Calculate your heating and cooling requirements
The best way to correctly size your reverse cycle air conditioner is for your installer to conduct an onsite load assessment and calculation. This will allow your installer to consider your individual heating and cooling needs based on your home.
There are online calculators to assist with estimating your heating and cooling load, including the FairAir calculator, developed by the Australian Institute of Refrigeration, Air Conditioning and Heating (AIRAH).
You will need to know:
- the region (climate area) that the room is located in
- the dimensions of the room to be heated: length (m), width (m), height (m)
- the total area (m²) of ceiling, floor, external walls, external glazing (windows and doors) and internal walls (separating walls/doors) to other rooms or areas that are not included in the heated room
- the type of construction of the main building elements: roof/ceiling, floor, glazed windows and doors, internal and external walls, including whether they have been insulated or not.
Online calculators are estimates only and should only be used as a guide. Always speak to a heating and cooling specialist to fully understand the individual requirements of your household. Individuals with load estimation experience are best placed to provide the most accurate estimate.
Recommended size for your air conditioner
Disclaimer: Sizing any heating and cooling system involves taking into consideration various factors and not only the room size in square meters. We recommend that you consider the individual characteristics of your home prior to upgrade.
An important factor to consider when sizing your new system is the size of the space you want to heat or cool.
The table below provides a guide to the reverse cycle air conditioner size you'll need for a particular room size.
Recommended size for single-split or multi-split air conditioning
| Room size|| Example room|| Recommended heating output|
Small (up to 20 m²)
2.5 to 3 kW
Medium (21-40 m²)
Bedroom with ensuite, small lounge
3 to 5 kW
Large (41-60 m²)
Lounge, large kitchen
5 to 8 kW
Very large (more than 60 m²)
Open plan areas, large lounges
Recommended size for your ducted air conditioner
Ducted systems offer an effective way to heat and cool your entire home, however they can be more expensive to install and run due to heating and cooling a larger area. Hot and cool air lost through ducts can also increase running costs.
If you choose a ducted system, the right size can depend on several factors and should be discussed with your installer.
We recommend providing 1.1 to 1.4kW of heating output for every 10m² of your home covered by a ducted system depending on the individual characteristics of your home.
We recommend zones for your ducted system, as they allow more control over which areas of your home to heat and cool (for example, daytime living areas or bedrooms). Creating zones in your home is a more efficient option for ducted heating and cooling, allowing you to heat each zone individually rather than the whole home at once.
Speak to your installer to ensure your ducting is appropriately insulated and correctly sized for your heating and cooling load. Ducts can lose heat if they are not well sealed and insulated. Well-designed ducting will make your system more efficient to run.
If you are planning to install a ducted reverse cycle air conditioner, your existing ducting may need to be upgraded.
Older ducting may not be efficient or in good condition. The general rule of thumb is to replace your ducting especially when moving from gas to a reverse cycle air conditioner.