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How Hydropower Works

Flowing water is a form of mechanical energy that can be used to produce electricity. This is called hydropower. PG&E uses two different types of hydropower facilities to generate electricity for customers in Northern and Central California. Here’s how hydropower facilities work:

  • Run-of-the-River Hydropower. A large pipe called a penstock carries water from a river downhill to a powerhouse, where the force of the water spins a turbine to create electricity. Then the water is returned to the river downstream.
  • Hydropower Dams. A dam is used to raise the water level of a river and create a reservoir. Water in the reservoir builds up pressure against the dam and can be released through a turbine to create electricity.

PG&E’s hydropower system—one of the largest in the country—includes more than 100 reservoirs. It is built along 16 river basins that flow across nearly 500 miles in our service area. This system employs close to 70 powerhouses, which can provide electricity for close to four million homes.

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