This is a list of oldest hydroelectric power plants that are in operation.

Constructed in the 19th century Steigbachwerk, Immenstadt, Germany, 175 m. start 1880, 270 kW. years old. Ames Hydroelectric Generating Plant, Colorado, USA, constructed in 1890, years old. Nagold Hydroelectric Plant, Germany, since 1893, years oldWasserkraftwerk weckt die Neugierde der Nagolder (German) Mechanicville Hydroelectric Plant, USA, constructed in 1897, years old. Mambach Hydroelectric Plant, Germany, constructed in 1897, years old.[https://www.freiburg-schwarzwald.de/wasserkraft.htm#%C3%9Cber%2080%20Wasserkraftwerke%20im%20Kreis%20-%20gr%C3%B6%C3%9Ftes%20Kleinkraftwerk%20in%20Mambach Wasserkraft im Breisgau und Hochschwarzwald]

Constructed in the 20th century Appleton Powerhouse, USA, 2.2MW, constructed in 1901, years old. Landara Hydroelectric Plant, Bolivia, opened 1902, years old.Potencial y aprovechamiento de la hidroenergía en Bolivia Quintana Hydroelectric Plant, Spain, operational since 1902, years old. 18.45 metres, rated output of 7.8 MW, producing an annual average of 23 GWh Necaxa Hydroelectric Plant, Mexico, opened in 1905, years old. Both the plant and parts of the original transmission line are still in service.Water power at Necaxa Falls in Mexico. Electrical World and Engineer, vol. 46, no. 18, p. 729-735. New York, October 28, 1905 Lockport Powerhouse, Illinois, USA, 1907. Now generating 13.4 MW on the Chicago Ship and Sanitary Canal. Keokuk Energy Center (Lock and Dam No. 19), Iowa, USA, 142MW, constructed in 1910. years old. La Calera Hydroelectric Plant, Cordoba, Argentina, constructed in 1911.Central La Calera years old. Pharping Hydropower Station, Nepal, 500kW, constructed in 1911, years old. Coyas Hydroelectric Plant, Chile, since 1911,Hidroeléctricas Coya y Pangal years old Pilchowice Hydroelectric Plant, Poland, operational 1912, years old. Shilongba Hydropower Station, China, operational 1912, years old. Laufenburg Hydroelectric Plant, Germany/Switzerland, operational 1914, years old. Big Quinnesec Falls, USA, 4.4 MW, constructed in 1914, years old. Brule Power Station, Wisconsin, USA, 5.3 MW, constructed in 1919, years old. Fala Hydro Power Plant, Slovenia, constructed in 1918, years old.

Defunct stations Rheinfelden Hydroelectric Plant, Germany/Switzerland, opened 1898, closed and demolished in 2010, serving 112 years.Udo Leuschner: Energie-Chronik. Accessdate 2025-09-12.

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