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Hydroelectric Energy

How it Works

Ever wonder what’s powering MUNI’s electric buses? The same force of gravity that propels your water across California, to your tap, is also harnessed to generate clean, 100% greenhouse gas-free Hetch Hetchy hydroelectric power. That’s right; your tap water powers MUNI’s electric buses. 150 miles before your Hetch Hetchy tap water gets to you, the very same water you use to quench your thirst has gone through turbines to generate clean energy for MUNI and a whole host of other City services. Hetch Hetchy powers all of the City’s municipal facilities (SFO, SFGH, MUNI, fire stations and more), residents and businesses in the San Francisco Shipyard, Treasure Island and other retail customers. In fact, your tap water powers about 17% of the City’s electricity needs. Pretty cool, right?

For more information on how hydroelectric energy works, please visit the U.S. Department of Energy's website by clicking here.

Key Facts
 • 385 MW of Greenhouse Gas-Free Hydroelectric Generation Capacity
•11 MW of Renewable Solar and Biogas Generation 
• 45,000 San Francisco Street Lights Powered with Clean Energy
• 160 Miles of Clean Energy Transmission Lines 
 
Moccasin Powerhouse   Side Profile Shot of HH
 Moccasin Power House  Hetch Hetchy Reservoir- O'Shaughnessy Dam


Hetch Hetchy Regional Hydroelectric Power System

The Hetch Hetchy Regional Power System is composed of three hydroelectric powerhouses: Moccasin Powerhouse, which includes a small, in-line hydroelectric unit, Kirkwood Powerhouse and Holm Powerhouse. The combined total hydroelectric generating capacity for these facilities is approximately 385 megawatts. Hydroelectric generation at Moccasin and Kirkwood Powerhouses rely on gravity-driven water flowing downhill from the Hetch Hetchy Reservoir. Holm Powerhouse generates energy from gravity-driven water flowing downhill from Cherry Lake. On average, the Hetch Hetchy Power System generates 1.6 billion kilowatt hours of clean, hydroelectric energy each year. The SFPUC provides this energy to its retail electric customers, wholesale electric customers and in normal-to-high precipitations years, the SFPUC sells this energy on the California energy markets

For a map of our power system, please visit our Hetchy Power System Map.

Moccasin Power House, featured above, is the powerhouse furthest downstream. The control room at Moccasin Powerhouse not only operates all three powerhouses, but also remotely starts and stops generating units, adjusts generator speeds and takes all necessary readings. Holm Powerhouse is the largest of the three powerhouses. San Francisco benefits immensely from owning and operating the Hetchy Power System. Hetch Hetchy hydroelectric energy is cost-effective and 100% greenhouse gas-free. It does not produce any harmful radioactive byproducts or leave behind any waste. Its cost-effective, clean electricity keeps our environment clean and helps the City’s fiscal bottom-line.


Last updated: 5/29/2018 11:26:47 AM