Best Temperature Setting for an Air Conditioner

Cooling mode — what to set

For cooling in summer, most people find 22–24°C comfortable. Setting the thermostat at 20°C or below does not cool the room faster — the aircon always works at maximum cooling until it reaches the target. A very low setpoint simply means the unit runs longer and uses more electricity.

Each degree you lower the setpoint in cooling mode increases energy use. If 24°C is comfortable, there is no benefit in setting 20°C.

At night, sleeping comfort varies by individual, but a slightly higher setpoint — 24–26°C — often works well combined with a fan mode or the sleep timer function.

Heating mode — what to set

In heating mode, 20–22°C is a reasonable range for a living area or office. Higher than that increases running cost without proportionate comfort benefit.

Heat pump air conditioners are highly efficient in heating mode — they move heat rather than generate it — but efficiency drops significantly as outdoor temperatures fall below about 5°C. At very low outdoor temperatures, supplementary heating may be needed.

Auto mode and humidity

Many units offer an auto mode that switches between cooling and heating to maintain the setpoint. This works well in climates with variable temperatures throughout the day. Auto mode is not the same as the fan-only mode (which does not run the compressor).

High humidity makes a room feel warmer than the thermometer reads. Running the unit in dry mode or at a slightly lower temperature setpoint can improve comfort without lowering the temperature significantly.

Energy saving tips

• ✓ Set 24°C in cooling mode where comfortable — each degree lower adds to running cost
• ✓ Use a timer to start cooling shortly before you need the room rather than leaving it on all day
• ✓ Keep doors and windows closed when the unit is running
• ✓ Close blinds on west- and north-facing windows in the afternoon to reduce heat load
• ✓ Clean the filter monthly — a blocked filter forces the unit to work harder

Protecting the unit

Running an air conditioner at extreme setpoints — 16°C in a hot room, or back and forth between heating and cooling — does not damage it, but does increase wear. Consistent use within a normal comfort range is easiest on the system.