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A Guide to Properly Sizing a Split System Air Conditioner for Your Space

When it comes to selecting your air conditioner, choosing the right size is the most important decision you will make.

Having the right size of air conditioner gives you plenty of benefits, from properly cooling your room to helping you use energy efficiently. However, if you Google the correct aircon sizing for your space, the answers you find may intimidate you, most likely due to the numbers and calculations involved. But don’t worry; we are here to make the entire process straightforward for you. This blog helps you determine the best size of a split system air conditioner in the simplest way possible.


The Impact of Undersized and Oversized Air Conditioners

Air conditioner malfunction happens too often in West Australian homes. Fortunately, the issue is easy to solve because it is mainly associated with installing the incorrect aircon size.

Indeed, an undersized aircon will still work for the space, but not to the degree you expect. You will almost instantly notice that it fails to deliver a comfortable temperature, which typically means you must keep it running constantly. Even so, your home may not feel cool enough. Additionally, cooling will be uneven, where some portions of your home feel cooler than others.

Oversized air conditioners, on the other hand, may appear to be a better option than undersized ones. But that belief is far from the truth. In reality, an oversized aircon will be subjected to quick on-and-off cycles. Although it is nice that it takes a short time to cool your house, it also means that the appliance undergoes several on-and-off cycles, causing it to shut off and run again numerous times. You can already tell the aircon will be more susceptible to wear and tear.


Determining the Cooling Capacity Required

A space’s cooling load refers to the air conditioning unit measurement needed for cooling, often expressed in kilowatts (kW), kilojoules (kJ), and British Thermal Units (BTU). Here are easy steps to follow to get the cooling capacity required for your room:

  • Figure out the dimensions of the house or room you would like to cool (or heat). You can use a measuring tape if it is a room or consult the blueprints to get your home’s measurements.
    Get the number in square metres, which requires you to multiply the length and width of the room. Then, add the area for the total.
  • If you plan to cool more than one room with one split system, repeat the step above for each room.
  • The general formula is multiplying the room size by 150 watts to get the aircon size. The number of watts will depend on the ceiling height of the specific space. Since most homes in WA have 2.4-metre high ceilings, we follow the 150 watts rule. However, if your home’s ceiling is 2.7 metres high, multiply the room square metre by 160 watts. For three-metre-high ceilings, multiply by 175 watts.
  • The result represents the wattage estimate required to cool your room properly. Divide the wattage by 1,000 to convert the number into kilowatts.

So, if your room is 100 square metres and the ceiling height is 2.4 metres, you need 15,000 watts (100 sqm x 150 w). Divide 15,000 by 1000, and you get 15 kW.


Consulting Manufacturer’s Guidelines

Aside from measuring the room size to determine aircon cooling requirements, you should also look into the manufacturer’s guidelines. Air conditioners come in various sizes, and manufacturers typically tell you if their product is suitable for your room size and needs. Room length and width, along with ceiling height, have significant impacts on aircon efficiency. Knowing the floor space is important, but so is the total volume. So, don’t forget that high ceilings require more cooling power.

Other factors to consider include:

  • Insulation: If the ceilings and walls are insulated, your home is more thermally efficient than spaces without insulation. Also, determine what’s underneath and on top of the area, which can help avoid unnecessary strain on the aircon whilst maintaining temperatures consistently and dissipating heat properly.
  • Location: Your location tells you the appropriate aircon size for your home. WA is known for having the lowest amount of rainfall compared to other states. Therefore, most residents require more cooling power than those residing in Tasmania, for example.
  • Room Orientation: Where your rooms face is essential in finding the correct aircon size. The sun path in Australia is angled to the north, meaning north-facing windows deliver more radiant heat. West-facing windows capture the full glare of the sun, particularly in the afternoon. Therefore, your home requires more cooling compared to southern-facing houses, which are usually shaded and cooler.

When in doubt, always consult a professional who can calculate the correct aircon load based on your room size, manufacturer’s specifications, room requirements, and location. Air-Cond Installs WA will not only install your air conditioner for you but also help you assess and select the best type and aircon size for your home.

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