Last updated: 07 Mar 2025
What are we doing?
Transpower is investigating possible electricity infrastructure investments for the upper South Island, north of Twizel, to ensure a reliable power supply for the future as the region grows and more homes and businesses switch their energy use to electricity.
Why are we doing it?
Electricity use across the upper South Island has been rising steadily, particularly during summer, when power is used for irrigation. With the growing shift toward a lower carbon, more electrified way of life and forecast electrification of South Canterbury primary processing, demand for electricity is expected to increase further.
In the upper South Island, there is not enough electricity generation to meet demand. Electricity is supplied into the upper South Island through high-voltage transmission lines coming north from the Waitaki Valley.
Long distance transmission like this requires additional voltage support to help maintain a reliable supply of electricity. Voltage support tools and equipment include bus couplers, switching stations and dynamic reactive support.
In 2012 we began investigating long-term development plans to ensure voltage stability is maintained in the upper South Island. As the immediate need was relatively urgent, but the longer-term outlook was uncertain, we decided to split the investment into stages:
- Stage 1, a low-cost investment for a new bus coupler at Islington Substation – a short-term deferral
- Stage 2, a second (and potentially much larger) investment.
How will this affect you?
We want to hear what you have to say on our plans for electricity infrastructure in the Upper South Island.
This could include your thoughts on the preferred options, our assessment of the benefits, the electricity demand and generation scenarios we have used, or our short-listing criteria. We value your feedback, and it will be considered ahead of Transpower's final decision on how to proceed with the future of electricity infrastructure in the Upper South Island.
Timeline and updates
Stage 1
The Stage 1 project sought funds to install a sixth 220 kV bus coupler at Islington Substation. This was a low-cost measure which allowed end-of-life voltage stability equipment at Islington to be decommissioned and at the same time ensured no voltage instability issues in the short term. The project also sought funds to investigate future switching station options further. We submitted our Stage 1 proposal in June 2012, and it was approved by the Commerce Commission in February 2013. The project was delivered and the bus coupler commissioned in 2014.
Following the switching station investigation that was part of Stage 1, in 2015 we sought and received an approved Output Amendment to our Stage 1 proposal from the Commerce Commission to add the ability to secure designations and property rights for potential switching stations in the future at two locations, Orari and Rangitata. This was to ensure that switching stations could be commissioned in time, if switching stations proved to be the preferred option to meet the voltage management needs for Stage 2. We actioned this as part of Stage 1. This Output Amendment has allowed this option to remain possible, but does not preclude the Stage 2 investigation process, which will involve long-listing and short-listing processes and consultations, and which may result in a different preferred solution.
Stage 2
We are now in Stage 2 of this project. The short-list consultation is open from 18 December 2024 – 14 February 2025. See the short-list consultation documents and how to submit feedback.
We held a long-list consultation in August-October 2023. This was the first consultation to seek feedback about our thinking, assumptions, and possible early options for upgrades on the high-voltage electricity transmission network for the Upper South Island region.
Hearing from those interested in potential new generation, planned commercial or residential developments, and industrial conversions from fossil fuels to electricity helps us better understand what is happening, and what the future need for electricity will be.
The information received will help us refine our thinking and planning about the options we are looking into to provide for future growth.
This will provide further details about the project and an opportunity for industry and stakeholders to input into our thinking. This contribution is essential to help us refine our thinking and progress to a short-list consultation.
What happens next?
In 2025, Transpower will review all the feedback received, refine the analysis as needed, and then decide whether to submit a proposal to the Commerce Commission for transmission infrastructure for the upper South Island.
Keep an eye out for updates on this webpage or email us at [email protected] to receive an email at project milestones.
More information
Click here to read our summary document to inform any submission you might like to make on our shortlist consultation.
Click here to view the long-list consultation documents.
Transpower's Notice of Intention to the Commerce Commission
This letter outlines our planned Major Capex Proposal project for the upper South Island upgrade project to the Commerce Commission, identifying the envisaged approach to staging investments and suggesting a timeline.
Letter from the Commerce Commission agreeing preliminary matters and timeframes
The Commerce Commission responds formally to our Notice of Intention, expressing comfort with proposed approach and agreeing a timeline for the process, as is required under cl 3.3.1(3) of the Capex IM.