Residents in parts of eastern Australia face the prospect of blackouts as people reach for their air conditioners in predicted hot weather during a period of planned coal-plant outages.
The Australian Energy Market Operator (AEMO) issued a warning on Monday about blackout risks in NSW on Tuesday afternoon and Wednesday when temperatures are set to soar to 40C in parts of Sydney.
The operator warned electricity supply in Queensland could also be at risk on Wednesday, although it stopped short of warning of potential outages there.
Increased air-conditioning use and generator repairs at three NSW coal-fired power plants threaten to shut down the grid in some areas.
"High temperatures and strong electricity demand, combined with some generation outages, are causing tight electricity supply forecasts in NSW tomorrow and Wednesday afternoon," a spokeswoman for the operator said.
The energy operator warned electricity supply in Queensland could also be at risk on Wednesday. (Diego Fedele/AAP PHOTOS)
The operator is asking energy companies to switch off big electricity users and boost supply across the state.
"AEMO has alerted the energy industry and is working with power station operators and transmission businesses to boost electricity availability," the spokeswoman said.
"If a market response remains inadequate, AEMO will take actions available to maintain supply."
NSW Energy Minister Penny Sharpe said people should look out for each other during the heat spike and the government was keeping an eye out for any energy-supply problems.
"You should drink water, you should check in on neighbours and you should think about whether you need to walk out in the middle of the day in the beating hot sun," she said.
"Do you really need to have every single light on in the house ... do you need to have your air conditioning down at 19 degrees, you don't."
The Bureau of Meteorology on Monday enacted a heatwave warning in NSW and Queensland that is due to last until midweek.
The temperature in the Sydney city centre is forecast to peak at 33C on Wednesday, while in the northwestern suburbs it could reach 40C.
The predictions follow a week of soaring temperatures in Victoria, where parts of Melbourne reached 37C, well above the November average.