigation and water supply.

How Does Hydroelectric Power Work?

Hydroelectric power is the transformation of the kinetic energy of water, a function of mass and velocity of water flow. Hydroelectric power is created when the kinetic energy of flowing water is channeled by a dam into a turbine that spins a generator to convert the energy into electricity.

Energy 101: Hydropower

Types of Hydroelectric Power


These hydroelectric stations are those with small or no reservoir capacity so that only the water coming from upstream is available for generation at that moment and any oversupply must pass unused. A constant supply of water from a lake or existing reservoir upstream is a significant advantage in choosing sites for run-of-the-river. For more information visit the U.S. Energy Information Administration.

Low-Impact Hydro

These systems need to meet stringent environmental criteria such as river flow, water quality, fish passage and protection, threatened and endangered species, and public access/recreation.

Note: Both low impact hydro and run-of the river projects must adequately protect or mitigate their impact on the environment and society. For more information visit the Low Impact Hydropower Institute.

Conventional (dams) – Impoundment Hydropower

Most hydroelectric power comes from a dam that runs water into a turbine and generator. The power extracted from the water depends on the volume and on the difference in height between the source and the water's outflow. For more information visit the U.S. Energy Information Administration.

Pumped Storage

This method produces electricity to supply high peak demands by moving water between reservoirs at different elevations. At times of low electrical demand, the excess generation capacity is used to pump water into the higher reservoir. When the demand becomes greater, water is released back into the lower reservoir through a turbine.