Mercury NZ (ASX:MCY) has commissioned its NZ$220 million expansion of the Ngā Tamariki Geothermal Station near Taupō.
The project, which was completed in just under two years, introduces a high-tech fifth generation unit that adds 55MW of capacity to the national grid.
The single unit produces more than double the output of the station's original 2013 components, boosting total annual generation to approximately 1120GWh—enough renewable energy to power every residential home in Christchurch.
The expansion was inaugurated by Mercury CEO Stew Hamilton alongside Associate Minister of Energy Shane Jones and local iwi partners.
Beyond sheer power output, the project marks a technical breakthrough in sustainability; it includes a new system designed to reinject non-condensable gases, primarily carbon dioxide, back into the geothermal reservoir.
The innovation is expected to help Mercury achieve a 70% reduction in the station's carbon emissions by 2030.
Hamilton emphasised that geothermal energy is a critical pillar for New Zealand's energy security, providing "steady baseload supply" that operates 24/7.
Unlike intermittent wind or solar, this reliable output stabilises the grid during winter peaks and supports long-term affordability.
The project is a key component of Mercury's broader strategy to deliver 3.5 TWh of new renewable generation by the end of the decade, eventually meeting roughly 8% of the country’s total annual energy demand.
At the time of reporting, Mercury NZ's share price was $5.30.