How we work it out
An air conditioner doesn't gobble the power its cooling number suggests. A "5 kW aircon" delivers 5 kW of cooling while drawing about 1.4 kW of electricity, because a heat pump moves heat around rather than making cold from scratch. You get three or four units of cooling for every unit of power. The draw figures behind the size picker are medians of nearly 4,100 currently registered units in the energyrating.gov.au database, July 2026 snapshot. That efficiency ratio is why running the aircon usually costs less than people expect, and why a $30 fan heater can out-cost a $1,200 split system.
Worked example: a 5 kW split system in NSW drawing the registry median of 1.35 kW: 1.35 × 32.4¢ = about 44¢ an hour. Six hours on a scorcher is $2.62, call it $79 for a properly hot month. The one to watch is whole-home ducted. At around 3.93 kW of draw it costs more like $1.27 an hour, so zoning off empty rooms pays real money. Pick "Portable" or "Window / wall unit" above at any of the three sizes and the docket also works out how many months it takes a same-size split system's running-cost saving to pay back the extra unit-and-install cost.
Cutting the cost without sweating through January
Every degree colder adds roughly 10% to the running cost, and 24°C is the sweet spot for summer. Clean the filters each season, since a clogged filter can add another 10%. Shut the curtains on the western sun before the heat gets in. If you've got solar, the cheapest cooling of your life happens between 10am and 3pm, so pre-cool the house while the panels are paying for it.
Common questions
Does heating cost the same as cooling?
Near enough. Reverse-cycle heating uses the same heat pump efficiency, which makes it the cheapest form of electric heating in Australia. It delivers the same warmth for about a third of the cost of a plug-in heater.
Is it cheaper to leave the aircon on all day?
For houses, no. The unit works hardest, and costs most, holding a set temperature against peak heat. Cooling the place down when you get home, or pre-cooling on solar, beats running it for hours in an empty house.
What about a portable air conditioner?
Portables are the battlers of the aircon world. Matched against a split system rated for the same cooling output, the energyrating.gov.au registry shows portables drawing 67% more power for the identical job. Fine for a rental, dear to run long term. See our portable vs split system running cost breakdown for the full state-by-state numbers.
What about a window or wall unit?
A window/wall unit is the sleeve-style box you see built into a single wall or window, common in older apartments and units that were never plumbed for a split system's outdoor unit. It sits between the other two on running cost: the energyrating.gov.au registry's 228 currently registered window/wall models draw a median of 0.82–1.6 kW across the small-to-lounge-room sizes, more than an equivalent split but less than a portable of the same cooling output, since it still exhausts heat straight outside rather than through a hose vented into the room it's cooling. Pick "Window / wall unit" above to price yours.
Is it worth installing a split system to replace a portable or window unit?
Only if you're staying put for a few years. Across the three sizes the docket compares, a cheap portable or window/wall unit currently costs $424–$1299 depending on size and type, and a same-size split system runs $1200–$2800 supplied and installed. A bigger split costs more to buy and install, not just more to run. The running-cost saving typically earns that gap back within a few years of regular use; a renter running it for one summer won't recover the install cost, but someone in the place long-term usually will. Pick your own size and unit type above for an exact months-to-payback figure.
What this costs, state by state
A 5 kW split system at the registry-median 1.35 kW draw, run 6 hours a day.
| State | Rate | Per day | Across summer |
|---|---|---|---|
| New South Wales | 32.4¢ | $2.62 | $236 |
| Victoria | 29.8¢ | $2.41 | $217 |
| Queensland | 31.2¢ | $2.53 | $227 |
| South Australia | 38.1¢ | $3.09 | $278 |
| Western Australia | 33.6¢ | $2.72 | $245 |
| Tasmania | 28.9¢ | $2.34 | $211 |
| Australian Capital Territory | 27.4¢ | $2.22 | $200 |
| Northern Territory | 31.7¢ | $2.57 | $231 |
Reference rates for 2026–27. Your row is highlighted once you set your location.
Sources
Electricity rates: AER Default Market Offer (NSW, SA, south-east QLD), Victorian Default Offer, and each remaining state's regulated tariff, current for 2026–27. Appliance figures: the energyrating.gov.au registration database (July 2026 snapshot). Methods and assumptions are described on each page.