Hydro power facilities are oldest power plants in the U.S.

The oldest power generating facilities in the U.S. are hyrdoelectric plants, which are on average 64 years old. But some are even older–dating to before 1908, according to analysis by the U.S. Department of Energy.

Hydroelectricity remains the primary source of renewable energy in the U.S., and it now generates around six or seven percent of the country’s power. In 2015, renewable energy contributed around 14 percent of the country’s power, driven by hydro, wind and solar.

Most states have hydroelectric plants, but half of the country’s hydro power capacity is in three states, Washington, California and Oregon.  Texas has few hydro plants that together generate only about 500 to 1,000 megawatts. (One megawatt is enough to power 200 average homes on a hot Texas day.)

The pitfalls of the country’s aging hydroelectric plants have been highlighted recently by California’s Oroville Dam, which state officials worried would fail following heavy rain. Damage to the dam could affect it’s hydroelectric facility, which dates from 1968 — old by modern standards for electricity generators, but newer than most of California’s hydro power facilities.

Hydro plants have the capacity to generate 13 percent of California’s power, and the Oroville Dam facility accounts for 7 percent of that.