Blackouts are a small possibility if further outages occur at a major central Queensland power station during the height of a heatwave, according to energy experts.
The Callide Power Station was fully offline for several hours on Friday, leading to concerns from Queensland's opposition supply and prices could be impacted.
"If generators fail, there is no doubt that it will impact supply and prices if there's a heatwave over summer," LNP Energy Spokesman Pat Weir said.
But the government was adamant there was enough supply to meet demand, with energy minister Mick de Brenni on Monday saying demand across the state was sitting at 5500MW, whereas supply was 9960MW.
"Circumstances can change, but the system is healthy and manageable," Mr de Brenni said.
But energy policy lead at think tank the Australia Institute Dan Cass said it was "conceivable" that blackouts could occur under the right conditions.
What happened at Callide?
The four units at Callide Power Station near Biloela were all not operating on Friday after a series of incidents.
The B1 unit was brought back online Friday afternoon, B2 is expected back this week, while C3 is expected back later this month.
The C4 unit has been offline since an explosion in May last year that cut power to about half a million homes and businesses across Queensland and northern New South Wales.
The Mining and Energy Union has blamed maintenance issues on some of the recent outages, but CS Energy CEO Andrew Bills defended the maintenance program, saying the organisation "absolutely" follows it "to the letter".
Will this impact energy supply over summer?
Mr Cass said from the institute's research, the Callide Power Station ranked as one of the worst performing gas or coal fire power stations in the country by the number of breakdowns.
"When everything is going well [at a coal fire power station unit], that's 700MW of power ready to be used, but when they break down, there is a lot of power lost straight away," he said.
"It is conceivable that Queensland could face blackouts in the summer as a result of weakness in the energy system from outages at Callide, and I'm sure [the Australian Energy Market Operator] will do some analysis.
"But the hope is that the outages are rare, and other power stations are operating at or near capacity, and the interstate interconnectors are working at or near capacity."
He said if all that happened, a large state like Queensland, which has a lot of government ownership of the grid, could weather the storm.
"But it is a risk and people need to be clear eyed about this."
Mr Cass said in its 2022 Electricity Statement of Opportunities, AEMO predicted there would be no unserved energy, or customer demand that cannot be supplied within a region due to a shortage of generation, in Queensland until 2025.
"But the caveat, of course, is they're assuming there are no one-in-50-year events. And as we know from recent years, coal power stations are the kind of places you would look if you're worried about a one-in-50-year event," he said.
"AEMO's own projection is that the risk of a real unreliability in Queensland is in the realm of 2 per cent. It's small, but it's certainly not zero."
Grattan Institute energy program director Tony Wood said you could "never say never" to similar incidents occurring again.
"But I've not heard anything to suggest that this is suggesting some sort of systemic failure of the overall Callide Power Station," he said.
"It sounds like there have been frustrating, annoying combinations of circumstances, but sometimes that happens.
"The evidence we've seen so far suggests that's all it is, and I wouldn't trivialise it, but there is no reason to think that we're looking down the barrel of some really nasty summer problems."
Earlier this year, the National Electricity Market, or NEM, was suspended by AEMO as the market was impacted by several factors, including some coal generators being out of action due to unplanned events.
This led to fears of blackouts across a lot of the market, which takes in every Australian state and territory except Western Australia and the Northern Territory.
"If we had another combination of things also go wrong, as well as Callide, like the flooding of coal mines [that supply the power stations], or something like that, then yes, that would be more of a problem," Mr Wood said.
"But by itself, it's not an issue. It's a combination that makes a difference."
Mr Wood said he believed the incidents at Callide showed why there was a need "to step up the activities associated with the energy transition".
"It's more than just building more solar and wind farms," he said.
"It's also making sure that we've got the infrastructure in place to back up wind and solar."
