9 min read
What is a split system air conditioner?
Short answer
A split system air conditioner has an indoor unit on the wall and an outdoor unit with the compressor, joined by refrigerant pipes, and moves heat out of the room in summer and, if it is reverse cycle, into it in winter. Almost every split sold in Australia in 2026 is an inverter reverse cycle model, and one costs about $1,500 to $4,800 installed on a standard install.
Prices are estimates, not quotes (how we estimate them). Rebate rules checked September 2026.
Compare 3 quotes for my houseA split system is called a split because the air conditioner is split in two. The noisy part lives outside. The quiet part lives on your wall. Two copper pipes and a cable run through the wall between them.
It is the most common air conditioner in Australian homes for good reasons. It is the cheapest fixed system to buy, the cheapest to run per room, and a good installer can have one working in a day.
Most people who ask what a split system is are really asking something else. Will it heat? How big? What does it cost to run? This page answers those in order.
How does a split system work?
A split system is a heat pump. It does not make cold. It moves heat from one place to another using a refrigerant that boils and condenses at useful temperatures.
In cooling mode the indoor coil runs cold. The fan in the indoor unit blows room air across it, the refrigerant inside the coil absorbs the heat and boils, and the cooled air comes back out into the room. The refrigerant gas travels out through the pipe to the outdoor unit. The compressor squeezes it, which makes it hot, and the outdoor fan blows that heat away across the outdoor coil. The refrigerant condenses back to liquid and returns inside to do it again.
Because it moves heat rather than generating it, a split is very efficient. The federal energy.gov.au guidance says a modern air conditioner turns one unit of electricity into three to six units of heating or cooling. A bar heater manages one.
As a side effect, the cold indoor coil pulls water out of the air. That is why a split has a drain pipe, and why a split feels better than a fan on a sticky Brisbane night.
The parts of a split system
| Part | Where it lives | What it does |
|---|---|---|
| Indoor unit (head) | High on an inside wall, or low on the floor for floor consoles | Holds the evaporator coil, fan, filters and louvres; blows conditioned air into the room |
| Outdoor unit | Outside wall, ground pad, bracket or roof | Holds the compressor, outdoor coil and fan; dumps heat outside in summer, collects it in winter |
| Refrigerant pipes | Through the wall, in a cover or cavity | Two insulated copper lines carrying refrigerant between the units |
| Interconnecting cable | Alongside the pipes | Power and control signals between the units |
| Condensate drain | Alongside the pipes, to a garden bed or drain | Carries away the water pulled out of the air |
| Remote or app | In your hand | Sets mode, temperature, fan, timer and quiet settings |
The indoor unit can sit a fair way from the outdoor unit. The government's YourHome guide puts it at up to 15 metres of separation. Every extra metre of pipe costs money and a little efficiency, so shorter is better.
What is a back-to-back install?
A back-to-back install puts the outdoor unit directly behind the indoor unit on the other side of the same wall. The pipes go straight through a hole in the wall and out the back. It is the shortest pipe run, the fastest job and the cheapest install.
It is also what most "standard installation" prices assume. If the head needs to go on an internal wall, upstairs, or anywhere the outdoor unit cannot sit directly behind it, the pipe run gets longer and the price goes up. The split system cost guide shows what those extras usually cost, and a local quote tells you whether your wall is back-to-back or not.
What is an inverter air conditioner?
An inverter air conditioner varies the speed of its compressor. An old fixed-speed unit runs flat out until the room hits the set temperature, switches off, lets the room drift, then switches on again. An inverter slows down as the room gets close and ticks over gently to hold the temperature.
That is quieter, holds the temperature more evenly, and uses less power. The YourHome guide says systems using inverter technology can save 40 per cent or more over standard units, and calls inverter splits the most efficient domestic air conditioners available.
In practice you do not have to go looking for one. Nearly every split sold by the major brands in Australia is an inverter. If a quote is for a non-inverter unit, it is either very old stock or very cheap stock. Ask which.
| Inverter | Non-inverter (fixed speed) | |
|---|---|---|
| Compressor | Varies its speed | On at full speed, or off |
| Temperature | Holds steady | Swings a degree or two either side |
| Noise | Quiet once the room is at temperature | Cycles on and off |
| Running cost | Lower; YourHome cites savings of 40% or more | Higher |
| Availability in 2026 | Almost every model from major brands | Rare; budget or old stock |
Split system vs reverse cycle: are they different?
No. They describe different things. "Split system" describes the layout: indoor unit, outdoor unit, pipes between. "Reverse cycle" describes what it can do: cool, and also heat by running the refrigerant loop backwards.
Almost every split system sold in Australia is reverse cycle. A cooling-only split exists, and you should not buy one unless you live somewhere that never gets cold. Heating is where a split earns its keep in Melbourne, Canberra, Hobart and most of the country for half the year. The full explanation is in what is reverse cycle air conditioning.
What sizes do split systems come in?
Splits are sold by capacity in kilowatts. That is the heat the unit can move, not the power it draws. A 7.1 kW unit uses roughly 1.8 kW of electricity at full output, and much less once the room is at temperature.
A rough guide is 100 to 140 watts of cooling per square metre for a typical insulated room. West-facing glass, a high ceiling or no insulation push you up a size. For a proper answer, use the size calculator, then get up to three local quotes so an installer can check the room for the things a calculator cannot see.
| Capacity | Room size (approx.) | Typical use | Installed price |
|---|---|---|---|
| 2.5 kW | 18 to 25 m² | Small bedroom, study | $1,500 to $2,500 |
| 3.5 kW | 25 to 35 m² | Main bedroom, small lounge | $1,700 to $2,700 |
| 5.0 kW | 35 to 50 m² | Lounge, family room | $2,100 to $3,300 |
| 7.1 kW | 50 to 70 m² | Open-plan living and kitchen | $2,600 to $3,900 |
| 8 to 9 kW | 60 to 90 m² | Large open-plan, raked ceilings | $3,000 to $4,800 |
Split system vs multi-split and ducted
A single split does one room or one open area. A multi-split runs two to five indoor heads from one larger outdoor unit, for $4,500 to $12,000 installed. Ducted hides a single fan coil in the roof and feeds every room through ceiling vents, for $7,500 to $18,000 in a typical house.
If one room does the living, a single split is almost always the right answer. The trade-offs are laid out in split vs ducted, and multi-split pricing is in the multi-split cost guide. Not sure which fits? Get up to three local quotes and say so; the installers will price the options that suit your house.
What to look for when buying a split system
- Reverse cycle, with the heating capacity stated, not just cooling.
- The right size for the room, not the biggest the installer has in the van.
- Star ratings on the Zoned Energy Rating Label for your climate zone. The label rates heating and cooling separately for hot, average and cold zones, and shows noise levels.
- Indoor noise at the lowest fan speed, if it is going in a bedroom. The quiet bedroom guide covers this.
- R32 refrigerant, which YourHome notes most new splits now use for its lower global warming potential.
- A brand with a service network near you. Our best split systems page and brand guides go through the options.
- An installer with an ARCtick licence. Here is what that means. Every installer we introduce when you get up to three local quotes holds one.
Want a number for your house? Check the rebate on your postcode. No name required. Check the rebate on your postcode.
Or do the sums yourself first: what size you need and what it costs to run.
Sources
FAQ
Common questions
What is a split system air conditioner?
It is an air conditioner split into two units: an indoor unit on the wall that blows conditioned air into the room, and an outdoor unit with the compressor. Refrigerant pipes connect them and carry heat out of the house in summer and, on a reverse cycle model, into it in winter.
How does a split system work?
Refrigerant absorbs heat from the room at the indoor coil, travels to the outdoor unit, is compressed, and releases that heat outside. In heating mode the flow reverses and heat is collected from outside air and released indoors. The unit moves heat rather than making it, which is why it is so efficient.
Is a split system the same as reverse cycle?
Not quite. Split system describes the two-unit layout; reverse cycle means it heats as well as cools. Almost every split sold in Australia is reverse cycle, so in everyday use the terms overlap.
What is an inverter air conditioner?
An inverter varies its compressor speed instead of switching fully on and off. It holds the temperature more evenly, runs more quietly and uses less power. The Australian Government's YourHome guide says inverter systems can save 40 per cent or more over standard units.
Do split systems use a lot of electricity?
Not much, for what they do. A modern 3.5 kW inverter split costs roughly 15c to 25c an hour once the room is at temperature, at about 32c/kWh. A 7.1 kW living-room unit is more like 35c to 50c. Use the running cost calculator for your tariff.
Is it better to leave an inverter air conditioner on all day?
Only if someone is home. Leaving it running in an empty house costs more than letting it restart, because an inverter recovers the room quickly. Use the timer to start it 20 to 30 minutes before you get home.
What size split system do I need?
Roughly 100 to 140 watts of cooling per square metre in a typical insulated room, so a 25 m² bedroom suits 2.5 to 3.5 kW and a 50 m² living area suits about 5 to 7 kW. Hot west-facing rooms and high ceilings need more. The size calculator does the maths.
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