Construction of the Waihopai Power Station began in June 1925, with its power output first supplying Blenheim and the surrounding area in August 1927.

Originally of 1 MW capacity and intended to supply the entire Marlborough province, the Waihopai scheme was expanded to meet growing demands for electricity through the installation of diesel generating sets in 1930 and 1937. Plans to further increase capacity during 1943 were blocked due to Government wartime import restrictions. In 1996, a new 2 MW generator and turbine were installed to replace one of the existing 500 kW units. This and other upgrade work has seen the scheme’s maximum output increase to 2.4 MW, with an annual generation output of 11.8 GWh.

The scheme was granted Resource Consents for a further 35 years during 2004.

Since that time a successful elver and koura trap and transfer programme has been implemented to enhance the overall eel population within the catchment.