The Folsom Powerhouse, using part of the American River's rushing water to power its turbines connected to newly invented AC generators, generated three phase 60 cycle AC electricity (the same that's used today in the United States) that was boosted by newly invented transformers from 800 volts as generated to 11,000 volts and transmitted to Sacramento over a 22 mi (35 km)-long distribution line, one of the longest electrical distribution lines in the United States at the time.

The Folsom Powerhouse was one of the first examples of significant electrical power being generated and economically shipped to where it could be used.

Historic photos, interpretive exhibits and docent guided tours by the California State Park Service explain how the powerhouse worked.

It began with one direct current generator powered by a coal burning steam engine, and it started generating electricity on September 4, 1882, serving an initial load of 400 incandescent lamps used by 85 customers located within about 2 miles (3.2 km) of the station.

Only two of the four alternating current generators were operating on July 13, 1895, when the powerhouse provided the first electricity to Sacramento via 22 miles (35 km) of transmission lines, making it one of the first places in the United States to transmit long-distance hydroelectric power.

[8] The International Electro-Technical Exhibition - 1891 in Frankfurt am Main Germany demonstrated an earlier instance of long distance AC transmission of hydroelectric power.

The dam diverted a large stream of water into a 2.5 miles (4.0 km) long diversion canal—the East Canal.

The AC generators, some of the largest designed and built up to that time, were powered via four penstocks full of rushing water driving four large turbines.

The four large water turbines, some of the largest built up to that time, were made by S. Morgan Smith Works of York, Pennsylvania.

The 750-kilowatt (1,005 horsepower) alternating current generators were made in the newly incorporated General Electric plant in Schenectady, New York.

Each of the six branch circuits make their way three times progressively around the rotor in right hand flattened spirals.

To allow customers to use electric clocks regulated by synchronous motors, a Frequency "Indicator" was added to the Powerhouse switchboard.

To allow parallel alternators and power grid, a Synchroscope was added to the Switch Panel.

The AC power generated (about 4,020 horse power or 3 MW) at the Folsom hydroelectric facility was converted to 11,000 volts at the power plant by twelve new (in 1895) air cooled transformers invented by William Stanley, Jr. and transmitted to Sacramento on twelve bare #1 AVG copper wires held by ceramic insulators that were attached to the cross beams mounted on two sets of 40 feet (12 m) cedar poles.

The first heavy AC motor users were various factories which typically replaced their steam power plants.

[10] A second powerhouse was constructed below the original facility in 1897 to house an additional 750-kilowatt AC generator to meet the growing residential and public transit electricity demands of Sacramento.

Larger hydroelectric plants and dams were built along the Yuba, Feather, and Tuolumne Rivers in order to provide power for Northern California.

The San Francisco-based California Gas and Electric Company bought the Folsom Powerhouse by 1902.