The Liddell Power Station has reached the end of its life, after helping light New South Wales for more than half a century.
This week the remaining three turbines at the coal-fired plant in the Upper Hunter will spin for the last time, with the final generator due to shut on Friday.
So, how will the grid cope with the loss of the station?
Will the closure leave NSW short of power?
Liddell's closure has been a long time coming, with AGL announcing plans to wind up the plant in 2015.
That's meant the energy network has had plenty of time to prepare for a smooth transition.
The first of Liddell's four generators was switched off permanently last April.
"Units have been withdrawn to the point at which it hasn't been a significant source of electricity production in New South Wales for really the last 18 months," Bruce Mountain, an energy economist at Victoria University, said.
For context, Liddell produces a small portion of the electricity generated in NSW.
The plant was registered to produce 1,500 megawatts — with three turbines running — but it has been operating below capacity.
"It's been putting around 600 megawatts into the markets," Professor Mountain said.
That's if it is producing. The ageing station has kept breaking down.
NSW has the capacity to generate 19,890 megawatts, according to the Australian Energy Market Operator (AEMO).
If the plant were to produce its current theoretical capacity of 1,500 megawatts, its output would amount to 7.5 per cent of the state's generation capacity.
To make up for the shortfall, however small, other generators must work harder.
"There is still plenty of NSW coal generation capacity," Professor Mountain said.
"Much of it is not highly used," he said.
Is there a risk of blackouts?
Professor Mountain said if capacity remains available and no outages occur during winter's peak, the state should avoid blackouts.
AEMO, which last year ordered generators to produce power amid forecast shortages, appears unconcerned about Liddell's closure.
"The notification of Liddell's retirement has allowed the market to respond, with NSW forecast to meet reliability measures until at least 2025," AEMO's executive general manager of system design Merryn York said.
The market operator is more worried about the slated 2025 closure of the Eraring Power Station, Australia's largest coal-fired plant, at Lake Macquarie.
While the Waratah Super Battery Project aims to offset Eraring's production, AEMO forecasts gaps in supply from 2025.
To secure energy supply, Premier Chris Minns is open to the government buying the plant, which Origin Energy plans to shut seven years early.
The state's energy production is on track to fail the reliability standard in 2027-28, AEMO predicts, unless more generators open.
In 2029-30, the risk of energy shortages worsens, with the expected closure of a second plant at Lake Macquarie, the Vales Point Power Station.
"There remains an urgent need for additional commitments," AEMO warned in a February report.
The dominoes are falling in other states too, with Queensland's Callide and Victoria's Yallourn coal-fired plants due to shut in 2028.
How will Liddell's closure affect energy prices?
Professor Mountain does not think the shutdown will push up power bills.
"[Liddell] was one of the more expensive but not the most expensive generator," Professor Mountain said.
"It wasn't a significant price setter during much of the time, and its production can be made up by running existing generators harder."
Professor Mountain said Liddell's retirement would leave a smaller gap in generation than that of Victoria's Hazelwood power station.
The latter's closure at five months' notice saw power prices hiked.
"I don't think the closure of [Liddell] is significant enough to imagine it's going to be a major price factor," Professor Mountain said.
"The regulators will be watching it like a hawk … and ready to pounce on AGL essentially, should it seek to withdraw capacity to take advantage of the constraints."
Simon Wright, a sustainability researcher at the University of Technology Sydney, said any volatility in the wake of the Liddell closure was likely to be short-lived.
"There's lots of new generation coming online," Dr Wright said.
"A lot of that capacity is coming from renewables … large scale solar, wind and, of course, the steady increase in household solar," he said.
"When the sun is shining, we're getting up to 35 to 45 per cent renewable energy generation in NSW."
In April and May last year, power prices surged to record highs, driven by the war in Ukraine.
This year's outlook is somewhat sunnier.
Contract prices for electricity are falling but are predicted to remain above 2021 levels for years to come, according to an Australian Energy Regulator (AER) report.
These are prices energy retailers pay generators and changes flow to consumers, albeit with a lag.
"It takes a few months for those lower prices to feed through to the market," Dr Wright said.
Why will power prices be higher in NSW and Queensland?
Contract prices are predicted to be higher in NSW and Queensland than in South Australia and Victoria.
"These contract prices indicated that participants might have been anticipating a market impact from the closure of Liddell power station in NSW," the AER report states.
But Professor Mountain said external factors would have a greater effect on bills than the closure of Liddell.
"We've seen international gas prices weaken a lot, and that's having a knock-on effect in our markets," Professor Mountain said.
"The underlying fundamentals, certainly for gas and to some degree also for coal, are much more favourable now than they were this time last year."
