The government should stop focusing on unproven hydrogen energy technology to tackle climate change, says an expert.
Canterbury University professor of mechanical engineering Susan Krumdieck said the government was enthusiastic about the development of green hydrogen, but it was a waste of time and money.
Green hydrogen is a potential future vehicle fuel that would be produced by the electrolysis of water using renewable electricity, and has been touted for its potential to help reduce carbon emissions.
Krumdieck said a national energy strategy was needed.
Proven technologies could be used to meet New Zealand's zero carbon goal by 2050 - and address transport needs at the same time, she said.
Energy Minister Megan Woods has said green hydrogen production could be a replacement industry after the Tiwai aluminium smelter is closed.
Manapōuri hydroelectric power station was built to support Tiwai smelter, which is the largest single consumer of power.
Krumdieck said surplus energy from Manapouri should be used to develop a national transport system starting from Invercargill and extending throughout the South Island, before crossing Cook Strait.
KiwiRail could be a key part of the development, which would provide thousands of jobs.
"The South Island becomes a net zero (carbon) island, one of the first ones in the world," Krumdieck said.
Her students have been working on a plan for a national rollout, which meets goals for sustainable cities.
"We have the capability in New Zealand to beef up our rail engineering and our power electric power engineering for transport."
She said it would take about 10 years to electrify the South Island's transport network.
Krumdieck said her students would be releasing more details about the plan later this month.