How do I choose the size of my split system?

Air Conditioning FAQs

Buying an air conditioning unit is a significant investment costing up to thousands of dollars, with a lot of facets to consider. Now that you’ve decided on a split system, before you make your purchase, you need to figure out the optimal size of the split system that will suit your home. In other words, you need to ensure that you choose a split system with an appropriate strength in kWs, which will best suit your space.

An important first step is to consider what kind of space your split system will be covering.

Don’t worry if maths isn’t your strong point, we’ve got you sorted with some advice and check lists to make sure you get the split system you need.

First thing’s first: How big is the space you want to cool or heat?

To work this out you’ll be looking to find a size in square metres. Go room to room in your house or office with a tape measure and do this simple equation:

Length of room multiplied by width of room

Add the sum for every room together and you can then start looking at which size air con is most appropriate. That seems easy enough, right?

If you don’t have a tape measure, we’ve included below an image that you can use a bit of a cheat sheet for approximating the squire meterage of your room

But why does the kW capacity of my split system matter?

Most consumers are looking to improve their comfort level by controlling temperatures in their homes without increasing their energy costs. A powerful unit in a small space may lead to an overly cold or hot environment whilst a unit with moderate power may fail to cool down a large space; it’s all about getting it right for your space and preferences, as well as not wasting energy.

Where do I find the kW measure?

Most units should have a label letting you know the cooling or heating output. Don’t be afraid to ask for assistance from your air conditioning installer if you can’t find it in your research.


How do I know how many kWs will I need?

Split systems come in different kW strengths. The most common strengths are: 2.6 kW (killowatts), 3.5 kW, 5 – 6 kW or 7-8 kW. To figure out which one is most suited not only will you need to consider the size of your space as above but also:

  • The climate you live in (is it humid, dry, etc?)
  • How big are the windows and doors in your space?
  • Is the space open plan?
  • Do your internal doors have any gaps allowing hot air from another room to infiltrate?
  • Which way do your windows face? If it’s west you’ll need more power to compensate for the power of the summer sun.
  • What kind of curtains, blinds, shutters, trees etc do you have?
  • Do you have insulation?

With an expensive outlay it’s always important to do your own research. You can start by answering the above questions and move onto a shorter list of options from there.

Now you’ve gathered all your information you should be able to figure out which size will suit. The basic rule of thumb will be – the bigger and more poorly insulated the space you want to cool, the higher the number of kWs you will need from your unit.

How many kWs for which space?:

If we break it down into room size, from smallest to largest:

  • Small spaces/rooms (0 m2 – 15 m2); 2.6 kW is generally a good capacity for smaller spaces, say an inner city flat or small studio apartment. It should cover, for example, your lounge room, studies, small bedrooms, the laundry or a children’s nursery.
  • Medium Rooms (15 m2 – 30 m2); In this size you’ll be looking at 3.5kW which should cover larger variations of the examples above including a small lounge room that might need a stronger output (for example, one that’s west facing with full length windows), bedrooms with an attached bathroom and medium kitchens.
  • Large rooms (30 m2 – 60 m2) A 5-6 kW unit covers larger bedrooms, kitchens and study rooms/offices and, medium-sized lounge rooms. Say, a family home on the larger size.
  • Really really large (60 m2 – 80 m2); If you have a lot of space or are looking to cover an open plan area like a repurposed factory floor apartment, you’ll be looking at a big 7 – 8 kW monster to keep you cool.

That seems pretty simple. Do I need to consider anything else?

When you have matched your space to the appropriate kWs it is suggested that you be sure to choose one with an equal or slightly greater strength. So if you’re in a small apartment, you could go up to a 2.8 if you think you’ll need it. Don’t go any lower though or you’ll risk pushing the unit above its capacity and causing it to age quickly.

Don’t forget to consider operational costs. Air conditioning systems take up a fair amount of our utility bills. You can find a more energy efficient model by using the star system – the more stars, the more efficient (including models with a higher kW). That’s good news for your bank balance.

With the compressor usually installed about 15m away a split system unit is lovely and quiet, with the capacity to cool several different rooms. Once you’ve chosen the right unit for you it will be time to sit back, relax and enjoy your new air conditioning system.


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