What Size Air Conditioner Do I Need?

Installing an air conditioner is an expensive, long-term investment so taking the time to make the right decision is super important. The size unit you will need is determined not only by the size of the room but also how well insulated it is, its orientation and your location. Making the right choice now is key to maximising the unit’s performance while also minimising running costs.

So, how can you determine what size unit will be right for your needs? Let us talk you through it.

Room Size

Measuring the length and width of the room is great but to get an accurate gauge of how much power will be required to cool the room you will need to know the ceiling heights so you can calculate volume.

Here is a rough guide to the air conditioner size you will need to cool a particular room size:

Room SizeExampleApprox. capacity
Small (up to 20m2)Bedroom or study2-2.5kW
Medium (20-40m2)Bedroom w/ensuite, small lounge room2.5-5kW
Large (40-60m2)Large bedroom or medium size lounge room4-6kW
Extra Large (60+m2)Open plan areas or large lounge rooms6-9kW

Using this guide, you should have a rough idea of what will work well in your space. Don’t be tempted to go too small to save money or too big to keep your room like an igloo as this can cost you money in the long run. An incorrectly sized unit will end up increasing your power usage as well as both will experience more wear and tear on the unit.   


Where you live in Australia will impact the size air conditioner unit you need. For example, a room in Darwin will need a much bigger unit than the same size room in Hobart. In Brisbane, a 30m2 room will typically need a 2.2kW unit.


Are the walls and ceilings of the room you want air conditioned insulated? Ceiling insulation is one of the biggest factors when it comes to create a thermally efficient home. If your ceiling is currently insulated, we recommend that you consider installing it. It will save you money in the long run as you will be able to install a smaller unit and minimise your ongoing running costs.


Another thing to consider is the orientation of the room in your house and how much sunlight it gets throughout the day. A large north or west facing window can let in a lot of summer heat whereas windows on the south of the house will mean the room is cooler. You can help to reduce the costs of running an air con in a north or west facing room by pre-cooling however a bigger unit may be needed to efficiently cool the room.

Get in touch for Expert Advice

At Dawson Electric, we understand that there are so many things to consider when deciding on what air conditioner will be right for your home or office. Get in touch with our friendly team so that we can help determine the right size air conditioner for you.

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