The Mangahao station was officially opened in November 1924 by then Prime Minister Bill Massey.  Over 80 years on, the station continues to provide a valuable contribution to the national grid both in terms of generation output and voltage support to the Cook Strait DC inter-island cable. 

Todd Energy is responsible for operating the Mangahao station which it acquired in 1997 in a 50:50 Joint Venture with King Country Energy.

The headwaters of the Mangahao River are a major tributary of the Manawatu River.  The total catchment area of the scheme is 86 square kilometres in an area of high annual rainfall, which on average exceeds 3,700 millimetres.

Water stored in the reservoirs formed by the two dams on the Mangahao River is brought by a 1.6km long tunnel to the third reservoir on the Tokomaru stream and then to the surge chamber via a 2.1km tunnel.

The output from Mangahao was increased in 2004 with the addition of a mini-hydro station that produces an additional 10GWh of electricity per year – enough to power around 1,250 households or a town the size of Turangi.  This output is on top of the 126GWh/year that is produced by the existing power station at Mangahao.