Air conditioning

Last updated: 7 December 2022

Refrigerative air conditioners remove heat from the air inside your home and transfer it outside, cooling the air to a temperature determined by a thermostat. They cool, dehumidify and recirculate room air. Unlike evaporative cooling systems, as long as they are sized correctly, they work effectively in any climate. Most modern air conditioners are reverse cycle, meaning they can be used to both heat and cool your home.

Types of air conditioners

large white air conditioner mounted on wall

Window/wall units – designed to cool a single room or open plan area. These units are cheap to install but have limited application as they are only suited to smaller rooms. Installation into windows can negatively impact natural ventilation strategies, and units should not be installed into the only opening window in a space.

Split systems in a single room or with multiple outlets – have a separate indoor air handling unit and an outdoor compressor unit (heat pump) connected by refrigeration piping, keeping most of the noise outside. Most commonly these indoor units are wall mounted, however, more discrete options are available including bulkhead units, where only a grille is visible, and ceiling cassette units, which are recessed into the roof space. These systems can meet both your homes heating and cooling needs.

Ducted systems which cool the whole house through multiple ceiling outlets – have a central air handling unit that is usually located in the ceiling space and a single compressor unit (heat pump) located outside, connected to the air handling unit by refrigerant piping. These systems can meet both your homes heating and cooling needs.

Running costs

Inverter air conditioners have a variable speed (or inverter-driven) motor. Rather than switching the compressor on and off, they automatically vary the speed of the compressor, running it at full speed when cooling demand is high and at a much slower speed when cooling demand is low.

Inverter air conditioners are quieter to run and have lower running costs compared to the standard air conditioners. Most modern split system air conditioners are inverters.


The best way to ensure that you have the right-sized unit is to have a full heat load calculation carried out by an authorised air conditioner installer or manufacturer before you purchase. This is best done in your home so that factors such as ceiling heights, window sizes and orientations, and insulation levels can be taken into account.

If your system is too big for the space it is cooling, it will have short cooling cycles (switching on and off) resulting in increased power consumption and excess wear and tear on your unit. This is likely to be a greater concern with standard air conditioners than with inverter models.

If your system is too small, it won’t provide adequate cooling. This will result in the unit working harder than it is designed for, increasing maintenance requirements and potentially shortening the life of the unit.

If you have a split system servicing a single room in your home, it is important to ensure this space is zoned adequately with doors closed to prevent cool air escaping and the unit working overtime in an attempt to cool the space.

Choose energy-efficient cooling

Once you’ve established what size you need, use star ratings to choose an energy-efficient cooling system for your home and learn how to use your cooling system efficiently to save even more energy and money.