General information, not technical advice; no brand or model is named here. Your Home and energy.gov.au, linked at the foot of this page, are the official guides to heating and cooling a home.
The main types side by side
| Type | How it cools | Where official guides say it suits | What to weigh |
|---|---|---|---|
| Split system (wall unit) | An indoor unit joined by refrigerant pipes to an outdoor compressor. | Cooling the rooms you use; energy.gov.au calls non-ducted splits the most efficient option. | Quieter than older box units, Energex says, but performance and noise vary a lot between brands and models. |
| Multi-split | Two or more indoor units on one outdoor compressor. | More than one room served from a single outdoor unit. | Energy Rating says the outdoor unit is what gets registered, so it may be sold with different combinations of indoor units. |
| Ducted | A central unit, usually in the roof, sending air through ducts to outlets around the house. | The whole house from one system; Energex says it is easier and cheaper to fit when building or doing a major renovation. | Less efficient, because fans must push air through the ducts. Zones that switch off unused areas can help. |
| Window or through-wall | Everything in one box, set into a window or an outside wall. | Single rooms or small areas, as its output is lower than a similar split’s. | Larger ones may need a dedicated electrical circuit installed. |
| Portable | A freestanding unit, with a duct to release hot air outside, usually through a window. | Single rooms up to about 50 m², Your Home says. | Less efficient than fixed splits; a single duct model shows no stars on the label. |
| Evaporative | Outside air passed over water, cooled as the water evaporates, and blown through the house. | Drier inland climates; Energex says generally not humid ones. | Needs windows or doors open, and uses water. |
Reverse cycle: one system for both seasons
A reverse cycle air conditioner is a heat pump that warms a home in winter and cools it in summer. Your Home calls it “the most energy-efficient heater and cooler of all types, irrespective of fuel source”. It adds that even units with lower ratings, around 2 to 3 stars, are significantly cheaper to run than other heating and cooling appliances.
Inverter technology lets the compressor run at variable speeds depending on the output needed, energy.gov.au explains, and Your Home says inverter systems with advanced design can save 40 per cent or more energy compared with standard units.
If you are weighing ducted
Energex notes that one ducted system can cool the whole house, but can cost more to install than several split systems and needs more energy to run. Your Home sets out what makes ducts work well:
- ducts that are insulated and sealed, ideally inside the cooled space, with straight runs and tightly taped joints;
- ducts of the correct size, with adjustable outlets, and larger if they also carry cooling;
- a way for air to return from every outlet to the central unit, such as a gap under each door;
- design and installation by accredited experts.
If you are weighing evaporative
energy.gov.au says ducted evaporative coolers use less than half the electricity of an air conditioner of similar capacity, balanced against weaker cooling on humid days and water use of up to 25 litres an hour. Your Home adds that because they bring in large volumes of outside air, you may need to limit their use when that air is poor, for example during bushfires. In winter, built-in coolers can lose warm air through their ducts unless they seal or the ducts are closed off.
Portable evaporative coolers are less effective, energy.gov.au says: recirculating indoor air and adding moisture, they may start to warm the room unless air can flow outside.
Before any of them: a fan
Your Home says ceiling fans should be your first choice for keeping cool, because they cost little to run and use less energy than an evaporative cooler or an air conditioner. Fans do not cool the air; the air movement makes people feel cooler. How fans and air conditioning work together is in the setpoint and running costs, and how big a system to buy is in sizing a system for a room.
Which type suits depends on the house, the climate and the rooms you use. Your Home says “fixed systems need to be installed by a licensed refrigeration mechanic or electrician”, and that the installer needs to hold a Refrigerant Handling Licence, so a licensed installer who can see the house is the person to compare the options with.