Air Conditioning Brisbane – Sales, Installation and Servicing Specialists

Air Conditioner Size Guide

What size air conditioner do I need?

Our Simple Air Conditioner Size Guide / Calculator​

Choosing the right air conditioner size for a given room size is very important if you want to minimize your electricity bill. Use our air conditioning sizing guide Australia to search for the right kw rating size for your area. A small air conditioner will have a hard time cooling a large room, or it might not be able to cool it at all. On the other hand, choosing a huge air conditioner could cool the room very fast, but will not dehumidify the room at all. This leaves the room cold and, at the same time, humid, which is not comfortable at all.

Another problem we have see is the air conditioner is so big that the thermostat does not have time to correct the temperature properly and leaves the room very cold. Therefore, it is crucial to decide what kw rating or sizing of aircon you need before buying one.

You can use a fancy Split system air conditioning sizing calculator but we have made it easy and strait forward with out sizing guide.

There are four main classes that affect how big your Air Conditioning needs to be, to effectively cool the area you wish to air conditioning.

A Class

Air Conditioning in a home with Insulated roof space, walls and sub floor, full brick or brick veneer construction, average size windows with awnings, full shading south facing aspect, temperate weather conditions.

B Class

Installing aircon in a home with insulated roof space, full brick or brick veneer construction, average size windows with internal shades, north facing aspect, temperate climate.

C Class

Cooling your home with Insulated roof space, full brick or brick veneer construction, average size windows with internal shades, east facing aspect or sub tropical climate.

D Class

Running AC with little or no insulation, weatherboard, fibro or brick veneer construction, large windows, no shading from the sun westerly facing aspect.


Room size - Area

The first is obvious, the area of the room.  This is calculated by length x breadth.  Say for a normal bedroom size 4m x 4m = 16sqm .   You would look at the table above and see that a 2.5kw unit will be sufficient most the time, unless you have a fibro, un insulated house, than you will need a 3.5kw as the 2.5kw will no cool to the desired temperature and will use a lot of power trying.


Air Conditioner size guide Australia
insulation to help with air conditioning sizing guide


Is your ceiling space in your home insulated and what kind of insulation is installed?  There are many different installations with many different ratings.  if your home was insulated during the insulation batts scheme, your roof space might as well not have insulation at all.  This was highly unregulated, and some people even found the rolls of foil insulation just thrown up in the roof not even installed.   You will have the double check that you have the proper insulation installed.  The rating for Brisbane is R4.1   in the ceiling and R2.8 within the wall.  You should get a professional to check and see what you have.


location also makes a big difference.  If you’re located on the Bay side and get a nice bay breeze every day,  your property is going to be a lot cooler.  If you are located inland somewhere like the North side of Ipswich where it generally is a lot hotter,  you will require a more powerful Air Conditioner to fight the extra heat load.  Have a look here at the temperature map of qld to help understand

qld temperature map
orientation affects sizing calculation of air conditioner size


The orientation of your room also affects the cooling capacity of the area. for instance, if you have a long living room with big glass sliding doors and windows along the northern face you are going to be getting a lot of that summer heat coming through with the sun shining most of the day on the northern walls and windows whereas if you had a southern facing living area, you would be much cooler as you are not getting any sun shining through the windows or on the walls generating heat

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