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Mangorei Power Station

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Mangorei Hydroelectric Power Station first supplied power to New Plymouth in 1906. The present 25 metre (m) high earth dam across the Mangamahoe Stream was completed in 1931 and enables the Station’s average annual output of 20.9 GWh. Recent efficiency projects include upgrading the Scheme’s water supply tunnels and turbines; while environmental measures include a fish pass and a trap and transfer programme for eels.

At a Glance


Commissioned 1931

Max Capacity 4.5 MW

Annual output 20.9 GWh

The original Mangorei Station was constructed in 1904 and used water from the Waiwakaiho River, supplying power for New Plymouth street lighting and 41 customers. Increased demand led to the Mangamahoe Stream dam. On completion in 1931, this was the highest earth dam in Australasia. It supplies water via two tunnels to three 1.3 MW and one 700 kW generator. 

In recent years, we have put real focus on improving the scheme’s efficiency. There’s been extensive work on the supply tunnel linings to reduce friction. An upgrade of the turbines is due in the near future too. 

Environment and recreation 

As part of our environmental commitment, we have installed a fish pass. There’s also a successful trap and transfer programme to avoid any disruption to the migration of Longfin Eels. We maintain a minimum downstream river flow, regardless of our generation requirements. 

We gained new Resource Consents for the scheme in 1996. Consents will again be due for renewal in 2021.

Mangorei Penstock Manifold
Mangorei Penstock Manifold

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