Now nearly 100 years old and by today's standards very small Piriaka was originally commissioned in 1924 being built to supply Taumarunui. In 1938 an agreement was signed with Government to connect the local system to the national electricity system. This was mainly due to the increase in population in Taumarunui. Another generator was added to the power station in 1971.
Power Capacity: 1.4 MW (2 x 0.23 MW, 1 x 1 MW) Owner: King Country Energy Ltd. "The Piriaka Scheme consists of a 3m high concrete weir and is approximately 485m long. The weir forms the head pond level. A 245m open canal diverts water from the Whanganui River to the head pond above the powerhouse. Water flows through a concrete penstock which is 2.8m dia x 200m long, to the powerhouse 8.2m below the head pond. This flow drives 3 generators before being discharged back to the river." (This arrangement with a small head of just 8 metres means that the scheme is essentially a run-of-river one.) "The Piriaka Station Powerhouse has 2 Vertical Francis turbines (0.3MW generators) and 1 Horizontal Kaplan turbine (1.2MW generator). The total rating is 1.8MW and the station mean output is 7GWh per year."