How much does it cost to run an air conditioner?

Capacity is not power use

The size of an air conditioner, like “7 kW”, is its capacity: the heat it moves in or out of the room. The electricity it draws is the rated input, and it is much lower. The median 7.1 kW split on the Energy Rating registry has a rated cooling input of 2.00 kW. A 2.5 kW split draws about 0.55 kW.

That is why “7 kW × your rate” is the wrong cost for a 7 kW aircon. It prices the heat moved, not the power drawn. At the real input of about 2 kW, the same unit costs less than a third of that an hour flat out, and much less on a typical hour.

The label kWh for your zone

The Zoned Energy Rating Label splits Australia into three climate zones. Each zone shows a blue cooling kWh and a red heating kWh a year.

• Hot (modelled on Rockhampton): Brisbane, Darwin.
• Average (modelled on Richmond, northwest of Sydney): Adelaide, Perth, Sydney.
• Cold (modelled on Canberra): Canberra, Hobart, Melbourne.

The official way to estimate a year’s cost is to add the cooling and heating kWh for your zone and multiply by your rate. The label is best used to compare models: a unit with a 20% higher kWh figure will use about 20% more electricity. If you only run it on the hottest or coldest days, you will likely use less than the label says.

The zone mix matters a lot. In the Hot zone, cooling uses about 9 to 12 times the kWh of heating. In the Cold zone it is the other way round: heating uses about 7 to 9 times the kWh of cooling.

Inverters at part load

Most air conditioners sold in Australia are inverters. They run flat out while pulling the room to temperature, then slow down. On the registry’s half-capacity test, a median unit at 50% capacity draws only about 37% of its rated input, and it is about 1.35 times as efficient.

The “Per hour, flat out” figure on this page is the cost of an hour at the rated input. A typical hour costs far less. Our “typical hour” uses an estimated average load, shown under “How we calculated this”. Treat it as an estimate, not a measurement.

Watch out for

• Single-duct portable air conditioners get 0 stars. The regulator says they have no overall cooling effect on the room.
• Old labels and new labels are not comparable. Old-label stars cannot be converted to new-label stars.
• Time-of-use rates. This calculator uses one flat rate. On a time-of-use plan, evening use hits peak rates, so your real cost can be higher. Solar you use yourself will make it lower.

Reverse cycle heating vs a plug-in heater

Reverse cycle air conditioners move heat instead of making it, so they use far less power than a plug-in heater for the same warmth. To compare the two, use the heater running cost calculator.

What a 2.5 kW split costs to run

A 2.5 kW split in the Average zone uses about 538 kWh a year on its label: about $172 a year at 32c/kWh. Flat out it costs about $0.18 an hour to cool. The table of every size in "How we calculated this" uses your own settings.

• The median 2.5 kW split draws 0.55 kW at full cooling. Its EER is 4.63, against 3.54 for the median 7.1 kW split, so small units move more heat for each kWh. (Energy Rating registry ac_2026_09_17.csv, deduplicated medians)
• In the Average zone a typical 7.1 kW split uses about 3.5 times the cooling kWh of a 2.5 kW (594 against 170 a year). (Energy Rating registry ac_2026_09_17.csv, deduplicated medians)
• The government does not endorse a sizing tool. Room size, windows and their direction, insulation and shading all matter. A licensed installer can advise. (GEMS Regulator, questions and answers on the zoned label, Q7; Not yet checked)