MERCURY NEWS

25 September 2025

Final milestone in Karāpiro Upgrade Project reached

The third and final generator unit at Karāpiro Hydro Station has been installed.

Mercury have completed testing and commissioning the third and final new generator unit at the 78-year-old Karāpiro Hyrdo Station, bringing the $90 million, multi-year refurbishment project to a close.

This project started in 2018 and work on site began about three years ago.

The project fully replaced all three of the generators at the station, their turbines and water intake gates. The upgrade means that the capacity at Karāpiro Hydro Station has increased by an additional 16.5MW, taking it from 96MW to 112.5MW improving the average annual energy production by 32GWh. The station’s total average annual output is now 537GWh, producing enough electricity to power the equivalent of 63,000 average homes a year.

The upgrade also ensures the hydro station will continue to generate power for another 50 years.

Some statistical highlights from the project are:

• 150 weeks of outage time.
• About 260,000 hours worked and about 450,000 hours in total including offsite fabrication.
• 1500 tonnes of scrap metal removed, and new equipment imported, (equivalent of 125 double decker buses).
• 25km of cable installed.
• First time a runner chamber has been replaced in New Zealand.

Head gate lift for the first unit at Karāpiro Hydro Power Station, April 2023

Technical details:

• Full replacement of the three generators, turbines and water intake gates.
• Added 16.5MW of generation capacity to the station.
• Improved turbine efficiency; the new units generate about 4% more power from the same water flow.
• Designed for a further 50-plus years of reliable renewable generation.
• Ensures compliance to modern dam safety standards.

This milestone marks a significant investment in New Zealand’s renewable energy future, reinforcing Mercury’s commitment to sustainability and innovation.

The project at the Karāpiro Hydro Station is part of a long-term refurbishment programme to upgrade each of the nine hydro stations on the Waikato River.

Mercury will now turn its focus towards planning to upgrade the Maraetai I, Ōhakuri and Atiamuri hydro stations. representing a further $550m investment into renewable energy.