Start with your climate, then the number of rooms you want to condition, then the capacity those rooms need. Efficiency, noise, brand and the installer come after that.
Most people start by asking which brand is best, which is the wrong first question: a well-sized, well-installed mid-range system will beat a premium system that is the wrong size or badly fitted, every time. Work through these seven factors in order.
1. Your climate
Climate decides the system type before anything else.
- Humid summers (Brisbane, Cairns, Darwin, coastal Sydney): refrigerated air conditioning. Evaporative cooling loses effectiveness as humidity rises
- Hot, dry summers (Perth, Adelaide, inland areas): evaporative cooling is a genuine option and much cheaper to run, though it cools only
- Cold winters (Canberra, Tasmania, the Southern Highlands, alpine areas): a reverse cycle system, and check its performance in the cold climate zone rather than the average
The Zoned Energy Rating Label rates air conditioners separately for three climate zones: hot, average and cold. Use the Energy Rating Calculator to find your zone, then compare models on the rating for that zone rather than the headline number.
2. How many rooms you want to condition
This is what decides between system types and it largely decides the budget.
| Areas to condition | Usually the best fit |
|---|---|
| One room | A single split system, or a window unit if a split is not possible |
| Two or three areas | Separate splits, or a multi-split |
| Four or more areas | Ducted, or a multi-split if ducting will not fit |
Three areas is genuinely a close call. Ask your installers to quote both ways.
3. Capacity
Capacity is measured in kilowatts (kW) and it is the single most important number in your quote.
Undersized, and the system runs flat out without reaching temperature, which shortens its life and costs you money. Oversized, and it short-cycles, costs more up front, dehumidifies poorly, and still costs more to run.
Capacity is not just about floor area. Ceiling height, insulation, window size and orientation, roof type, and how many people use the room all change the answer. That is why a proper heat load assessment beats any online calculator.
4. Energy efficiency
Heating and cooling account for around 40% of household energy use in the average Australian home (YourHome). The efficiency of the system you choose will follow you around for the next decade or more.
Single-phase, non-ducted air conditioners up to 30kW must carry a Zoned Energy Rating Label in store. It gives you:
- A star rating from 1 to 10 for cooling and for heating, in each of the three climate zones
- Estimated annual energy use in kilowatt hours, which you can multiply by your electricity tariff to estimate running costs
- Heating and cooling capacity in kW
- Noise levels in decibels, indoor and outdoor
Ducted systems, three-phase systems, multi-splits and evaporative coolers are not required to display the label, though some manufacturers do so voluntarily. Where there is no label, ask your installer for the performance figures in writing.
One useful rule: only compare star ratings between systems of similar capacity and type. A 5-star 13kW system uses much more electricity than a 5-star 5kW system.
5. Noise
Noise is the complaint people raise most often after installation, and it is the easiest thing to check beforehand.
- Indoor noise matters most in bedrooms and studies. Look at the decibel figure on the energy label, and ask to see the unit running in a showroom if you can
- Outdoor noise matters for your neighbours. Most councils have noise limits for air conditioner condensers, especially at night. Ask your installer where the outdoor unit will sit and whether it complies. Getting this wrong can mean moving the unit at your own cost
- Evaporative coolers generally produce more indoor noise than refrigerated systems, particularly at higher fan speeds
6. Brand and warranty
Once you have the type and capacity right, brand becomes a question of warranty, parts availability and service network rather than performance.
Look for:
- The length of the manufacturer’s warranty, and whether it covers parts and labour or parts only. Five years parts and labour is common on major brands
- A separate installation warranty from the installer
- Whether spare parts and service agents are available in your area, which matters more than the brand’s global reputation
7. The installer
A good system badly installed will underperform for its whole life. Refrigerant charge, pipe length, drainage fall, duct sealing and outdoor unit placement all affect how well it works and how long it lasts.
In Australia, anyone installing or servicing a refrigerated air conditioner must hold a Refrigerant Handling Licence from the Australian Refrigeration Council, and the electrical work must be done by a licensed electrician.
How to choose a reliable installer · Questions to ask your installer
Before you sign anything
- Get more than one quote, and make sure each is for a comparable system
- Insist on a site visit and a heat load assessment, not a quote based on floor area
- Check what is included: electrical work, duct sealing, dampers, commissioning, warranty registration, removal of the old unit
- Ask what could add to the price once work starts
- Do not sign on the day. Any installer pressing you to is telling you something