WHAKAMARU BATTERY ENERGY STORAGE SYSTEM.
We're in the early stages of planning a Battery Energy Storage System (BESS) near Whakamaru Hydro Power Station on the Waikato River, north of Taupō.
This site is ideal because it's flat and next to Transpower’s Whakamaru sub-station and transmission lines, connecting to the national power grid.
A new battery storage system will complement our existing renewable energy generation capabilities.
We'll charge up the batteries with power primarily from the National Grid when there’s plenty of power around, and then use it when there's high demand. At times it will be charged from our Whakamaru hydro power station next door. These batteries will help manage the peaks of demand through adjusting the ability to supply electricity when it’s needed across Aotearoa New Zealand.
What could the BESS look like?
We’re still in the early design stage but we think our BESS could consist of up to 180 battery containers on concrete foundations, a substation, cabling, switch rooms and an operations and maintenance building.
Each container is about 6m long and 2.6m high, about the size of an average caravan.
Project site
Whakamaru is the heart of our Waikato Hydro System which supplies around 10% of New Zealand’s renewable electricity. It's also a major node for North Island power transmission.
The hydro station and dam were constructed on the Waikato River in 1956. Its four generation units were refurbished in 2020 which increased generation capacity to 124MW.
Transpower operates two substations, a switchyard and line connections, along with multiple 220kv overhead lines and one 400kv overhead line near the power station.
We're working with the Taupō District Council, iwi partners and stakeholders to keep the community informed on progress with this project.
In May 2025, Taupō District Council granted resource consent for the project. This means we can start to think about when we want to build the first stage of the battery storage system. The next major milestone will be when we consider whether to proceed with the project and we’re aiming for that decision to be mid-2026.
Please watch this page for updates. People can also contact the project team via email on: whakamaru@mercury.co.nz
We have been granted resource consent for the BESS. We will make a decision on whether to build the project by mid-2026. Progressing the project may take longer as we want to get everything right first.
We’re building on the experience of our pioneering direct grid-connected 1MW/ 2MWh battery that we piloted at our Southdown Power Station in 2018, a Kiwi first. At that time, we invested more than $2 million to understand how battery technologies can play a part in the future of New Zealand’s electricity ecosystem.
It will have a total installed capacity of between 200-300MW. The BESS will connect to an existing 220 kV line via a new 33kV underground cabling into a new switching substation, and then into the Transpower substation, and onto the national grid.
There is growth in renewable energy generation as New Zealand moves to a low carbon economy. But renewable energy like solar and wind are intermittent which means Battery Energy Storage Systems, which can be flicked on to supply power quickly, are important to manage winter peaks, and to make the national power grid resilient. Think of battery power as a quick start generator that can be used when solar, wind or hydro generation are not meeting demand.
We shared information via a letterbox drop, a drop-in event, and via the Mangakino-Pouākani Representative Group meeting. We've been talking with Ngāti Raukawa and with other iwi in the area. We’ll continue to engage with people as the project progresses.
The site is separate from the river and should have no impact.
We will be careful about the impact noise will have. The project is still being designed, and part of that is looking at different layouts on the site and modelling noise levels.
Vehicle numbers will increase during construction but not so much that they will cause disruption to traffic flow. There will be an increase in large vehicles, like trucks and trailer units, for battery deliveries. We'll work with local businesses and schools to ensure traffic management planning is in place to reduce any disruption.
Vehicle numbers will increase during construction but not so much that they would cause disruption to traffic flow. There will be an increase in large vehicles, like truck and trailer units, for battery deliveries. We'll work with local businesses and schools to ensure traffic management planning is in place to reduce any disruption.
As we start to develop plans, we'll continue to engage with stakeholders and local community to let them know what's planned. If you would like to contact the project team, please email: whakamaru@mercury.co.nz