There's still uncertainty over how Southland's economy will absorb the loss of nearly 2,600 jobs.

Rio Tinto is to wind up its operation in August 2021, citing high power costs and a poor outlook for the industry.

Prime Minister Jacinda Ardern told Mike Hosking the Government will spend $25 million upgrading the Homer Tunnel - which should create 180 local jobs.

But she says no one industry can save all the smelter's workers.

"14 months isn't enough time for the kind of longer term projects which are likely to provide will provide long time income, but there are plenty of prospects in the region."

Ardern says many of the skilled workers at the Tiwai Point smelter are actually tradespeople, who can put their skills to good use.

In Northland, Marsden Point Oil Refinery is scaling back operations, and looking at changing to an import terminal rather than processing crude oil into fuels.

Prime Minister Jacinda Ardern says there's still value in keeping the refinery running.

'We need to continue importing oil and there's a range of other things going on and interests for NZ having the refinery."

Refining New Zealand has ruled out shutting the plant completely.