The Huntly Coal Power Plant is the largest thermal power station in New Zealand and is located in the town of Huntly in the Waikato. It is operated by Genesis Energy, a state-owned enterprise, and supplies around 17% of the country's power.


The Huntly Coal Power Plant consists of three separate generating plants - a 1,000 MW coal-and-gas-fired steam plant, a 50 MW gas turbine generator, and a 385 MW combined cycle gas turbine plant.

Each of the four original generating units, which are capable of burning coal, gas, or both, installed in stages between 1973 and 1985, is capable of generating 250 MW (Megawatts) of electricity, giving a generating capacity of 1000 MW. Its chimneys are 150 metres high and each chimney has two flues that are 7 metres in diameter. The plant uses a reheat steam cycle, with C A Parsons turbines and Combustion Engineering boilers.

In 2004 the power station was upgraded with the addition of a 48MW gas turbine plant, and in 2007 the combined cycle gas turbine (CCGT) plant was commissioned. This plant increased the total generating capacity of Huntly by 385 MW (250 MW gas turbine + 135 MW steam turbine). The new turbine is a NZ$ 520 million investment and takes the total installed capacity to 1485MW.

Huntly runs at a load factor of 85% and is currently used to provide a large amount of the baseload energy needs of the northern North Island.

Fuel and coolant

Up to 50% of the coal used in the older section of the power plant is imported from Indonesia, and the remainder mined in New Zealand. The gas for the newer turbines comes from the Maui gas field in the Taranaki. Previous to the substitution of coal, Huntly used gas from the field to power the generation of the main units as well, but these were switched in the 1990s because of dwindling resources.

The Huntly Coal Power Plant uses water from the Waikato River for cooling. However, in order to protect aquatic life, conditions are imposed by its resource consent (see Resource Management Act), specifying the quantity of water that can be removed by the station along with the maximum temperature of the water when returned to the river (25°C). These conditions mean that on very hot summer days the station cannot operate at maximum capacity, and has sometimes effectively been shut down. A new cooling tower has been built as part of expansion works at the site, which allows one 250 MW unit to run at full load even during such times.

Transmission and distribution

Huntly Coal Power Stations's main electricity customer is Auckland, New Zealand's largest city, which lies 95 kilometres (59 mi) to the north of the station. It also has connections to supply electricity to Taranaki, the Ruapehu District and South Waikato, and is the connection point for the local distribution network in the Huntly area.

Two twin-circuit 220 kV lines originate from Huntly - one connecting to Otahuhu substation in Auckland via Glenbrook and Takanini (HLY-OTA-A), and the other connecting to Taumarunui via Te Kowhai (HLY-TMN-A), before carrying on to Stratford in Taranaki. An additional twin-circuit 220 kV deviation exists, connecting Huntly to the Otahuhu to Whakamaru C line at the newly-commissioned Ohinewai switching station.

Huntly Power Station
Country New Zealand
Locale Huntly, Waikato
Status Operational
Commission date 1983 (1983)
Owner(s) Genesis Energy

Power station information
Primary fuel Natural gas
Secondary fuel Coal (units 1-4)
Generation units 4× 250 MW steam turbine
1× 400 MW CCGT
1× 48 MW open-cycle
Combined cycle Unit 5 only

Power generation information
Installed capacity 1448 MW
Capacity factor 66.5%
Annual generation 8440 GWh