NGĀ TAMARIKI
GEOTHERMAL STATION

Ngā Tamariki Geothermal Station

Opened: 2013
Expanded: 2026
Generating Units: Five
Installed Capacity: 132MW
Average Annual Output: approximately 1,120GWh

Ngā Tamariki Geothermal Station is located 17km northeast of Taupō and generates renewable electricity 24 hours a day.

Originally commissioned with four generation units in 2013, the station was expanded in 2026 with the addition of a fifth unit. The expansion increased the station’s installed capacity from 86MW to 132MW and lifted its average annual generation from approximately 730GWh to 1,120GWh.

Ngā Tamariki provides steady renewable generation that is available around the clock.

Geothermal generation complements weather-dependent renewable sources such as hydro and wind, supporting electricity supply during periods of high demand and when weather conditions affect other forms of renewable generation.

The station’s average annual output of approximately 1,120GWh is the equivalent to enough electricity to power approximately 160,000 average NZ homes.

(Based on an average household usage of 7,000kWh per annum).

Developed through enduring partnerships

The geothermal resource at Ngā Tamariki has been developed in partnership with Tauhara North No.2 Trust, which jointly owns the resource consents, receives a revenue stream from the station and has options to take an equity interest.

Mercury works with Tauhara North No.2 Trust and mana whenua Ngāti Tahu Ngāti Whaoa to support the sustainable management of the geothermal resource and surrounding environment.

The station is located on Wairakei Pastoral Estate, where electricity generation operates alongside farming activities.

How the station works

Ngā Tamariki uses hot geothermal fluid drawn from deep underground to generate electricity.

The geothermal fluid transfers its heat to a separate working fluid, which drives turbines connected to generators. The geothermal fluid is then reinjected into the reservoir to support its long-term sustainability.

The station has geothermal wells extending to depths of more than 3,000 metres and reaching temperatures of up to 290°C.

Reducing emissions through reinjection

Ngā Tamariki reinjects non-condensable gases, primarily carbon dioxide, back into the geothermal reservoir rather than releasing them into the atmosphere.

Mercury was the first electricity generator in New Zealand to undertake this type of reinjection at a geothermal power station.

Following completion of the fifth generation unit, reinjection can be undertaken across all five units. This is expected to help reduce the station’s carbon emissions by 70% by 2030.

Station history

Exploration of the Ngā Tamariki geothermal field began in the 1980s.

Mercury commissioned the original four-unit station in 2013. The station was designed using binary-cycle technology, which allows electricity to be generated from lower-temperature geothermal resources.

In 2024, Mercury began construction of a fifth generation unit to increase the station’s renewable output.

Expansion completed in 2026

Mercury completed the $220 million expansion of Ngā Tamariki in 2026, adding a fifth generation unit to the station.

Construction began in May 2024 and was completed in just under two years.

The project increased the station’s installed capacity from 86MW to 132MW and added approximately 390GWh of average annual generation.

Two geothermal wells were drilled as part of the project: one to supply geothermal fluid to the new unit and another to reinject geothermal fluid and support the long-term sustainability of the reservoir.

Around 300 Mercury people, contractors and consultants contributed to the project, with more than 250,000 hours worked during construction without a serious-harm incident.

Expansion Project timeline

The expansion of Ngā Tamariki was one of Mercury’s major renewable generation projects. The following images, videos and updates capture key stages in the construction and commissioning of the fifth generation unit.

May 2024 - Construction begins

Aerial photo of Ngā Tamariki Geothermal Station before 5th generation unit built - May 2024

Physical construction of the fifth generation unit began in May 2024.

September 2025 - Construction reaches approximately 80%

Aerial photo of Ngā Tamariki Geothermal station - 5th generation unit 80% built Sept 2025

The fifth generation unit under construction in September 2025, when the project was approximately 80% complete.

October 2025 - Construction update video

Watch: Ngā Tamariki expansion construction update — October 2025
Note: This video was produced while construction of the fifth generation unit was under way.

January 2026 - First electricity delivered

The fifth generation unit began delivering electricity to the national grid as testing and commissioning progressed.

March 2026 - Expansion completed and opened

The completed fifth generation unit was officially opened with mana whenua, commercial partners, landowners, community representatives and members of the project team.