Split system air conditioning: sizing and costs
How to size a split system air conditioner for each room, and what installing splits in three rooms costs in Australia, from multi-head to concealed units.
Installing a separate reverse-cycle split system in each of three rooms typically costs $9,000 including GST, with most quotes between $7,000 – $11,700. A multi-head system with one outdoor unit serving all three rooms comes in around $4,650, and concealed ceiling-recessed units about $17,500. Getting the size right matters as much as the price: an undersized unit runs flat out and still struggles on a hot afternoon, and an oversized one costs more to buy for no benefit.
Sizing: how much capacity each room needs
Split systems are rated in kilowatts (kW) of cooling capacity. As a starting point:
- Bedrooms and studies are usually covered by units of 2.5–3.5 kW.
- Larger bedrooms and small living rooms often need around 3.5 kW.
- Open-plan living, kitchen and dining areas often need 5–8 kW, sometimes more.
Floor area is only the start. Push the size up for:
- West-facing rooms that take the afternoon sun, and rooms with large windows or no eaves
- High or raked ceilings, which add volume to cool
- Poor insulation, especially under a dark roof or in an older home
- Hot climates: a room in Darwin or western Sydney needs more cooling than the same room in Hobart
- Kitchens and rooms with lots of people, which add heat
Push it down for well-shaded, well-insulated rooms. A good installer should look at each room before recommending a size, not just ask how many square metres it is. Reverse-cycle units heat as well as cool, so in cooler states check the heating capacity too, which is listed separately.
What it costs: three options compared
| Option | Typical price, three rooms | Usual range |
|---|---|---|
| Multi-head: one outdoor unit, three wall units | $4,650 | $3,650 – $6,050 |
| Separate split in each room | $9,000 | $7,000 – $11,700 |
| Concealed ceiling-recessed units in each room | $17,500 | $13,600 – $22,700 |
Multi-head saves on outdoor units and wall space, and the price reflects that. The catch is that every room depends on one compressor: if it fails, the whole house is without cooling.
Separate splits run independently. If one breaks down, the others keep working, and each can be sized exactly to its room. This is our mid-range option and the most common choice.
Concealed units sit in a plasterboard bulkhead with only a grille showing. They look tidy and run quietly but cost considerably more to buy and install.
For one room or five, change the number of rooms in our Split system air conditioning.
What the mid-range price includes
- One 3.5 kW reverse-cycle split system per room, each with its own outdoor unit
- Wall-mounted indoor unit, core hole through the wall, vacuum and commissioning
- Pre-insulated copper pipe, about 5 m per unit
- A condensate drain for each indoor unit
- A dedicated circuit with its own breaker and cabling in conduit for each outdoor unit
- Outdoor unit bracket and connection
Not included: condensate pumps where water cannot drain by gravity, special roof or wall supports, patching and painting around wall penetrations, and a switchboard upgrade if yours has no room or still has ceramic fuses.
We build each price from the equipment and the hours an air conditioning installer and electrician need, at local labour rates in your state, and check the result against market prices and real quotes.
What pushes the price up
- Long pipe runs. Our price assumes each indoor unit is within about 5 m of its outdoor unit, ideally back to back on an external wall. Running pipes through the roof space or down a two-storey wall adds labour and pipe covers.
- Access. Outdoor units on a roof, a high wall or a narrow side path take longer to install.
- The switchboard. Each outdoor unit needs its own circuit. An old board may need upgrading first.
- Bigger capacity. A 7 kW living-area unit costs noticeably more than a 3.5 kW bedroom unit, both to buy and to install.
How to save
- Keep pipe runs short. Put outdoor units directly behind the indoor units on an external wall where you can.
- Size each room separately. Do not buy the same large unit for every room.
- Prioritise. Cover the main living area and main bedroom first, and add the rest later if needed.
- Book outside peak season. Installers are busiest during summer heatwaves; autumn and spring are usually easier to book.
Licensing and your quote
Connecting air conditioning is electrical work and must be done by licensed tradespeople under state licensing, and the refrigerant work needs a licensed technician too. Ask for licence numbers on the quote and the electrical compliance certificate when the job is done. Quotes to households include 10% GST, and so do our figures.
Once you have a written quote, check that it lists the model and capacity of each unit, then compare the total with typical prices in your state using our "Is my quote fair?" tool: Is my quote fair?.