What size air conditioner do you need in Australia? (2024)

Anula Wiwatowska
Nov 08, 2024
Icon Time To Read3 min read
// Brrr, its cold in here

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If you're looking to chill out during the warmer months there are plenty of factors to consider in your air conditioner. The first one you need to tackle is what size aircon you need.

The higher the cooling capacity, the more powerful the air conditioner, and therefore the more space it can cover. But bigger doesn't neccessarily mean better, especially if running costs are an important consideration in your household.

You'll need to consider not only the wattage of the aircon, but also room size, insulation, windows, and ceiling height. It is a lot to think about, but we'll help make the process that little bit easier.

The basics

Every room is going to be different, and while there is a lot that goes into picking the exact right wattage of your air conditioner, having a general idea can be a good starting point.

At its most basic, you'll want to account for 125 watts of cooling capacity, for every square metre in the space. So a small room of around 20m2 would need a 2.5kW cooling capacity, while a larger space of 60m2 would need closer to 7.5kW.

It is important to make sure that the number you're looking at is in fact the cooling capacity, and not the input wattage. The input wattage tends to be lower than the cooling capacity thanks to how high efficiency these devices are. But mixing up the two could result in not only an air conditioner that is too powerful for the space, but also a higher electricity bill than neccessary. 

Room size
Room type
Cooling capacity
20m2Bedroom or study2.5kW
40m2Master bedroom or sitting room5kW
60m2Open plan dining and lounge or large landing spaces7.5kW

Climate considerations

Depending on where you live, the same kilowatts of cooling capacity will be more or less effective. In Mild zones up north the air conditioner has to battle higher heat and humidity, and therefore needs to work harder than it would in Cool or Cold zones like Victoria and Tassie.

The 125 watts of cooling capacity per square metre we mentioned earlier, shifts depending on where you're located in the country. Here's how that breaks down according to Fair Air's calculator.

Location
Watts per m2
Capacity for 20m2
Sydney801.6kW
Brisbane961.9kW
Darwin1162.3kW
Perth1262.5kW
Adelaide1102.2kW
Melbourne1102.2kW
Hobart601.2kW
Canberra1061.2kW

Building considerations

How your home is built plays a vital role in keeping it cool, and how much cooling efficiency you'll need. Everything from the floor type, to the roofing, to window size and coverings, and even the position of the room itself within the home will play a part in how much capacity is required to cool it down (or heat it up for that matter).

For example, a 20m2 room is Sydney in a weatherboard house with no insulation, wood floors, and a tin roof, with two large east facing windows requires 3.4kW to adequately cool it. With roof insulation this goes down to 3.3kW, and with wall insulation it drops to 3.2kW.

While a whole new roof or floor might not be in the budget, there are cheaper ways to lower the cooling load of a room. Adding high quality, external window shades can keep the heat out. Internal shading like blinds does help a little bit, but they still allow a lot of the heat to permeate the room before it is blocked. You an also fill up gaps and holes around windows, doors, and floors.

Is bigger better?

Finding the right air conditioner size really is a Goldilocks situation. You don't want something too big and is going to cut into your budget, and leave you uncomfortable. But you also don't want something too small which will ultimately do the same thing but in a different font. You're really looking for your bowl of porridge, or your glass slipper.

While we can give you some solid ideas as to the size you'll need, your best bet is to go through a detailed calcultor like the one found on Fair Air. This takes everything we have covered into account, and can even give you an idea of what else you could do to bring down your current cooling requirements.

Of course you may not be able to find an air conditioner that is the absolute perfect size, and if that is the case we do recommend going slightly larger than you'll need. While there are trade-offs like higher power usage, and lacklustre dehumidification, they're generally better than what you'll experience with units that are too small. Smaller units usually need to run at a higher capacity for longer which can in turn dry out the air, increase your usage costs, and put more pressure on the system leading to a shorter shelf life.

Anula Wiwatowska
Written by
Anula is the Home and Lifestyle Tech Editor within the Reviews.org extended universe. Working in the tech space since 2020, she covers phone and internet plans, gadgets, smart devices, and the intersection of technology and culture. Anula was a finalist for Best Feature Writer at the 2022 Consensus Awards, and an eight time finalist across categories at the IT Journalism Awards. Her work contributed to WhistleOut's Best Consumer Coverage win in 2023.

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