Air Conditioner Buyer’s Guide

A split system includes one indoor unit and one outdoor unit connected via refrigerant piping.

✔ Ideal for single rooms or open-plan areas up to 60m²

✔ Most common residential air conditioning system in Australia

✔ Efficient reverse-cycle heating and cooling

One outdoor unit connected to multiple indoor units.

✔ Ideal for 2–3 rooms

✔ Saves outdoor space

✔ Suitable when ducted isn’t practical

✔ Similar price range to separate split systems

Contact us for a free quote if you’re considering multi-split.

A central system installed in the roof cavity with ducts distributing air throughout the home.

✔ Whole-home heating & cooling

✔ Discreet ceiling vents

✔ Zoning options available

✔ Ideal for larger homes

Contact our team for a tailored ducted system quote.

Here’s our rough guide to the air conditioner capacity (size) you’ll need for a particular room size. 

Read the full article ‘What size air conditioner do I need?‘

Room SizeCapacity

Up to 20m2 - 2-2.5kW

20–40 m2 - 2.5–5kW

40–60 m - 4–6kW

60–80 m2 - 5–7kW

80+ m2 - 6–9kW

So, that’s the ballpark guide, but you really need to do an accurate calculation before buying your air con, or else you’ll run into these issues:

• Models too powerful for the room size may run frequent short cycles to achieve the target temperature. This can result in the room getting too cold or hot, inadequate dehumidification (i.e. not drying the air enough, making the room feel less comfortable), increased power consumption and running costs, and wear and tear on the system.
• Underpowered models may have to run more often at maximum output, which could dry the air too much and also create excessive wear.

Why the Right Size Matters
While many basic calculators suggest oversized units, choosing the right capacity requires a more nuanced approach. Factors such as insulation quality and window orientation play a critical role; for instance, an uninsulated room with west-facing windows demands significantly more cooling power than a well-insulated, south-facing space.

Furthermore, local climate matters: a home in Perth typically requires a higher-capacity system than an identical room in Sydney to achieve the same level of comfort.

At AC Hub we believe in precision. A truly efficient calculation goes beyond just floor space; it considers the unique DNA of your room.

Key Factors We Consider:

• Total Volume: We look at length, width, and especially ceiling height.
• Room Purpose: A kitchen with heat-generating appliances requires different cooling than a quiet bedroom.
• Glass & Orientation: Large west-facing windows act like heaters in summer, whereas south-facing glass stays much cooler.
• Thermal Barriers: The quality of your insulation and window coverings (like blackout curtains or shading) significantly impacts the load.
• Local Climate: A 20sqm room in the humid heat of Perth demands more "muscle" than the same room in Sydney’s temperate climate.

Running costs for a medium-sized air conditioner ranges from around $400–$550 a year. 

We measure running costs in our air conditioner reviews. As you can see in the below table, running costs can vary by a few hundred dollars a year, depending on the model.

Running costs of air conditioners, we tested:

• Small (up to 4kW) $242–$492
• Medium (4–6kW) $402–$552
• Large (over 6kW) $442–$586

Based on how much each model costs to deliver a set amount of cooling and heating per year at maximum capacity, with the remainder of the year in standby mode (based on electricity costs of 30 cents/kWh). It’s only indicative; your actual running costs may vary.

Maximising Efficiency: The 8°C Rule
To keep your system running at peak performance, we recommend maintaining a maximum temperature differential of 8°C compared to the outdoors.

• Summer Strategy: If it is 33°C outside, aim for an indoor setting of 25°C. While 20°C is tempting, every degree lower can increase your running costs by approximately 10%.
• Winter Strategy: In reverse-cycle mode, aim for no more than 8°C above the ambient outdoor temperature.

Adhering to this "8°C Gap" reduces mechanical wear on the compressor and significantly lowers your seasonal energy bills.

Read more: Air conditioner energy saving tips

Inverter systems adjust compressor speed rather than constantly turning on and off. This results in:

✔ Lower energy consumption

✔ Quieter operation

✔ Better temperature stability

✔ Reduced long-term wear

Modern split systems are generally very quiet.

Typical noise ranges:

• Indoor units: 19dB – 53dB
  
• Outdoor units: 42dB – 69dB
  

For comparison:

• 30dB = Quiet home
  
• 50dB = Quiet car interior
  
• 60dB = Normal conversation
  
• 70–80dB = Vacuum cleaner
  

Always check noise ratings if installing near bedrooms or neighbouring properties.