New Zealand has a long history in geothermal electricity generation and today geothermal energy produces almost 20% of New Zealand’s electricity supply. Most of New Zealand’s installed geothermal generating capacity,, is situated in the Taupo Volcanic Zone, with about 25 MWe installed at Ngawha (link to section on Ngawha) in Northland.
Power companies in New Zealand generate roughly 7,500 GWh per year from 19 power plants located over 8 high-temperature fields. The temperature and conditions of a particular geothermal reservoir determine generation technology (hyperlink). Generation units span the spectrum of power technologies from a simple binary, to 2-phase binary, to condensing steam turbines (single, double and triple flash) and back-pressure turbines. Individual unit sizes range from 3.3 MWe (binary Kawerau) to 133 MWe (NAP, Rotowaka). Among the original equipment manufacturers, Ormat is the market leader with 300 MWe commissioned, followed by Fuji (285), Toshiba (160), British Thompson and Houston (128), Mitsubishi (42), and other (8).
Five entities operate geothermal power stations: Mercury Energy (489 MWe), Contact Energy (420), Top Energy (25 MW), Ngati Tuwharotoa Geothermal Ventures (20.5), Eastland Energy (9.5), and Nova (3.3). Three fields (Mokai, Ngatamariki, and Rotokawa) have operations that are co-owned with local iwi.