Mercury to invest NZD 1 billion to expand capacity of operating geothermal fields in New Zealand
The Rotokawa geothermal power station in New Zealand (source: Mercury)
Carlo Cariaga
14 May 2026
Mercury will be investing NZD 1 billion to expand the power generation capacity of the Rotokawa and Nga Tamariki geothermal fields in New Zealand.
Mercury has announced an investment plan for NZD 1 billion (approx. USD 592 million) for the drilling of new wells and potential expansion of power generation capacity at the Nga Tamariki and Rotokawa geothermal fields in New Zealand. The expansion plan could increase output by 1 TWh, with the first power generation targeted by 2030.
The expansion plans were announced as part of Mercury’s Geothermal Investor Day. The presentation material can be accessed via this link.
A NZD 75 million capital for the drilling of 3 appraisal wells has already been committed for FY 2027-2028. The target new capacity/output to be developed includes 50 MW / 420 GWh in Rotokawa and another 75 MW / 620 GWh in Nga Tamariki. The announcement of the growth strategy comes just a few months after the opening of the 55-MW Nga Tamariki Unit 5.
The company states that it is funding the growth from its own balance sheet and within clear financial guardrails. The company sees this as a value accretive investment with will support resilient earnings and balance sheet strength.
Beyond the immediate expansion plans, Mercury sees opportunity for up to 5 GWh of new geothermal power generation output. This includes potential growth in Kawerau, Mokai, and Rotoma, which is a greenfield site with potential of 50 to 100 MW.
Next-generation geothermal part of long-term strategy
Mercury also envisions a long-term geothermal growth horizon that includes new greenfield options, as well as opportunities to develop superhot geothermal and enhanced geothermal projects. It must be noted that the first superhot geothermal well in New Zealand will be drilled in the Rotokawa field, known to be the hottest geothermal reservoir in the country.
“Scaling our geothermal platform will strengthen our renewable portfolio, support long-term contracting with major energy users, and help meet New Zealand’s growing demand for affordable, reliable and renewable electricity,” said Mercury CEO Stew Hamilton. “We have a credible, investable and repeatable geothermal platform, a strong pipeline of opportunities, and the capability and partnerships to deliver.”
Geothermal growth horizon
Source: Mercury
