When shopping for an air conditioner there are two main types that are installed in Australian homes, evaporative air conditioners and split system air conditioners.
Factors that should be considered when deciding between an evaporative or split system air conditioner is the size of your home, the cooling capacity of the unit, climate, installation, running and maintenance costs.
Evap air conditioning suits a specific use case and should not be directly compared to refrigeration air conditioning units in all situations.
Humidity is the biggest factor when deciding whether evaporative air conditioning is suitable for you. If you live in a high humidity area then evaporative air conditioning isn’t an options. Evaporative air conditioning works by running water over filters and using a fan to draw air through the filters into the house evaporating the water and cooling the air. This process does not work well in areas with high humidity.
This map from the Bureau of Meteorology shows the climate and humidity across the Australia continent. If you live in any of the high humidity zones like Brisbane or Darwin then evaporative cooling will not be an option.
Evaporative cooling is most appropriate in the southern parts of Australia such as Melbourne, Adelaide and Perth and the dry inland areas like Canberra, Mildura or Alice Springs.
The cost of running the air conditioning unit is a major consideration for most buyers when selecting a unit.
A quick example of the cost comparison between the two types of units:
With an example electricity price of $0.30 kW/hr comparing an evap and a split system running at full capacity.
$1.50 per hour
60 litres water per hour @ about $3.25 per kL = $0.20
Electricity usage by fan at 0.75 kWs $0.225
Total of $0.425 per hour
In this example, the evaporative cooler uses about one third the amount of electricity of the split system.
Over 100 hours this works out to a difference of $107.5 in running expenses. In a hot period, this could be as little as one week of usage.
Split system air conditioners don’t work efficiently if you leave windows or doors open, so if someone in the family is a big fan of fresh air, and you’re a big fan of cool air, then split air isn’t necessarily going to be your best bet.
A standard back-to-back split system installation including wiring and appropriate permits can vary quite a bit depending on season and quality of work. You may find them cheaper but you get what you pay for. The potential exists for a poor installation to cause expensive repair costs down the track and that should be considered. A non-standard split system installation with brackets, ductwork, a long run, or additional power requirements will obviously cost more. All split system installers in all states are required to be licensed by the Australian Refrigeration Council and the person doing the wiring needs to hold a restricted electrical licence at a minimum.
Multi-head split system units have one single condenser and multiple heads inside the home. A multi-head unit is an option for cooling multiple rooms with refrigerated air conditioning.
They are the best option for whole house cooling where you can’t run ductwork, for example, a slab floor with a flat or cathedral roof.
For an evaporative air conditioner to be most effective they require windows or doors to be open to allow airflow. As a guide, the entire volume of the room should flow through every two minutes (or around 30 air changes per hour).
During winter, older ducted units on the roof should have covers placed over them and ceiling vents closed to stop heat loss. Most new units have an automatic spring or gravitational shutter.