National grid operator Transpower warned yesterday that there could be insufficient supply between 7am and 9am today.
It asked people to reduce their use of power by turning off heaters and lights in unused rooms, delaying using appliances, and not charging devices and cars.
The Major Electricity Users' Group (MEUG), which represents big industry, said the sector had freed up about 60 megawatts of power in response.
While those savings would hit production in the short-term, the group's chair, John Harbord, said that was what they signed up for as responsible New Zealanders.
Despite overnight temperatures dropping well below zero in some areas of the country, New Zealand had managed to save over 260MW, Transpower's executive general manager Chantelle Bramley told RNZ's Morning Report programme today.
That represented "a very significant response", she said.
"As you know, the situation was very tight; we've had really cold weather. We just want to thank New Zealanders for their fantastic response this morning, it has made a huge difference getting us through the morning peak."
"We've seen over 260 megawatts of response, that's the equivalent to a very large generator and that made up the shortfall that we were concerned about."
The savings represented "a very significant response", she said. "Thank you to everybody that did their bit."
"The networks were working really hard to manage load... and we've avoided any further need to switch off supply."
Harbord told Morning Report the group had two concerns around the wider issue of electricity supply and demand: One was that there was not a strong argument for spending millions of dollars on a new plant if it sat unused apart from times of big demand.
The other was the mix of electricity generation; as there was more reliance on renewables, such as solar and wind, situations such as today's could arise more often, he said.
"A bit more thermal peaking would be really helpful, because the thermal sits there, you can stockpile gas and coal and turn it on almost in an instant and the problem we have with solar and wind, you can't stockpile it and save it for when you need it."
In 2021, almost 34,000 households lost power on one of the coldest nights of the year, as insufficient supplies were arranged for the surge in demand.
An industry panel fined Transpower $150,000 for its role in the blackouts.
'Unusually cold' start to May
MetService had forecast temperatures to plunge overnight on Thursday. Meteorologist John Law told RNZ's Morning Report programme it was an unusually chilly start to May.
"Looking at some places like Christchurch, for example, down to minus 6.3 Celsius last night. That's unusually cold for any night in May... that air coming up from the south.
"Then, of course, there's these nice clear skies we've had in the last few nights allowing any of that daytime heat to dissipate once the sun sets."
At 7am, southern cities Dunedin and Invercargill were on 10°C. The warmest place was Kaitaia in the Far North on 11.7°, while the coldest was Omarama in South Canterbury on -6.7°.
'This is not where we want consumers to be'
Energy Minister Simeon Brown told Morning Report his expectation was that generators and regulators (Transpower and the Electricity Authority) would have had security of supply as a top priority going into winter.
"We've had a number of winters where there has been tightness in recent years and there has been changes made around how information is shared, how decisions are made, how warnings are provided to ensure that the market and the system operates as best possible for consumers.
"But ultimately, this is not where we want consumers to be with these types of warnings. We ultimately want a secure, reliable electricity system where Kiwis are able to stay warm and the light in winter time."
Transpower has said the problem with supply was due to 700MW of generation being offline due to maintenance.
But Brown said "part of the reason" for the squeeze was that New Zealand had "old thermal generators, which means when we have to turn it on, some of it's not always available".
He also blamed the previous government's ban on new gas exploration, the "frankly impossible" 2030 100 percent renewable target and the Lake Onslow battery scheme, which he said had had a "chilling effect" on new investment from the market.
The Labour Party's energy spokesperson, Megan Woods rejected that, telling Morning Report the country needed ways to store electricity.
The Lake Onslow battery scheme would have done that, she said, but the coalition government had ditched it and had no plans for other storage options.
Supply expected to hold up
Transpower's Chantelle Bramley said the grid operator was not concerned about any further supply issues at this stage.
"We're expecting pressure to drop off later this afternoon; we're not looking at any potential issues over the coming days."
The 700MW that were currently offline due to maintenance were due to come back online over the next few weeks, she said.
May was always a challenging month with lots of outages, Bramley acknowledged, but she said generators had done an amazing job ensuring there was as much supply as possible available this morning.
The timing of future maintenance would be looked at she said, but investment in the system was also necessary to make sure there were enough flexible resources to be able to respond to unseasonably cold days.
