How a Little-Known Powerhouse Keeps San Francisco Running

Moccasin Powerhouse is situated near the base of beautiful rolling hills along a creek in Tuolumne County 130 miles east of San Francisco. Unbeknownst to many a visitor passing by, it is a vital resource in the City & County of San Francisco’s Regional Water and Power System. One of three hydroelectric power plants operated by the SFPUC, it produces clean electricity that helps power critical municipal services in the city – like Muni trains and streetlights.

Moccasin Powerhouse, which opened in 1925 and was replaced with a new facility in 1969, relies on gravity to transport water from Hetch Hetchy Reservoir, approximately 20 miles away in Yosemite National Park. As the water makes its way from the Sierra’s and nears Moccasin, it plunges 1,300 feet down, flowing through four penstocks before arriving at the Moccasin Powerhouse where its rushing force helps spin two Pelton turbine units that generate 100 percent greenhouse gas-free hydro-electricity.

The Moccasin Powerhouse is a powerful place—literally. It can generate a maximum of 405 megawatts per hour. On average, up to four Power System Operators—including one supervisor—are on 12-hour shifts every day of the year overseeing the facility in the Powerhouse Operating Center. They are supported by transmission line engineers, two crews of transmission line workers, and utility mechanics. These are electricians and technicians working to repair and maintain the powerhouse equipment.

Employees who work at Moccasin and the nearby area praise its awe-inspiring beauty. Scott Riley, maintenance planning manager, began his career in San Francisco but noted the City’s waterfront parks and cityscapes “don’t compare to the natural colors and wonders of the Hetch Hetchy Water and Power System, from the beauty of fresh fallen winter snow, the spring colors of a mountain meadow, the raging swollen rivers in the summer sun…”

Employees also note the friendly culture as well. Employees travel around a lot—by foot and vehicle—to buildings, jobsites, and into and out of the Moccasin area. When one says “Hello, how are you?” the Hetchy answer is often “Living the dream.” It says it all, doesn’t it?

For over 100 years, Hetch Hetchy Power has traveled from the Moccasin Powerhouse to San Francisco. Thanks to the powerhouse, we can keep Muni trains moving, our streets well light at night, and critical emergency services like Zuckerberg General Hospital fully powered. Today, Hetch Hetchy Power generated at Moccasin serves nearly 20 percent of the electrical demand in San Francisco.

Want to visit the Moccasin Powerhouse without leaving the couch? Check out our mini virtual tour of the area: