Switch a domestic split off when the house is empty, unless a person will be back the same day and you have a clear reason. Cooling an unoccupied room spends electricity and hides a condensate problem until you see the ceiling. A pump makes that worse, because the alarm is only useful if someone hears it. A modest setpoint is the alternative when a sitter has asked you to hold the rooms. 16C is not that alternative. Windows should stay closed if it runs, and a neighbour should know where the isolator is.
Nobody is in the chair
The comfort problem disappears when nobody is in the chair. Furniture does not need 22C. A heatwave will warm the fabric of the house, and a split switched on an hour before you get home will pull it back faster than a unit that has been grinding all week at the bottom of the scale.
If you run it anyway, shut the internal doors of the rooms that have indoor units so you are not chilling the whole stair. Keep windows closed. A cracked sash in an empty house is a running cost with the security risk of an open window. Night purging by opening windows only makes sense with the unit off and the house secured in a way you accept.
Condensate with the house shut up
Condensate is continuous in humid weather. A slipped hose or a failed pump puts water on a floor or into a ceiling with no one to move a bucket. That is the main reason an empty fortnight and a running split are a poor pair. Gravity to a proper waste is calmer than a pump, and it can still block. If a pump is unavoidable, ask where the alarm can be heard and what the unit does when the float lifts, and ask for the isolator to be labelled.
When you return, look at the drain end and the indoor tray area before you congratulate yourself. Musty smell and a tide mark are the clues. The first service, often at the end of the cooling season, is when an installer should see that drain. A flood in week two of a holiday is a call-back, not a service. The outdoor unit should still be free of leaves when you leave, so it is not labouring into a blocked coil. Planning Portal rules and F-gas paperwork do not change because you are at the airport.
Frequently asked questions
Should I leave the air conditioning on to stop the house getting hot?
For an empty house, off is usually right. Switch it on when people return. Continuous cooling mainly adds cost and a leak you will not see.
Is a low setpoint safer while we are out?
No. 16C runs the unit harder and can ice the coil and overflow the drain. If someone insists on leaving it on, use a modest setpoint and a person who will check.
Can a neighbour switch it off if there is a storm?
Yes, if you have shown them the isolator and asked them to use it when the casing is damaged. Ask them not to hose the outdoor unit.
Does a holiday icon change the empty-house decision?
Even if an icon exists, the decision is about water, cost and whether anyone will look. A timer or a mild setpoint shift is not a caretaker.
What if a sitter or a pet is in the house?
A house sitter or a pet visit is a person. Agree a setpoint they can understand, and show them fan speed so they do not chase comfort with a colder number. The unit's kilowatts are fixed. Lower on the remote mostly means longer running. Do not leave cooling as a substitute for someone checking bowls and windows.
Should every indoor unit run while we are away?
Default to off if nobody is home. If you do leave one running, shut that room's doors and windows. Do not use 16C as background cooling, and tell a neighbour where the isolator is if a pump is fitted.
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How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.