Best Temperature for Your Air Conditioner in Summer and Winter
The best temperature for your air conditioner is usually 24–26°C for cooling in summer and 18–20°C for heating in winter. These are energy-efficient starting points: adjust them to suit your comfort, the people in your home and the conditions in each room.
Turning the temperature to its lowest setting is rarely the best first response to a hot house. The right operating mode, clear airflow, window shading and a suitable system all affect how comfortable your home feels.
For Perth households, the aim is to find a setting that keeps occupied rooms comfortable without asking the air conditioner to cool or heat more than necessary.
Quick Summary
| When you’re using your air conditioner | Suggested starting point | What to consider |
|---|---|---|
| Summer cooling | 24–26°C in Cool mode | Sun exposure, airflow and personal comfort |
| Winter heating | 18–20°C in Heat mode | Draughts, clothing and room use |
| Overnight in summer | Start within the summer range and adjust for comfort | Bedding, airflow direction and timer settings |
| During very hot weather | Use a comfortable cooling setting and reduce incoming heat | A lower setpoint cannot compensate for every capacity or airflow problem |
The summer and winter ranges above align with NSW Government guidance for reverse-cycle air conditioners. They are efficiency recommendations, not a requirement to remain uncomfortable.
What Is the Best Air Conditioner Temperature in Summer?
Start at 25°C in Cool mode, then adjust gradually if needed. If you remain comfortable at 26°C, there is little reason to choose a colder setting.
Allow the room time to respond before changing the temperature again. Furniture, walls and floors can retain heat, so the room may take time to feel comfortable even after cool air starts flowing.
Before lowering the thermostat, check:
- Is the air conditioner set to Cool, rather than Fan or Heat?
- Are windows and external doors closed?
- Are blinds or curtains covering sun-exposed windows?
- Can air circulate freely around the indoor unit?
- Are you trying to cool more space than the system is designed to handle?
For example, a west-facing Perth living room may feel warmer in the afternoon than a shaded bedroom at the same thermostat setting. The living room receives more heat through its windows and surfaces. Lowering the setpoint alone does not address that incoming heat.
Shading the glass and improving air circulation may make the room more comfortable without another temperature adjustment.
What Temperature Should You Set Reverse-Cycle Heating to in Winter?
For winter heating, 18–20°C is a practical starting range. Select Heat mode, commonly shown by a sun symbol, and choose a setting that feels comfortable with normal winter clothing.
A higher number means a warmer target temperature. It does not necessarily mean the room will heat faster.
If the room still feels cold, look beyond the controller. Draughts around doors, uninsulated areas and poor air distribution can make a room uncomfortable even when the system is operating.
Keep furniture clear of outlets and follow your system’s instructions for directing warm air. In a ducted home, check that the rooms you are using are included in the active zones.
Avoid repeatedly switching between high and low settings. Choose a sensible target, give the system time to respond and make small adjustments.
What Is the Best Air Conditioner Temperature for Sleeping?
There is no single overnight setting that suits everyone. Bedding, clothing, room conditions and personal preferences all affect sleeping comfort.
During summer, start within the usual cooling range and adjust if you are too warm or cold. Consider airflow direction as well as temperature: a continuous stream of cool air across the bed can feel uncomfortable even when the room itself is not especially cold.
To make overnight cooling more comfortable:
- Direct airflow away from your face and body.
- Choose bedding suitable for the conditions.
- Use a timer if cooling is only needed for part of the night.
- Check what your model’s Sleep mode actually does.
Sleep modes vary. Some change the target temperature over time, while others also adjust fan speed or noise levels. Consult the operating manual rather than assuming every air conditioner works the same way.
Individual comfort and health needs should take priority over a general energy-saving temperature recommendation.
Does Setting Your Air Conditioner to 18°C Cool the Room Faster?
Choosing 18°C does not guarantee faster cooling. The number on the controller is the temperature you want the system to reach, rather than a direct setting for the temperature of the air leaving the vents.
Cooling speed depends on the system’s available capacity, its controls and how much heat is entering the room.
Inverter air conditioners can vary their output in response to operating conditions. A lower target may affect that response, but it cannot create unlimited cooling capacity. Once the room reaches a comfortable temperature, an unnecessarily low setting can keep it cooling further than you need.
If your unit has a Powerful or Turbo function, check the manufacturer’s instructions for its intended use. The same principle applies to heating: selecting a much higher target is not a reliable shortcut to warming the room.
Why Does the Same Temperature Feel Different in Different Rooms?
A thermostat setting cannot describe everything happening inside your home. Several factors influence comfort.
Sun exposure and insulation
A room with afternoon sun can gain heat quickly through windows and surrounding surfaces. Insulation and shading help limit that heat gain.
Air movement and humidity
Moving air can make you feel cooler without reducing the room temperature. Humidity also affects how warm or sticky a space feels. Daikin’s explanation of cooling and dry modes describes why temperature and humidity need to be considered separately.
Temperature sensor location
The system responds to the temperature measured by its sensor. Depending on the installation, that sensor may be in the indoor unit, a wall controller or an individual zone.
The temperature around that sensor may differ from the temperature where you are sitting.
System size and room layout
A unit designed for one room may struggle if it is expected to cool adjoining spaces as well. High ceilings, large windows and open layouts also affect the cooling required.
If sizing could be an issue, try Hurricane Air’s air conditioning size calculator for an initial estimate. A professional assessment can account for conditions that a simple calculation may miss.
Ducted zoning
Zoning can help direct conditioning towards occupied areas. However, the system still needs suitable airflow.
Follow the installer’s operating instructions rather than closing every unused vent or running fewer zones than the system permits. For suitable installations, smart air conditioning and zoning can provide more control over different areas of the home.
How to Stay Comfortable Without Turning the Temperature Down
Small changes around the home can reduce the work your air conditioner needs to do.
Shade windows before the room heats up
Close blinds or curtains on sun-exposed windows before direct sunlight warms the room. External shading can also help reduce heat entering through glass.
Use a fan where it helps
A ceiling or portable fan can improve comfort by moving air over your skin. You may find that a higher air conditioner setting feels comfortable when a fan is running.
Keep conditioned air inside
When using refrigerated split or ducted air conditioning, avoid leaving windows and external doors open unnecessarily.
Evaporative cooling operates differently and requires appropriate ventilation, so follow the instructions for your particular system.
Keep filters clean
Restricted airflow can reduce performance. Check accessible filters according to the manufacturer’s instructions and clean them when needed.
Our guide explains how to clean your split system filter without attempting deeper internal servicing.
Use timers around your routine
Schedule operation around when rooms are occupied. There is no universal rule that leaving an air conditioner running all day is cheaper than switching it off when it is not needed. The result depends on the building, weather, equipment and electricity tariff.
Address declining performance
If a previously comfortable setting no longer works well, the answer may be maintenance rather than a colder target. Air conditioner servicing in Perth can help identify airflow and performance issues.
What if Your Air Conditioner Cannot Reach the Set Temperature?
A room remaining warm does not automatically mean the thermostat setting is wrong.
Check the operating mode, accessible filters, open windows and obvious obstructions around the unit. Consider whether the system is being asked to cool additional rooms or cope with unusually high heat entering the space.
Persistent poor cooling can also involve a fault. Our guide to reasons your split system is not blowing cold air explains the possibilities in more detail.
Arrange professional assessment if poor performance continues, particularly if you notice unusual noises, recurring leaks or ice formation. Avoid opening electrical compartments or attempting refrigerant work yourself.
Frequently Asked Questions
Is 24°C a good air conditioner setting?
Yes. It sits within the recommended summer starting range. If you are equally comfortable at 25°C or 26°C, the higher setting reduces the amount of cooling you are asking the system to provide.
Is 26°C too warm for air conditioning?
Not necessarily. Many people find it comfortable, particularly with shading and good air movement. Adjust the setting if it does not meet your needs.
Should I use Cool, Auto or Dry mode?
Use Cool when you want to lower the room temperature. Dry focuses on moisture removal and may offer limited temperature control. Auto operating mode may select heating or cooling according to room conditions.
Auto fan speed is a separate function on many controllers. Check your manual, as available settings differ between models.
Do split and ducted systems need different temperatures?
The same starting ranges can apply to both refrigerated systems. The main differences are how air is distributed, where temperatures are measured and how much of the home is being conditioned.
Should I leave my air conditioner running overnight?
Use it for as long as needed to maintain suitable sleeping conditions. A timer may suit a room that stays comfortable after cooling, while other rooms need temperature control through the night.
Need Help From Perth’s Air Con Experts?
A suitable temperature setting should work alongside a correctly sized, well-maintained system.
If your air conditioner struggles to keep your home comfortable, Hurricane Air can assess its performance and recommend the next step. Our team provides air conditioner repairs in Perth for systems that need more than a change on the remote.
