The best temperature for your air conditioner

What temperature should I set my air conditioner in summer in Australia?

25 to 27°C. That is the federal government's advice on energy.gov.au, and it is where a modern inverter split runs cheaply and quietly for hours. The NSW Government's own advice is a touch cooler at 24 to 26°C, so if 25 feels warm in a humid Sydney summer, 24 is a defensible floor.

On the humid coast, Brisbane, the Gold Coast, Sydney on a sticky February night, 25°C with the air dried out feels cooler than 23°C with the air still damp. Humidity is what makes a room feel close. If the room reads 25 and still feels muggy, drop the fan speed a notch so the air spends longer over the cold coil, or try dry mode on mild humid days. Our guide to air conditioner modes and symbols explains the difference.

In dry heat, Perth, Adelaide and inland, 26 or 27°C with a ceiling fan running is comfortable for most people. Moving air across your skin makes a room feel a few degrees cooler than the thermostat says, and the fan costs a couple of cents an hour.

What temperature should I set my air conditioner in winter?

18 to 20°C. Again that is the energy.gov.au range. Reverse cycle heating is the cheapest heating most Australian homes can run, and it stays that way as long as you are not asking for a tropical lounge room in July.

Two quirks catch people out in heat mode. The unit may blow cool or nothing at all for the first few minutes while it warms the indoor coil, and it will pause now and then to defrost the outdoor unit on cold mornings. Both are normal. The other quirk is height. Warm air pools at the ceiling, and the sensor in a wall-mounted head sits up there with it. Point the louvres down in heat mode and the room will feel warmer at the same setting. If it still cannot hold 20°C on a cold morning, it may be undersized or tired, and a local quote will tell you what a replacement costs.

Best air conditioner settings for summer and winter

Which is colder, 24°C or 16°C on an air conditioner?

16°C is the colder setting. It is also almost never the right one.

The number on the remote is a target, not a blast setting. Set 16°C in a 32°C room and the unit runs flat out until the room reaches 16°C, which on a hot day it probably never will. The air coming out of the vents is not much colder than it would be at 24°C; the compressor just never gets told to ease off. You pay for hours of maximum output to overshoot the temperature you actually wanted.

If the room is hot when you walk in, set 24 or 25°C and use turbo or powerful mode for 15 minutes. That gets the pull-down speed without leaving the target at 16.

Is 22 degrees cold for aircon? Is 23 degrees too hot for a house?

22°C is on the cool side for summer cooling. Most people are comfortable at 24 to 26°C once the humidity is down, and 22°C costs roughly 15 to 30% more to hold than 25°C, going by the 5 to 10% per degree rule.

23°C is not too hot for a house in summer. It is cooler than the official 25 to 27°C range. In winter, 23°C is warmer than it needs to be; 19 to 20°C with socks on will cost noticeably less.

Comfort is personal. Babies, older people and anyone unwell may need different settings, so follow their doctor's or carer's advice over any energy rule of thumb.

What is the best temperature to keep your AC on at night?

25 to 27°C in summer with sleep mode on. Your body temperature drops as you sleep, so the room can warm a degree or two over the night without waking you. Sleep mode does exactly that, and it runs the fan at its quietest.

In winter, the cheapest answer is off, with the timer bringing heat on half an hour before you get up. energy.gov.au's own winter advice is to turn heating off overnight. If you need it on, 16 to 18°C is plenty under a doona.

Bedroom units are usually 2.5 kW, and a 2.5 kW inverter at night typically draws well under half a kilowatt. At a 2026 flat rate of around 33 cents per kWh that is roughly 13 cents an hour. Eight hours is about a dollar. The running cost calculator will do your exact numbers.

Is it cheaper to run the aircon all day or just when you need it?

Just when you need it, for anything longer than a few hours away. Holding an empty house at 25°C through a 38°C afternoon uses more electricity than cooling it down when you get home. The inverter's pull-down burst is short; eight hours of holding is not.

The two exceptions are time-of-use tariffs and solar. If your peak rate starts at 3 or 4 pm, pre-cooling in the early afternoon and coasting into the peak can cost less than switching on at 5 pm. If you have panels, run it while they produce. Our running costs guide has the per-hour numbers for every size and the 2026–27 tariffs.

You may have heard of the "20 degree rule" and the "7 degree rule". Both are American thermostat rules written in Fahrenheit. We translate them in our air conditioner rules of thumb guide.

When the temperature setting is not the problem

If you are at 25°C and the room never gets there, the unit is working hard to tell you something.

• Filters. A clogged indoor filter chokes airflow. Clean it every few weeks in summer.
• Size. A 2.5 kW unit in a 35 m² open-plan room will run flat out and lose. Run the room through the size calculator, then get up to three local quotes for the right size.
• Sun. West-facing glass on a February afternoon is a heater you did not buy. Shade it from outside.
• Doors. A split sized for the lounge cannot cool the hallway, the kitchen and the stairwell as well.
• Age. A non-inverter unit from the early 2000s may simply be tired. A new bedroom split is usually $1,500 to $2,500 installed in 2026 (see split system costs). If yours is past 10 to 15 years and struggling, get up to three licensed installers to look at it and price a replacement.