She said the power-saving measures were voluntary for households but “every little bit helps”. She added that households should use as much energy as they needed before 3pm because the grid had plentiful solar power until then.

“Solar is going gangbusters at the moment so if you’ve got air-conditioning, go for it as hard as possible and cool down the house before you get home tonight,” Sharpe said.

“If you can, we’re asking that if you get home and you need to use your air-conditioning, that is totally fine, but if you can turn it up a couple of degrees, that makes a big difference in terms of demand.”

The spring heatwave is Sydney’s most severe since November 2020, when the hottest day was 43 degrees at Sydney Airport. It is less severe in other parts of the state.

Globally, 2024 is on track to be the hottest year on record, breaking the previous record set only a year ago.

Sharpe said the problem with electricity shortages was caused by ageing coal infrastructure and heatwaves occurring earlier in the year.

Of the four power-generation units offline on Wednesday, two were unscheduled outages and two were planned maintenance to prepare for summer.

“We’ve got coal-fired power, which is still extremely important in NSW and it’s why we have looked at and agreed to the extension of Eraring, but they are also old kit,” Sharpe said. “They’re old plants, and they do have outages – that’s what causes some of the instability that we’ve got.”

Sharpe said coal power had already decreased from 80 per cent of NSW’s power generation to 50 per cent. She said blackout warnings would decrease over the next three to five years as the transition continued because the state was adding new electricity generation from both renewable sources and gas, as well as projects such as the Waratah Super Battery.

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Minns added that the energy transition was “not really an ideological question” because ageing coal-fired plants needed to be replaced anyway.

Minns said climate change made it harder for utilities to plan their maintenance and repair program so they are ready for the peak summer or winter period.

“The shoulder seasons are generally when most of the maintenance takes place, but increasingly, you’ll see heat wave conditions earlier and earlier in the year, and, obviously, we have to manage that,” Minns said.

AEMO said in a statement it was urging all available generation and all available powerlines to return to service, and was looking to procure additional reserves.

The regulator is negotiating with large power users, such as smelters and factories, which can be paid to reduce energy use so that blackouts are not triggered for households.

If AEMO cannot secure an agreement, it may be forced to intervene in the market to cut energy use.

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