The first of two major electricity hearings being held this week is now under way.
The Electricity Commission is hearing oral submissions on Monday to decide which of New Zealand's electricity generators will pay for Transpower's $728 million upgrade of the Cook Strait cable.
The project would install extensive new equipment at Benmore and Haywards and increase the cable's capacity to 1200 megawatts.
South Island generators, especially Meridian, have sought the hearing after battling the decision to levy the cost of the project mainly on them.
The Electricity Commissioner told those present that Monday's discussion would only consider whether the upgrade would be a good investment, and not who would pay for it.
The major electricity users group did not attend the hearing, saying the written submission offered nothing new on the long-running issue.
On Thursday, New Zealand's third biggest electricity company, Genesis, opens its resource consent application for a 480-megawatt power station at Rodney, north of Auckland.
This will be heard by independent commissioners on behalf of Rodney District and Auckland Regional councils.