What Size Air Conditioner Do I Need?

Is it getting hot in here?

Why not get an Air conditioner? What size air conditioner you ask, well, get the one that’s best for you. Or better yet, let the Air Conditioner installer decide it, they are pros so they know what they are doing. Helpful, wasn’t it?

If you are tired of such “all-encompassing” advice, can we offer you some instead? We promise, these are based on our professional expertise and will help you determine the “right” air conditioner for the location of your choosing in Australia. It can be your house, office, or shop; what all of these locations have in common is space, and you will be choosing your Air Conditioner based on factors covering aspects that will help keep those spaces cool and/or air-conditioned. 


Before we move forward, there are a few factors that you need to take into account prior to deciding on the right size of Air Conditioner. This includes the location or the orientation of the space, how well it is insulated (more important than you think!), its size, and if there are any devices that are generating heat in that space. For instance, in Australia, you can have a studio apartment with a fridge, stove/microwave, computer, high wattage lights, washing machine/dryer, and dishwasher among other things. They can generate a significant amount of heat to keep a space warm.

Choosing the right sized Air Conditioner not only requires factoring in the heat produced by these appliances but also the size and number of windows, along with the amount of sunlight space receives which can be a bit too much in Australia, Melbourne. All of these complex calculations will allow you to receive maximum comfort with minimum running costs. Additional variables that need to be considered as well include:

  • The climate – How hot or cold is it where you live in Melbourne. If you live in an area with moderate temperature, you will most likely not need an Air Conditioner with higher wattage. If it’s too hot or too cold there, your Air Conditioner wattages may go up significantly. 
  • Orientation – If your windows face north or west, they can let in a lot of heat during summer which may call for additional cooling. Similarly, if a room with poor insulation faces a lot of sunlight despite not having any windows, it may still overheat.  
  • Roofing Material – If your roof has tin roofing, the area under it can get significantly warm. Tiles on the other hand provide a great degree of insulation.
  • Number of People – Yes, this too is a variable when it comes to cooling. More people mean more heat, so you naturally need more cooling.

Simple DIY Calculation:

As a rule of thumb, consider anywhere from 120 to 150 watts of power for every square meter of floor area.  So here’s a simple equation to help you calculate the right wattage of Air Conditioner for your floor space; simply put the variables in the equation given below.

(floor space) x (150) = required wattage for AC

For instance, if the maximum floor area of the area you wish to keep cool is around 20 m2, then:

20 x 150 = 3KW.

This is the required wattage that should provide you with the optimum cooling/heating required. Do keep in mind that still have to factor in the aforementioned variables that can demand an increase in cooling requirement. Similarly, if the area you wish to cool (or heat for that matter) has poor insulation, you will have a hard time maintaining your desired temperature. 

Similarly, areas with high roofs also need to be considered as a variable when calculating the right size of Air Conditioner, seeing as they require more power for their temperature to be regulated. 

How To Factor In the Variables:

So, now that we know how to calculate Air Conditioner power based on floor area, how do we factor in those tons of variables we discussed above? Well, for starters, the more of the variables you have, the more Air Conditioner power you will be needing. Especially for the Australian outback.

  • If you have your living space packed with the aforementioned variables, you are automatically in need of 1-1.5 extra KW. 
  • If the amount of the variables is mediocre/moderate, add in 1-0.5 a KW.
  • If the amount of variable is close to the bare minimum, there’s no need to add in any extra wattage. But there’s a tip just ahead that might provide you benefits in long run.

Does Size Really Matter?

Yes, it does! If you have that bigger is better mindset, be sure to face a bigger electricity bill; and if you are one of less won’t mess people, wait till you pay for the maintenance bill after regular breakdown of your Air Conditioner. A common dilemma faced by Australian commoners; especially people living in Melbourne.

If the Air Conditioner is too big:

  • The power use will increase.
  • Space may get too cold or too hot.
  • An obvious increase in running cost.
  • The Air Conditioner will run short frequent cycles so you won’t be able to get your desired temperature.
  • This also means the room won’t humidify properly.

If the Air Conditioner is too small:

  • The unit will be overworked.
  • Your unit will face more wear and tear on regular basis. 
  • It will consume more power.
  • Running at maximum capacity means it will dry out the air.

Here’s a piece of professional advice, although bigger is not better, but slightly bigger is the best. In case your living space has a need for 5KW Air Conditioner, opt for 5.5KW instead. You can thank us later.


Choosing the right sized Air Conditioner in Australia is serious business; if you too need to have just the perfect Air Conditioner selected for a particular space, we hope this guide will suffice. Or, you can opt for our services, and let us do the job for you. 

At ComfyHome, we have years of experience pertaining to the installation and repairing of Air Conditioners in Melbourne Australia, this also includes helping our clients determine the right size of Air Conditioner they need. So reach out to us whenever you need to and we’ll make your home ‘just comfy’ for you!

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