File photo. Photo: 123rf
Transpower says power supply is tight, but comfortable, after a freezing night across much of the country.
Transpower had put out a notice warning power companies they may be unable to meet demand if there are any unexpected failures in the North Island between 7.30am and 9am on Friday.
The customer advice notice, posted on its website on Thursday, warned firms there was only a small surplus of generated power within that timeframe.
NIWA said last night was forecast to be one of the coldest overall nights of the winter nationwide.
State Highway 1 Desert Road was closed due to snow and ice.
Metservice Meteorologist Mmathapelo Makgabutlane said it was a cold start to the day, with the biggest chill in the South.
"Many places were well below 0 [degrees]."
She said some of the coldest places overnight were St. Arnaud at -6.7C, Mt Cook at -6.6C and the Lewis Pass at -6.3C.
But the North Island was not exempt. Palmerston North dropped to -1.1C overnight and Taupo to -0.7C.
Makgabutlane said even more chilly temperatures were expected for the North Island on Saturday.
Masterton and the Wairarapa were expected to start the day at around -4C, Hastings and the Hawkes Bay -2C and Taupo and the central North Island -3C.
In a statement to Morning Report, a Transpower spokesperson said its notice was mostly operational and the industry had responded to its call.
While power supply was tight early this morning, it was comfortable, the spokesperson said.
Mercury general manager Phil Gibson told Morning Report the demand on Friday morning was shaping up to be one of the highest this winter, and close to one of the largest on record.
"It's shaping up to be a reasonably firm peak this morning, one of the largest this winter, close to one of the largest on record" - Mercury general manager Phil Gibson
In cases like these, it was prudent Transpower made sure the sector had enough notice to be ready, Gibson said.
"If you think about the resilience of a power system, you need to know you've got redundant assets ready to go when the ones that are running may fail for some reason - that's the nature of power systems.
"You've got power lines and transformers and generators all around the country, some of those may not work all the time, so you need to know you've got back up.
"Then when you get to really high demand period, obviously most of that generation is expected to be running, so your buffer is less, so you need to know what you've got, you need to know you've got some reliable assets that will come on if you need them, but you can't have a hope strategy so you've got to use these notices that Transpower do really well to co-ordinate the sector, make sure everybody knows what's going on, is informed and can make the best decisions they can."
Mercury had its bases covered with a range of assets wind and geothermal as well as the Waikato hydro scheme, Gibson said.
"So for us, it's reasonably a easy task but for others that run thermal plants, they need to be able to start those assets and get them going, and I think that's actually a really important thing for the country to reflect on - just how important that thermal support is to making sure we can all have our toast and tea in the morning."
There was debate on how power generation would be sustainable as the population and economy grew, Gibson said.
"We've had some discussions this week in media about increasing renewables in pursuit higher and higher percentages of renewable electricity, but I think we need to make sure that we understand those assets that do make sure customers don't need to panic on mornings like this, that customers should just go about their day and the magic should just happen in the background."