On a warmish evening across Perth and southern Western Australia at the end of last month, Andy Wearmouth was fretting while just about everybody else was blissfully ignorant.
That evening, the body that runs WA's biggest and most important electricity system called on a few diesel-fuelled generators to fire up and feed some power into the grid.
Mr Wearmouth, who until 2017 was the chief engineer of state-owned power provider Synergy, said the implications of "dispatching" such back-up diesel plants were clear.
"That says you're pretty much at the end," Mr Wearmouth said.
"There wasn't a lot [of generating capacity] left.
"The situation is not pretty. And we haven't really gone into the hottest part of summer."
Will the lights stay on over summer?
Amid forecasts of a hotter-than-average summer across WA's south, fears are growing about the health of the state's main power system and whether the lights will stay on over the coming months.
Mr Wearmouth acknowledged recent pressure on the system was being heightened by a series of outages that have hit some major, largely gas-fired plants.
But the 62-year-old said the signs were obvious that the grid was under stress amid the rapid decline of coal-fired power in the face of rising renewable energy output.
"I'm actually concerned," he said.
"This is probably the most fragile I've seen the power system since probably the late 90s.
"The issue is that power systems are amazingly robust things, but they will only take so much.
"And there seems to be a real confluence of things happening at the moment."
In June, the state announced it would close its two remaining coal-fired plants by 2029, leaving just one privately owned coal generator.
The decision came amid a deepening crisis in the coal hub of Collie, south of Perth, where one miner is in receivership and the other is struggling to stay afloat.
While turmoil in the coal industry is underlying many of the problems plaguing the system, observers note other factors are at play.
A number of the biggest gas plants are offline including a 335MW privately owned unit at Kwinana and Synergy's 250MW Cockburn and 118MW Pinjar turbines.
On top of this, a leak at a big offshore gas well in WA's northern waters has slashed production at the processing hub of Varanus Island, cutting supplies to the south of the state.
To add to the woes, plans by Synergy to switch on a large-scale battery at Kwinana by the end of the year are believed to be behind schedule, with commissioning now not likely until early 2023.
Minister confident lights will stay on
WA Energy Minister Bill Johnston said the timing of the so-called big battery project was within a "reasonable period of expected completion".
Mr Johnston said there "are always challenges" in managing the south west interconnected system, which he noted was one of the largest isolated electricity grids in the world.
However, he was confident the lights – and people's air conditioners – would stay on.
"There are always challenges in managing the West Australian electricity system because supplying one of the largest grids with a very low level of population is very complicated," Mr Johnston said.
"But it's well prepared for this summer."
According to the minister, Synergy was dealing with challenges to fuel supply by importing coal from New South Wales and ensuring gas storage levels were in good shape.
He also noted AEMO (Australian Energy Market Operator) had gone to the market seeking extra back-up reserves of energy from generators and big power users who could pare back demand at times when the grid was under strain.
"I'm not saying that there won't be individual outages for specific customers," he said.
"But in terms of the grid itself, it's ready for the summer."
Not everyone shares the minister's confidence.
'We're on a knife edge up until Christmas'
Liz Aitken runs renewable energy consultancy, Empire Carbon & Energy, from her home in Perth's eastern suburbs.
She said she had become so concerned about the state of the grid that she took matters into her own hands three years ago.
"That's part of the reason why I made the effort to install batteries and solar in my house back in 2019," Ms Aitken said.
"I did not want to be disconnected from the grid or have my power cut when I'm in the middle of an important Zoom meeting."
Last summer, when problems with the poles-and-wires network sparked rolling blackouts during an intense heatwave, she admits she was one of the lucky ones whose supplies were unaffected.
But casting her eyes forward, she's worried she might not be so lucky this time around.
"I believe we're on a knife edge up until Christmas," she said.
"Nothing can go wrong.
"We're just hanging in there at the moment.
"If we get a run of really hot days, if another plant falls over, I think we could find ourselves in a situation with blackouts fairly quickly."
Ms Aitken argued the government was being caught flat-footed by the rapid pace of change in the energy industry, calling for the transition away from fossil fuels towards renewable sources to be treated as an emergency.
Key to this, she said, was bringing online as quickly as feasible new sources of generation, storage and transmission needed to replace the retiring coal plants.
"We actually need to treat the energy transition as if it's an emergency in this state," she said.
"Other states are actually doing that now.
"We don't seem to be doing that and I'm concerned that will leave all of us in the lurch."
Hopes pinned on 'luck and fair weather'
Mr Wearmouth, who worked in the electricity industry for 35 years, agreed time was running out for the government to keep the power system on an even keel given the upheaval underway.
He said the state had to get a grip on coal supplies until they were no longer needed, while noting there was just seven years to build the replacement capacity required.
In the meantime, Mr Wearmouth said households and businesses in the south of the state were facing a white-knuckle ride this summer.
He said a run of hot weather or dose of bad luck could be enough to tip the system into disarray.
"With a bit of luck and fair weather, we'll scrape through," Mr Wearmouth said.
"[There] will be some very uncomfortable days, I suspect, for the people dispatching the plant and operating the market.
"But you might get through.
"I suspect you will only need one material plant failure that will probably bring you to a point where on certain days you don't have sufficient capacity, particularly if the wind isn't blowing.
"And that will obviously get very untidy."
