The country is waking to a bitterly cold morning with temperatures dropping as low as -6C in some areas overnight amid threats of power cuts.

Meanwhile, group representing big industry is warning that appeals to conserve electricity will become more common.

Electricity grid operator Transpower on Thursday warned the low temperatures could see power cuts occur if electricity demands spiked too high, particularly between the hours of 7am and 9am.

Follow our live updates here:

Businesses are asked to help and the Major Electricity Users' Group says industry starting cutting back production on Thursday, which has provided some relief.

The group's chair John Harbord says they have moved quickly to help shore up supply.

"So already we're no longer looking at a shortage of 22 megawatts, we're looking at a surplus of supply of 33 megawatts."

In addition to that, there are 243 megawatts of electricity "sitting in reserve", he says, though he warns that doens't mean people can be complacent.

John says appeals for people to conserve power are going to become more common.

"As we become even more reliant on intermittent renewable electricity generation like wind and solar... these types of scenarios become more likely."

John says a balance needs to be struck between renewable energy sources and thermal generation.

It's the third time this month Transpower has issued a notice about low power supply but the first time it has put out a warning for the public to cut back on power usage.