Power companies have pleaded with residents and businesses to reduce their electricity consumption over the next few days as demand nears record levels.

They are urging Queenslanders to cut back on their air conditioning and even turn off the second fridge in the house as they scramble to cope with a sudden power supply shortfall.

Powerlink chief executive Paul Simshauser said a lack of generating capacity in Queensland had reduced supply and warned of “supply outages” in coming days.

“In the event of supply outages, it is important to note emergency services and other priority groups such as hospitals and nursing homes will be given priority access to electricity supply to ensure that crucial services are available,” he said.

“We appreciate the cooperation and patience of all Queenslanders while we manage this high demand event.”

By 4 pm on Tuesday, Energex was reporting more than 20,000 customers without power across Brisbane and the Gold and Sunshine Coasts, with Rochedale, Browns Plains, Inala and Woodridge the hardest hit as a severe thunderstorm swept through the area.

Queensland is forecast to reach an electricity peak demand later on Tuesday of 10,032 MW, very close to the 2019 record of 10,044MW and well above the 2021 peak of 9450MW.

Temperatures in some parts of Brisbane hit 35 degrees by 1pm on Tuesday, with forecasts suggesting the hot conditions will continue well into the evening. The hot, unusually humid conditions are expected to continue on Wednesday.

Mr Simshauser urged residents to turn off their second fridges and pool filters and run their home air conditioners “a couple of degrees higher” to reduce consumption.

“We’re encouraging electricity customers to reduce their energy consumption where safe to do so over the next two days,” he said.

“Your safety and wellbeing is important so only reduce energy consumption if it is safe to do so. We appreciate your efforts in reducing power use.

“By reducing electricity use at home and in your workplace, the community can help ensure that power system security is maintained in Queensland.

“Unfortunately Queensland has several large generators undergoing emergency maintenance which has reduced available supply.

“We will keep Queenslanders informed through our communication channels, and the media. I strongly encourage all Queenslanders to keep up to date and consider how you can help by reducing your electricity consumption to prevent outages.”

Premier Annastacia Palaszczuk briefly addressed the heatwave on Tuesday saying:“Think about your family, think about your neighbours and please try and stay as cool as you possibly can.”

Energy Minister Mick de Brenni said power companies were working to reduce demand, with big industrial users being asked to reduce their use during the peak expected this evening and tomorrow evening.

“While we are working with major electricity users to manage demand, households can also take simple steps to help like turning off devices that are on standby and other appliances where it is safe to do so during the evening peak,” he said.

“Essential services such as hospitals, transport networks, ports, airports and other key infrastructure will stay online.

The Australian Energy Market Operator earlier on Tuesday issued an LOR3 (lack of reserve) notice which it has since cancelled. An LOR3 signals that available electricity supply has outstripped demand and there are no reserve supplies available.

It is understood three coal-fired generators are currently offline, including the Callide C4 unit which exploded in May last year – cutting power to 400,000 homes and businesses – and is expected to take much of this year to fix.