What Temperature Should You Set Your Air Conditioner?
You set a target temperature of 23°C.
Minutes later, you raise it to 24°C. That 1°C increase may seem minor, but it makes a big difference in the air conditioner’s energy consumption. Generally, for every 1°C increase in the target temperature, an AC’s energy usage drops by 5–10%.
For homeowners in Australia, even slight AC temperature increases can result in significant energy savings. Saving on your energy bills doesn’t mean you shouldn’t feel comfortable in your home, though. You just need to know the best AC temperature for different times of the day and find practical ways to reduce costs without sacrificing comfort.
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Understanding How Your Air Conditioner Maintains Temperature
How the set temperature works
When an air conditioner runs, it’s constantly pulling air from and releasing air into the room. It uses temperature sensors inside the indoor unit to measure the temperature of the “return air”. The return air is the air being pulled back into the AC to be cooled again. The AC’s goal is to match the return air temperature with the set or target temperature.
Once the sensors tell the AC that the return air has reached the set temperature, it temporarily stops the cooling cycle. As soon as the sensors detect the return air temperature rising above the target temperature again, the AC restarts the cooling cycle.
The sequence we just described is what happens inside non-inverter air conditioners. If you’re using one, you may hear its intermittent “grunts” as it cycles on and off. You may also have noticed temporary rises and drops in indoor temperature while the AC is running.
Modern inverter air conditioners also use temperature sensors to detect the return air temperature. But instead of stopping when the target temperature has been reached, they slow down and keep running at a lower output. This helps the system maintain a steadier room temperature without using full power all the time.
How wide should the difference between the target and the outdoor temperature be?
Setting the thermostat very low won’t help the AC cool the room any faster. It’s actually counterintuitive. The AC reads your target and starts working hard to reach it, consuming more energy than it would’ve if the target were more realistic. And despite its efforts, it may still not succeed in meeting the target.
As a general guide, aim for a target temperature that’s around 8°C lower than the outdoor temperature. On a 34°C day, that means you should set your air conditioner close to 26°C rather than pushing it down to 20°C or 16°C. Please keep in mind that this is a guide, not a strict rule.
Best AC Temperature for Different Situations
Your current activity, the time of the day, and how long you're spending in a space all determine the best AC temperature at that point in time.
Many Australian homeowners use settings of 25°C and 27°C during the day. You can move out of this range and go lower when you’re asleep or the air is really humid. You can also go higher when nobody’s home.
| Situation | Suggested AC Setting | Why We Recommend It |
| Home during the day | 25°C–27°C | Good balance between comfort and running costs for many Australian homes. |
| Away from home | Around 28°C–30°C, or higher if the home will be empty for hours | Reduces cooling an empty space without letting the house heat up too much. |
| Sleeping | Around 24°C–26°C for energy-efficient cooling | Keeps the room comfortable without overcooling overnight. |
| Humid weather | Around 23°C–25°C, or use dry mode when suitable | Helps the system remove moisture without pushing the temperature too low. |
Please don’t rely on the AC alone for nighttime cooling, especially when you’re ready for bed.
A range of 24°C to 26°C may be energy efficient but it may not be cool enough. We aren’t saying so; science is. In one 2020 Sydney summer field study, participants who slept in warmer bedrooms couldn’t fall asleep easily. And when they finally did, they couldn’t get as much deep sleep as those in cooler sleeping environments.
The solution? Add a fan. Researchers from the University of Sydney found that using fans can “raise the temperature threshold” by 3°C–4°C. What this means is, if you leave the AC in the 24°C–25°C range and turn on the fan, you’ll feel as comfortable as you’d have felt if the AC temperature were set to 21°C or 20°C.
How to Reduce Energy Costs Without Sacrificing Comfort
Much of the heat your AC works so hard to remove comes from outdoor air, sunlight z and indoor heat sources such as ovens, bulbs and appliances.
To keep it out, try these fixes.
- Close blinds and curtains: Windows and glass doors can let in a large amount of unwanted heat, especially when direct sunlight hits the glass. Ensure all blinds and curtains are closed all day long, especially those on east- and west-facing windows and doors, before the sun rises.
- Choose heat-blocking window coverings: Use thermal-backed curtains, honeycomb blinds and external shading to reduce heat gain through windows. External shade is especially useful because it blocks sunlight before it reaches the glass.
- Prevent air leaks: Use draught excluders or weather seals to seal up gaps around doors and windows. This helps prevent hot outdoor air from entering through these areas and stops the conditioned indoor air from escaping.
- Limit how often you use heat-generating appliances: Ovens, dryers, stovetops and other appliances can release heat into the indoor air, increasing the cooling load your AC has to remove. Use them earlier in the morning or later in the evening where possible, especially during very hot weather. Also, switch off any lights left on unnecessarily.
Running a ceiling fan alongside your air conditioner can help the room feel 3°C to 4°C cooler. Remember the University of Sydney research we talked about earlier?
If you’re on a time-of-use electricity tariff, try not to use your AC peak periods, when electricity costs more. These periods vary from retailer to retailer. Check your contract to know what time frames your energy retailer deems peak periods.
If your home is well insulated, you can pre-cool it earlier in the day, then raise the AC temperature during peak hours.
When the outdoor temperature drops in the evening, switch off the AC and open windows if it’s cooler outside than it is inside. Cooler air will circulate throughout the home, and you won’t have to run your AC for longer than necessary.
A programmable thermostat adjusts the AC temperature based on a schedule you set, while a smart thermostat uses geofencing and occupancy sensing features to automatically detect when you leave home and when you return.
With either option, you can raise the AC temperature while you are away to reduce energy use. You can also schedule the temperature to drop shortly before you return, so the room feels comfortable when you get home.
The difference is that a programmable thermostat has to be programmed, meaning you need to tell it what to do and when. Meanwhile, over time, a smart thermostat can learn your routine and make some temperature adjustments automatically. It may also allow you to control your AC temperature from your phone.
Keep Your AC Working Efficiently
Consistently setting your AC to ideal temperatures goes a long way, but it can’t help much if the air filter is dirty or vents and return air grilles are blocked. Clean or replace the air filter as the manufacturer recommends.
Arrange cabinets and large furniture so they don’t sit directly in front of vents or return air grilles, and keep both airflow openings clear of dust.
Getting Professional Assistance
If your AC struggles to reach the set temperature, cycles on and off too often, blows warm air, makes unusual noises or causes a sudden increase in your power bills, that may be your sign to contact a licensed professional for an AC inspection.
BG Electrical & Air Con can inspect your air conditioner and identify the cause of the problem and recommend the best solution. We’ve been serving the Brisbane community for more than a decade. Contact us for a free onsite quote tailored to your needs.