Pre-cooling your house before the peak: when it pays in South East Queensland this summer

On a summer evening the air-conditioner starts on a house that has been soaking up heat all day, and on a time-of-use plan those are the dearest hours of the day to run it. Pre-cooling moves some of that work into earlier hours that cost less. And this is the first summer with the Solar Sharer Offer, which has been available since 1 July 2026, so for some homes those earlier hours now cost nothing. Whether it saves you money comes down to two things: your plan, and how well your house holds the cool.

What pre-cooling means

You run the air-conditioner in the late morning or early afternoon, bring the rooms you will use that evening down to temperature, shut the blinds and doors, and let the house coast. When the peak starts, the unit has less heat to remove, so it runs for less of the evening. The Australian Government's own Solar Sharer page suggests exactly this: heat or cool your home during the free period so you use less electricity later in the day.

When does pre-cooling save money

When your plan charges much less in the middle of the day than in the evening. The bigger the gap, the more it pays.

• On a Solar Sharer plan, grid electricity between 11am and 2pm is free in South East Queensland, capped at 24 kWh a day. An air-conditioner run in those hours costs nothing for the energy it uses. You still pay the daily supply charge and for everything outside the window, so the plan has to come out ahead over the whole day, not just the three free hours. Our Solar Sharer guide goes through who that suits.
• On a time-of-use plan, pre-cooling moves cooling out of the peak rate and into a cheaper one. The Queensland Government notes that some time-of-use plans have their cheapest rate during the day, which is the version that suits pre-cooling best.
• On a demand tariff, the charge depends on how fast you draw power at your busiest point in the peak window, not only on how much you use. An air-conditioner starting from a hot house at five can be what sets it, so pre-cooling can bring the charge down as well. See what a demand tariff is.
• On a single-rate plan, a kilowatt-hour costs the same at noon as at six. Pre-cooling does not make the cooling cheaper, and cooling through the hottest part of the day can mean the unit runs for longer overall. Comfort is the reason to do it, not the bill.

The peak itself is usually 4pm to 9pm in South East Queensland, the window the Queensland Government gives for peak demand, but your plan's own terms set the exact hours. Is a time-of-use plan worth it has more on the windows.

Will the house hold the cool until the peak

This is the half people skip. Pre-cooling only works if the cool is still there at five. The government's Your Home guide calls insulation critical to keeping a house cool, names windows as the main source of heat gain (especially east and west glass in the morning and afternoon sun), and warns that badly positioned thermal mass heats up and radiates heat well into the night. A brick wall that has been in the sun all afternoon keeps warming the room after the air-conditioner stops.

A well insulated house with shaded windows and the blinds down can stay comfortable for hours. An uninsulated house with big west-facing windows can be back where it started before the peak, and then the evening run is as long as it ever was. You will know which one you live in after a week of trying it.

How to get the most from it

• Close doors, windows, curtains and blinds in the rooms you are cooling, so the cool air stays in.
• Cool the rooms you will use in the evening, not the whole house.
• In the evening, set the unit between 24°C and 26°C. The Queensland Government says each extra degree of cooling can add around 5% to 10% to the electricity it uses.
• Use a fan alongside it. The energy.gov.au guide says a fan blowing on you makes it feel about 3°C cooler, for very little power.
• Clean the filters, and book a service before the hot months. energy.gov.au suggests servicing before peak use, such as in late spring, which is now.
• Put it on a timer. Nobody is home at 11am on a workday to switch it on, and the government's Solar Sharer advice is to use timers or smart settings so appliances run in the free window.

If heat makes a medical condition worse

Queensland has a separate concession for this. The Medical Cooling and Heating Electricity Concession Scheme helps with electricity costs for someone with a chronic condition made worse by changes in temperature, such as multiple sclerosis. The applicant needs a Pensioner Concession Card or a Health Care Card and must be responsible for paying the electricity bill, and a specialist fills in the medical section of the form. It is paid into your bank account rather than through your retailer, so changing retailer does not affect it. It sits beside the Queensland Electricity Rebate, not instead of it.

How to tell whether it suits your house

Look at when you use power, not only how much. A bill shows totals; a smart meter data file from your retailer's online account shows every half hour, so you can see how much of a summer day lands between four and nine. If a big share does, you have the most to gain. Then price the plans twice: once as you use power now, and once with the cooling moved into the middle of the day. If a time-of-use or Solar Sharer plan only wins the second way, the saving depends on the timer running all summer, and you should know that before you switch.