Air conditioning

Last updated: 6 September 2022

How do air conditioners work?

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. However, they are the most expensive form of cooling system to purchase and operate.

Types of air conditioners

Window/wall units – designed to cool a single room or open plan area.

Split systems in a single room or with multiple outlets – have a separate indoor air handling unit and an outdoor compressor unit connected by refrigeration piping, keeping most of the noise outside.

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 located outside, connected to the air handling unit by refrigerant piping.

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 split system air conditioners these days are inverters.

Sizing an air conditioner

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.

Choose an energy-efficient cooling system

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