What actually costs the money
A reverse-cycle unit's job is closing the gap between the air outside and your setpoint inside, and it keeps spending power for as long as that gap exists. Holding 24°C against a 34°C afternoon in an empty lounge room draws the same power as holding it against a 34°C afternoon with people sitting in it. There's no efficiency reward for cooling a room nobody's in, which is the whole case for switching off: energy.gov.au's own seasonal advice is to turn the aircon off when you leave the house, and that each extra degree of cooling adds roughly 5-10% to the running cost.
What this costs, state by state
Same 5 kW split system as our calculator (1.35 kW registry-median draw): a normal after-work stint against leaving it on non-stop.
| State | Rate | 6 hrs/day | 24 hrs/day |
|---|---|---|---|
| New South Wales | 32.4¢ | $2.66 | $10.65 |
| Victoria | 29.8¢ | $2.45 | $9.80 |
| Queensland | 31.2¢ | $2.56 | $10.26 |
| South Australia | 38.1¢ | $3.13 | $12.53 |
| Western Australia | 33.6¢ | $2.76 | $11.05 |
| Tasmania | 28.9¢ | $2.38 | $9.50 |
| Australian Capital Territory | 27.4¢ | $2.25 | $9.01 |
| Northern Territory | 31.7¢ | $2.61 | $10.42 |
Reference rates for 2026–27. Your row is highlighted once you set your location.
When leaving it running does pay off
The blanket answer is turn it off. There are exceptions: a person, baby or pet is home all day in genuinely dangerous heat, where the aircon's job is safety, not economy. You've got rooftop solar and you're home during the day, so pre-cooling or holding a setpoint between roughly 10am and 3pm uses power that's already close to free (see our aircon running cost calculator for your own system's numbers). Or you're managing humidity in a mould-prone home, where a steady setpoint is doing a different job than temperature alone.
None of this is about compressor restarts. A modern inverter split doesn't punish you for switching off, despite the myth going round. See the FAQ below.
Common questions
Does turning the aircon off and on again use more power than leaving it running?
No, not in any way that matters for a modern inverter split system. Older single-speed units draw a brief surge on restart, but it lasts seconds and comes nowhere near offsetting hours of not running at all.
What temperature setting is cheapest to run?
24°C for cooling. Each degree colder adds roughly 5-10% to the running cost, per energy.gov.au's seasonal advice, which is why 24°C is the number most manufacturers and regulators land on.
Does a portable air conditioner cost more to leave running than a split system?
Yes, meaningfully more, since a portable already draws about two-thirds more power than a split doing the same cooling job. See our companion guide on portable vs split system running costs for the full comparison.
Sources
Electricity rates: AER Default Market Offer and each state's regulated reference tariff, current for 2026–27. Appliance draw: the energyrating.gov.au registration database (July 2026 snapshot). Cooling behaviour and setpoint advice: energy.gov.au, Summer energy savings.