The Australian summer can be both beautiful and brutal. Nothing quite prepares you for those 40+ degree days, so having a good air conditioner is a no-brainer. But don’t forget to invest in regular maintenance throughout the year so you don’t have to worry about it breaking down once the temperature rises – and when you need it on for hours.

Have you thought about adding another system in your house? Maybe you want to replace an old one or extend your living area and renovate your space. It’s good to know what size will best suit, so you can cool (and heat) the room without paying through the roof for it.

Air conditioner sizes for rooms: The formula

Air conditioners run best when they’re matched to the spatial conditions. If the system is too large, it’ll cool your house quickly and then turn off without going through its entire cycle. The house will heat up again and follow the same process, on-again, off-again, which chews up power. On the other hand, if it’s too small, it’ll need to stay in overdrive just to cool the space.

There’s a formula to use as a guideline to help you decide which size air conditioning system you should buy. It’s a great way to get an idea of what you need. To start, first you’ll need to know the dimensions of the room.

Once you know the length and width of each room, multiply them. Then, add the area of each room together for the total area of your house. This figure needs to be in square metres.

 The ceiling height matters. Here’s why:

  • If your ceiling is 2.4m high, you will need to multiply the daytime living area (m²) by 150 (watts).
  • If your ceiling is 2.7m high, you will need to multiply the daytime living area (m²) by 160 (watts).
  • If your ceiling is 3m high, you will need to multiply the daytime living area (m²) by 175 (watts).

 Once you know the calculations, it’ll give you the number of watts you need. Then, just move the decimal point three points to the left to convert it to kilowatts. For example, let’s say your house has a daytime living area of 100m² and a height of 2.4m, the calculations would be:

  • 100m² x 150 watts = 15,000 watts
  • 15,000 watts = 15 kilowatts

 A 15kW unit is roughly the right size for this house.

While this is a great way to self-educate, the best way to get it perfect is to get a professional to come in and calculate it. If maths isn’t your thing, skip the guesswork and call us at AEPER.