What's the cheapest way to cool a room? Fans, portables and splits priced per hour (Australia)

The first hot week of the year is when the cooling decision gets made — usually at 9pm, in a stuffy bedroom, on the way to the shops for whatever’s in stock. So here’s the question answered before the heat arrives, with actual numbers: what does an hour of cool cost, appliance by appliance?

One honesty note before the table, because cooling isn’t one thing. Some of these machines lower the room’s temperature. Some only make you feel cooler. The table says which — and it turns out that distinction is where the money is.

The per-hour scoreboard

Priced at the guide’s working rate of 36c/kWh. (Market averages currently run about 30–35c/kWh depending on your state, so scale to your own rate — it shifts the cents, not the order.) Air-conditioner figures are at full power; more on that below.

Cooling	What an hour costs	What you actually get
Ceiling fan (DC motor ~30 W; older AC motor ~60 W)	~1–2c	Feels about 3°C cooler where the air moves. Doesn’t cool the room
Pedestal or tower fan (40–50 W)	~2c	Same — it cools people, not rooms
Portable evaporative cooler (~90–140 W, plus water)	~3–5c	Spot cooling in dry air only. Needs a window open. Does nothing useful in humidity
Split system, 2.5 kW (a bedroom)	~18c	Real cooling: 2.5 kW of it, about 5 units of cool per unit of electricity
Whole-house ducted evaporative (fan + pump)	~20c (10–50c, by fan size)	Cools the whole house — in dry climates, with the windows open, using 25+ litres of water an hour
Window/wall box unit, 2.7 kW	~30c	Real cooling, about a third less efficient than a split
Split system, 3.5 kW (a living room)	~30c	3.5 kW of cooling
Portable refrigerated air conditioner, 2.6 kW	~36c	Real cooling, but about half a split’s cool per unit of electricity — the one with no stars on its label
Split system, 7 kW (big open-plan)	~72c	7 kW of cooling
Ducted reverse-cycle, 14 kW (whole house, every zone open)	~$1.60	14 kW of cooling, before whatever leaks out of the ducts. Close zones and it drops

Three findings fall out of that table.

A fan costs one-tenth to one-twentieth of an air conditioner — and buys about 3°C of comfort. That’s the Australian Government’s own figure: moving air “provides a similar improvement to comfort as reducing the temperature by around 3 °C”. Since every degree you turn an air conditioner down adds roughly 10% to its running cost, three degrees of fan is worth about a quarter to a third of the air conditioner’s bill — for 2c an hour.

The portable air conditioner is the oil-column heater of summer. It feels like the cheap option — no installer, no landlord — and it’s the most expensive cool in the table per unit delivered. CHOICE’s finding is blunt: single-duct portables are “quite inefficient, giving you less cooling for your kilowatt”, and “can cost about twice as much to run as a split-system air conditioner of a similar size”. The reason is the hose: it blows hot air outside, which sucks warm air back in from the rest of the house through every gap. That’s why the energy label on a single-hose portable shows no stars at all — the only air conditioner sold here that way.

If you own a split, you already own the cheapest real cooling in the house. A modern 2.5 kW inverter split delivers about five units of cooling for every unit of electricity. Nothing else on the list comes close — and the per-hour figure above is its ceiling: once the room reaches temperature, an inverter throttles right back. CHOICE puts it plainly — they “can maintain a comfortable indoor temperature while running at very low power”.

Four things that change the numbers

• The thermostat. Set cooling to 25°C or higher — the federal guidance says 25–27°C, the state energy departments 24–26°C — because every degree lower adds about 10% to the running cost. Twenty-one degrees isn’t a temperature, it’s a surcharge.
• The fan-plus-aircon combination. Run the air conditioner a few degrees warmer with a fan moving the air, and you get the same comfort for roughly a quarter to a third less. This isn’t a hack, it’s the official advice: YourHome says the saving from the air conditioner’s shorter running “more than offsets the cost of fan use”, and NSW’s energy department puts fans with occasional air conditioning at up to 76% less energy than air conditioning alone. The single best cooling trick in the country, and it costs 2c an hour. (One catch from CSIRO: fans cool people, not rooms — switch them off when you leave.)
• Full power versus real power. The air-conditioner figures are what the machine draws flat out on a 35°C afternoon. Pull the blinds, close the doors and set 25°C, and a good inverter spends most of the evening idling well below that. A portable can’t do this trick — it’s mostly on or off.
• Evaporative runs the opposite way. A refrigerated air conditioner wants the house closed. An evaporative cooler wants windows open — it pushes damp air through the house and out. Run one with everything shut and you get a humid room and nothing else. And it only works in dry air: the government’s design guidance reserves evaporative cooling for the hot, dry inland — Mildura, Broken Hill, Tamworth. Canberra’s dry summer is “reasonably effective” territory by the ACT’s own guidance; Melbourne’s afternoons run 40–50% humidity, so it’s borderline; and the humid coast — Brisbane, Darwin, Sydney on a sticky day — is the wrong climate for it altogether.

”Should I go buy a split, then?”

Here’s the honest version, because the answer depends on where you’re starting from:

• Cooling one bedroom with a portable air conditioner most summer nights? On the cooling saving alone, no — a split costs about $1,800–2,800 installed, and the running-cost gap over a summer is roughly $65–110. That’s decades of payback. But the split’s case was never a summer case. The same unit replacing a bar or oil-column heater in winter saves around $500 a year and pays for itself in about 3–6 years — we priced that here. Buy it for winter. Summer comes free.
• Already own a portable? Keep using it, but use it well: seal the window kit properly, run it before the room gets hot rather than fighting a heat-soaked room at 9pm, put a fan in the room with it, and set it warmer than you think. It’s a bedroom device — don’t ask it to cool a living area.
• Renting? Fans first, always. Then a portable or a box unit if the lease allows one — and the fan-plus-aircon combination matters even more for you, because it’s the one lever that doesn’t need permission.
• Already own a split and running it at 21°C with the fan off? Turn the fan on and the dial up tonight. That’s the cheapest cooling decision in Australia — it costs nothing.

The other half: stop the heat getting in

Everything above is about the cost of making cool. The other half of the bill is how fast the heat gets in — and three fixes beat every appliance in this article on value:

• Shade the glass, from outside. The government’s YourHome guide puts it starkly: up to 87% of a home’s summer heat gain comes through the windows, and effective shading blocks up to 90% of it. Order matters, though — an external blind, awning or even a sheet pegged over a west-facing window stops the heat before the glass; internal blinds and curtains catch it after it’s already inside, which YourHome calls “much less effective”. Closing them still helps. Shading outside helps far more.
• Run the house like an esky. Shut up in the morning — windows, blinds, doors to rooms you’re not using — and open up in the evening once it’s cooler outside than in. YourHome’s rule: cross-breeze “when the temperature outside is better than inside. Keep them closed when outside is hotter.” It works best inland, where nights drop properly; it doesn’t work with the air conditioner running (you’re pumping out air you paid to cool), or on smoky, noisy or insecure nights.
• Insulation and draughts work in both directions. The ceiling insulation and door seals that cut your heating bill cut your cooling bill the same way — a leaky house lets the hot air in as readily as it let the warm air out. And they’re the reason pre-cooling works at all: only a well-sealed, insulated house holds its cool long enough to be worth making early. Draught-proofing is priced here.

Two smaller ones: clean the air conditioner’s filter and keep it serviced (the federal energy department’s bench tests found neglected units — blocked coils, low refrigerant — running 14–20% behind), and give the outdoor unit shade and clear airflow — YourHome says it “should be shaded from direct sun”. And don’t leave it running overnight or while you’re out; the government’s advice is the same as your parents’.

The bigger picture

Cooling is the biggest summer lever, but only one. If your air conditioner is ducted, here’s what it costs to run over a season; if you’re sizing a new one, here’s how to tell if the quote is oversized. And if you’re on a time-of-use plan, when you cool matters as much as how: the evening peak — roughly 3 or 4pm to 9pm in most states — is exactly when the air conditioner works hardest. Every network’s peak and off-peak times are here; if your house is well insulated, the cheap midday window is when to get it cold and then shut the door on the peak.

If you want every lever priced the way this article prices coolers — savings, cost, payback, including the upgrades that aren’t worth it — that’s the guide. And to see whether cooling is even your problem, check your bill against homes like yours first.

Figures: 36c/kWh is the sourced working rate from the Decode Energy Home Energy Saving Guide (AU 2026 edition); market averages sit at roughly 30–35c/kWh by state, so our table runs a touch generous. Appliance power draws are rated figures from registered models (splits: Daikin, Mitsubishi Electric and Fujitsu 2.5–7.1 kW classes; portable and box units: TECO, De’Longhi, Rinnai, Kelvinator; ducted: Daikin and Mitsubishi Electric 14 kW) and Australian Government guidance (YourHome 2026 for fans and evaporative). The 3°C fan effect, the thermostat ranges, the evaporative climate guidance, the 87% window figure and the 14–20% maintenance finding are the Australian Government’s (YourHome, energy.gov.au, Sustainability Victoria, NSW and ACT energy departments); the per-degree rule is “about 10%” in the state guidance and “5 to 10 per cent” in YourHome; the portable air-conditioner findings are CHOICE’s. The fan-plus-aircon saving and the portable-versus-split payback are our arithmetic from those sourced figures. Your rates and climate shift the exact cents; they don’t change the order of the table.