In February 2025 we concluded consultation on an initial short-list of investment options to ensure a reliable power supply for the upper South Island (from Twizel north).
Since then, we have undertaken further revision of our cost estimates, incorporating a more detailed understanding of the activities, resources and scope of work required. All cost estimates for short-listed options have increased, driven by requirements for transmission line upgrades which have proven more complex than we anticipated.
Our preferred option has increased to approximately $164 million, compared to the $77 million presented in our short-list consultation.
We have also continued to review our assumptions used in our benefit modelling, and a more accurate representation of constraints has led to greater benefits than initially estimated. Under the Transmission Pricing Methodology, this led to a change in the allocation of costs.
The need and requirement for investment has not changed and remains essential to ensure voltage stability can be maintained in the upper South Island as electricity use increases further.
Further public consultation took place from April - May 2025 on the short-list of preferred options. Our consultation information included an overview document and five attached documents, each of which focused on a specific aspect of our consultation.
Documents for further consultation:
- Upper South Island - further consultation document
- USI Attachment 1 - Need for Investment, Demand and Generation Scenarios
- USI Attachment 2 - Short-list of investment options
- USI Attachment 3 - Benefit modeling
- USI Attachment 4 - Options analysis
- USI Attachment 5 - Indicative starting BBI customer allocations
Consultation responses
Thank you to those who made submissions.
Please see the USI summary of submissions for a summary of the key points raised and Transpower's responses. Individual submissions on the short-list options are published below:
What is the timeframe from here?
We have submitted our proposal to the Commerce Commission. The Commission will now now consider and consult on our proposal, as part of its process to ensure New Zealanders receive good value for money from our investments.
Previous documents
- Upper South Island upgrade project page
- Our long-list consultation page
- Our short-list consultation page
Please contact us at [email protected] if you have any questions.