What is Hydropower?

The hydroelectric facilities in the North Canal of the Lowell Hydroelectric Project, located within the Lowell National Historical Park, Massachusetts, overlook exposed bedrock in the river channel.

NPS

Hydropower, or hydroelectric power, is one of the oldest and largest sources of reliable, sustainable energy. It uses the natural flow of moving water to generate electricity. As of 2023, hydropower accounts for 27% of total U.S. renewable electricity and about 6% of total U.S. electricity generation.1

Hydropower technologies generate power by using the change in elevation from a dam or diversion structure to the powerhouse location, commonly referred to as “head." The amount of power generated is a combination of the project’s head and the amount of water available (flow). There are two primary types of hydropower facilities:

Conventional

• Conventional hydropower is the most common type of hydropower generation. These projects utilize a dam or diversion to direct water to a powerhouse located at the base of the dam or further downstream.

Pump Storage

• Pumped Storage works as a form of energy storage. Water is pumped from a lower to higher reservoir using lower cost electricity during periods of low energy demand. When the demand for electricity increases, the water is released back down to the lower reservoir, spinning a turbine, and generating electricity to meet the increased demand. Depending on the project, this cycle can be repeated daily or multiple times per day.

A license is required to operate most non-federal hydropower projects and non-federal projects attached to a federal dam. These licenses are issued by the Federal Energy Regulatory Commission (FERC) and have a duration of 30 to 50 years, at which point, the project is either relicensed or possibly surrendered. Hydropower licensing allows for a once-in-a-generation opportunity to provide reliable energy while balancing natural, cultural, and recreational resources. The Federal Power Act and other laws include provisions for agency, Tribal, and stakeholder engagement and a degree of shared decision-making.

To learn more about the FERC licensing process, visit FERC’s Hydropower Primer or visit our Hydropower Resources page.