Originally constructed in 1904 and using water from the Waiwakaiho River, the Mangorei Power Station first supplied power in 1906 – for street lighting and 41 customers in New Plymouth.

A steady increase in demand for electricity resulted in plans to store water for generation purposes behind a dam across the Mangamahoe Stream, with work finally starting in 1930. Said at the time of its completion in 1931 to be the highest earth dam in Australasia, the 25-metre high dam supplies water via two tunnels to three 1.3 MW and one 700 kW horizontal generating sets.

With a total capacity of 4.5 MW, the Mangorei Power Scheme has an average annual output of 20.9 GWh.

To address the potential environmental effects associated with the scheme, TrustPower has installed a fish pass and initiated a regime to maintain a residual downstream river flow regardless of generation requirements.

A successful trap and transfer programme for adult eels has also been implemented to ensure migration of this species is not adversely affected.

Resource Consent applications to re-permit the existing scheme were approved in 1996 for a 25 year term.

As with the Motukawa scheme, Mangorei has been subject to intensive studies to improve conveyance and energy conversion efficiency. Extensive work on the supply tunnel lining, to reduce friction, has now been completed and an upgrade of the turbines is underway.