HVDC Submarine Cable Replacement and Enhancement Investigation

Last updated: 13 Dec 2024

Oteranga Bay viewed from the water

What we're doing 

Transpower plans to replace the ageing electricity cables that cross the Cook Strait at the end of the decade and is considering whether to also increase the capacity of the cables at the same time. 

In December 2024 Transpower secured global cable solutions supplier Prysmian to replace the submarine electricity cables by early 2032. The agreement reserves the cable manufacturing, the ship, and the experts to install the cable and ensures the project will go ahead. 

Latest News: 

Why we're doing it 

The submarine electricity cables connecting New Zealand’s North and South Islands are nearing the end of their operational life and, due to international supply constraints for submarine cables, Transpower has in 2024 secured a cable supplier to replace the cables.. Transpower’s provisional analysis shows that increasing the capacity of the cables from the existing 1200 MW to 1400 MW would provide good value for New Zealand and future-proof this part of the electricity system. 

Our High Voltage Direct Current (HVDC) inter-island link is a key part of New Zealand's National Grid - transporting bulk electricity between the North and South Islands and balancing New Zealand's energy demands. 

When this will happen 

This work is planned to happen between now and the early 2030s. 

Indicative dates 

  • August 2024 - Published an information and consultation paper. 
  • October/November 2024 - Transpower completed a high-level evaluation of costs and benefits and decided to enter contract negotiations with the option of installing replacement cables with a 1400 MW capacity. 
  • December 2024 - Transpower entered a formal Capacity and Reservation agreement with a supplier. A deposit to the supplier is required to secure the manufacturing and installation slot. 
  • First half of 2025 - Formal consultation, including indicative cost allocations. 
  • First half of 2025 - Begin engagement on site works e.g. cultural/environmental inputs. This is expected to span several months.  
  • Mid 2025 - Submit capex proposal to the Commerce Commission.  
  • End of 2025 - Commerce Commission decision on recovery of expenditure.  
  • End of 2025 - Enter into a full contract with the cable supplier. 
  • Mid to late 2029 - Cable manufacture begins (indicative next manufacturing slot available).  
  • Early 2030s - Install/commission new cables. 

Project Information and Consultation August 2024 

In August 2024 Transpower published an Information and Consultation paper about upgrading and enhancing the capacity of the submarine cables. 

Submissions in full: 

In this project


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