Heating and cooling running costs
Heating and cooling is about 40% of household energy on the Australian Government's figures — usually the biggest single item on the bill, and the one where the received wisdom is most often wrong.
The thing almost nobody expects: everywhere south of Brisbane, heating costs several times what cooling costs. People worry about the air conditioner in February. The money leaves in July.
Heating against cooling, city by city
The same 160 m² house with the same multi-split system, moved around the country, at each state's own electricity price. The last column is the ratio between the two.
| City | Heating / cooling degree days | Heating a year | Cooling a year | Which dominates |
|---|---|---|---|---|
| Hobart, TAS | 1,813 / 0 | $1,184 | $0 | heating only — no cooling season |
| Canberra, ACT | 1,833 / 210 | $1,581 | $144 | heating costs 11.0× |
| Melbourne, VIC | 1,239 / 173 | $795 | $92 | heating costs 8.7× |
| Adelaide, SA | 793 / 563 | $775 | $359 | heating costs 2.2× |
| Sydney, NSW | 478 / 683 | $369 | $331 | heating costs 1.1× |
| Perth, WA | 545 / 872 | $423 | $405 | heating costs 1.0× |
| Brisbane, QLD | 193 / 1,208 | $126 | $442 | cooling costs 3.5× |
| Darwin, NT | 0 / 3,508 | $0 | $1,175 | cooling only — no heating season |
A 160 m² house built before 2005, with one multi-split system, at each state's own electricity price. The same hardware, the same house, moved around the country. Heating outweighs cooling everywhere south of Brisbane, and in Melbourne and Canberra it is not close — while Sydney and Perth are near enough level. It is the air conditioner people worry about in February.
Melbourne is the extreme case at nearly nine to one, but even Sydney and Perth spend more on heating than cooling. Only Brisbane and Darwin flip it. If you are trying to cut a power bill in the southern half of Australia, the winter half of the year is where the money is.
The systems
| System | Does | Conditions | Typical life | Installed cost |
|---|---|---|---|---|
| Single split system | Heating and cooling | One main living area | 12 years | $2,600 |
| Multi-split system | Heating and cooling | Most of the house | 12 years | $8,500 |
| Ducted reverse cycle | Heating and cooling | The whole house | 15 years | $15,500 |
| Ducted gas heating | Heating only | The whole house | 15 years | $10,250 |
| Gas space heater | Heating only | One main living area | 15 years | $2,700 |
| Electric panel or fan heater | Heating only | One room | 8 years | $225 |
| Ducted evaporative cooling | Cooling only | The whole house | 12 years | $6,500 |
| Ceiling fans | Cooling only | The whole house | 15 years | $600 |
Installed cost is the midpoint of a supply-and-fit range before any rebate, and it is a market observation rather than a published figure — treat it as a starting point for quotes, not as a price. Read the “conditions” column alongside the running costs: the cheapest systems to run are the ones that heat or cool the least of your house, which is a real saving but not the same as efficiency.
Read the "conditions" column first
This is the part that makes most comparisons misleading. A single split system has the lowest running cost of anything in the table — because it heats one room. A ducted system has the highest — because it heats the whole house. Those are different products doing different jobs, and putting their annual costs side by side without saying so implies a difference in efficiency that is mostly a difference in scope.
Our calculator shows the conditions column next to every figure for exactly that reason. A multi-split really is cheaper than ducted, and part of the reason really is that it lets you heat the room you are sitting in rather than the hallway.
What it costs in each state
| State or territory | Ducted reverse cycle | Multi-split | Ducted gas + split for cooling |
|---|---|---|---|
| New South Wales | $1,188 | $820 | $1,207 |
| Victoria | $1,450 | $1,006 | $2,006 |
| Queensland | $1,002 | $688 | $831 |
| South Australia | $1,800 | $1,254 | $1,795 |
| Western Australia | $1,369 | $949 | $1,934 |
| Tasmania | $1,870 | $1,304 | no mains gas |
| Australian Capital Territory | $2,635 | $1,846 | $2,927 |
| Northern Territory | $1,858 | $1,295 | no mains gas |
A 160 m² pre-2005 house, heated and cooled for a full year, at each state's reference rates, including annual servicing. Cheapest in each row is in bold. Ducted gas only heats, so that column includes a single split system to cool with — otherwise it would be buying half of what the reverse cycle columns buy and the comparison would flatter it. Hobart needs no cooling and Darwin no heating, so the pairing is dropped where there is nothing for it to do. Note also that ducted and multi-split do not condition the same amount of house — see the conditions column in the calculator.
These are running costs only. What a new system costs to put in also depends on where you live: there is no federal rebate for heating or cooling, so the discount runs from nothing at all in three states and territories to several thousand dollars in Victoria. Heating and cooling rebates by state has what each scheme pays and who qualifies.
The thing that beats every system: the building
No appliance on the market saves as much as insulation, draught sealing and decent glazing. The same house and the same ducted system, built to four different standards:
| House | Heating energy | Cooling energy | Heating a year | Cooling a year | Total |
|---|---|---|---|---|---|
| Built before 2005, or no insulation upgrade | 100% | 100% | $521 | $468 | $988 |
| 5 star — built roughly 2006 to 2011 | 40% | 75% | $208 | $351 | $559 |
| 6 star — built 2012 or later | 30% | 60% | $156 | $281 | $437 |
| 7 star — built to the 2023 code, or deeply retrofitted | 22% | 50% | $115 | $234 | $348 |
The same 160 m² house and the same ducted reverse cycle system in New South Wales, built to four different standards. Insulation cuts heating energy to under a third and cooling energy only to about 60% — they are not the same problem, and a single “efficiency” figure for both is wrong about one of them. No system on the market saves as much as the building fabric does.
Note that insulation is far more effective against heating than cooling — a 6-star house needs 30% of the heating energy of a pre-2005 one but 60% of the cooling energy. They are not the same problem. Heat leaks out through the fabric all winter; heat comes in through windows and roofs in summer, which is why shading and window treatment matter more for cooling than bulk insulation does.
Guides
Split, multi-split or ducted?
The comparison that is usually presented as an efficiency question and is mostly a scope question. What each one actually costs, and when the expensive one is the right answer anyway.
Ducted gas versus reverse cycle
The most consequential heating decision in southern Australia, and one where the answer has changed. What the numbers say now, and what the 86% on the gas compliance plate does not tell you.
Heat pump hot water
A reverse cycle air conditioner and a heat pump water heater are the same technology pointed at different problems — and the nameplate figure overstates both.
Frequently asked questions
What does it cost to run an air conditioner for an hour?
For a typical 3.5 kW split system drawing about 0.9 kW while running, roughly 30 cents an hour at a standard rate — but that number is close to useless on its own, because an inverter unit does not draw its rated power continuously. It works hard to bring a room to temperature and then throttles back to a fraction of that. What matters is the annual figure, which is what the calculator produces.
Is it cheaper to leave the air conditioner on all day?
No. This myth comes from the fact that inverter units are inefficient at start-up and efficient when cruising, which is true, but it does not outweigh the hours of running you avoid by switching off. A house left conditioned all day is losing heat to the outside all day and paying to replace it. Turn it off when you leave; the start-up penalty is minutes, not hours.
Does every degree on the thermostat really matter?
Yes, and more than most advice suggests. Each degree changes the temperature difference the system is working against, which is what drives the energy use — roughly 5 to 10% per degree in most Australian climates. Setting heating to 20 °C rather than 23 °C is one of the few free changes on this site that genuinely shows up on a bill.
Is evaporative cooling worth it?
In a dry climate, yes — it runs at roughly a quarter of the cost of refrigerated cooling because it is a fan and a water pump rather than a refrigeration circuit. In a humid one it barely works, because it cools by evaporating water into air that is already close to saturated. Perth, Adelaide and inland Victoria are good candidates. Brisbane, Sydney's coast and anywhere in the tropics are not.
Do ceiling fans actually save anything?
They do not cool air, they move it, and moving air makes skin feel about three degrees cooler. That means the saving is indirect: a fan lets you set the air conditioner two or three degrees higher for the same comfort, and at 5 to 10% per degree that is a real reduction. A fan running in an empty room saves nothing at all, because there is no skin for it to cool.