Information to help you choose the right size reverse cycle air conditioner for your household.
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onThink carefully about what your household needs from a new reverse cycle air conditioning system. Every household is unique, and this impacts what size is appropriate.
What is an efficient reverse cycle air conditioner and why should I install one?
Space heating and cooling accounts for over 50% of residential energy use in Victoria. Upgrading to an efficient heating and cooling system is a great way for households to save on energy bills and reduce greenhouse gas emissions.
The Victorian Energy Upgrades (VEU) program offers incentives for households to upgrade to efficient reverse cycle air conditioners, which can heat and cool your home. Only products meeting VEU program requirements can be installed under this program. There are 3 types of reverse cycle air conditioners offered under the VEU program. These include:
Single-split – one outdoor unit connected to one indoor unit, suitable for heating or cooling a single room or open-plan area.
Multi-split – one outdoor unit connected to multiple indoor units, suitable for heating or cooling multiple rooms or whole-of-home.
Ducted – one central outdoor unit connected to multiple indoor rooms through ducts and vents, suitable for heating or cooling your whole home.
There is a range of reverse cycle air conditioners eligible under the VEU program.
Remember to do your research on the products you intend to buy:
Not all products are of the same quality or suitability for all households.
Products can have different features that may be better suited to your household.
Using a trusted installer and buying a reputable brand and model will reduce the likelihood of problems down the track.
The performance and energy efficiency of reverse cycle air conditioners also varies between products. Choosing a more efficient system will deliver greater savings on household energy bills.
It’s also important to consider warranty when installing a new reverse cycle air conditioner:
Warranties offered vary from one manufacturer to another.
Remember to read the warranty conditions carefully and note that some warranties are conditional on installation by appropriately qualified personnel.
Always speak to your installer about product and installation warranty.
Energy rating labels
Reverse cycle air conditioners display a zoned energy rating label. The label provides information on energy consumption of the product based on the climate it is installed. Products are star rated for both heating and cooling. The more stars a product has, the less energy it will use.
Find further information about the energy rating of each product on the Australian Government's Energy Rating website.
Choosing the right size reverse cycle air conditioner
The size of an air conditioner refers to its rated heating and cooling capacity output. Products should list size in kilowatts (kW), for example, 3.5 kW. Reverse cycle air conditioners have both a heating and cooling size and these can be different.
Think carefully about what your household needs from a new air conditioning system:
A system that is too small may not be able to properly heat or cool your home on the coldest/hottest days and will take longer to bring the room to a comfortable temperature.
A system that is too large will cost more to buy and may cost more to run. Larger systems tend to be less efficient than smaller systems. Systems that are oversized can also result in large temperature swings, reducing occupant comfort.
Every household is unique, and this impacts what size is appropriate.
Important considerations before choosing your new system
Before investing in a new heating and cooling system, it is important to consider the efficiency of your home. An efficient home will be easier and cheaper to heat and cool throughout the year.
Are there draughts in your home?
Look for gaps around windows, doors and vents that allow hot and cool air to escape.
These gaps can increase your heating and cooling costs.
It is recommended to seal these gaps to help control the temperature of your home and lower your heating and cooling needs.
Are your roof, walls and floors correctly insulated?
The level of insulation in your house directly impacts the level of heating and cooling you may require.
Heat is lost through walls, floors and ceilings during the winter increasing your heating requirements.
During summer, heat is gained the same way, increasing your cooling requirements.
Consider the level of insulation in your home when considering your heating requirements.
How is your home constructed? For example brick or weatherboard?
The construction material of your house can impact your heating and cooling requirements.
It is an important aspect to consider when sizing your reverse cycle air conditioner.
What are your local climate conditions?
The amount of energy you need to heat and cool your house depends on your local climate.
Victorians typically use more energy for heating than cooling, so look for a unit with a higher heating efficiency.
The zoned energy rating label on your product is designed to compare the energy efficiency of similar sized appliances in your local climate.
Speak to your installer about models and sizes best suited to the climate of your location.
How much sun or shade does your house receive?
The direction your house faces can impact the amount of natural heat gained that can lower your heating load during the day.
Does your room have numerous large, single glazed windows? These can be a main source of heat loss during winter or heat gain during summer.
The area of the room/s you would like to heat and cool is an important factor.
Area is not only length by width but ceiling height too.
Ceilings higher than the room standard of 2.4 m will require more energy to heat and cool.
Consider the air flow of your house especially if the system installed is to service multiple rooms.
When considering a new reverse cycle air conditioner, discuss the rooms you want heated and cooled with your installer. Ask yourself the following questions:
What rooms do you use the most?
What are the hottest and coldest rooms in your home?
How do you use your current heating and cooling? for example do you want to include bedrooms?
If you already have heating or cooling, would you change its coverage?
We recommend that your new system covers your primary living spaces such as:
living rooms
family rooms
lounges and open plan living areas.
Also consider what rooms are covered by your existing heating or cooling:
Covering too many rooms will increase the cost to buy and run your system. Covering too few rooms may result in your heating and cooling needs not being met.
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)
Bedroom, study
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
+8 kW
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.
Zones
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.
Ducting
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.
Other considerations when planning a reverse cycle air conditioner
Noise and system placement
Speak to your installer about noise and system placement.
Both indoor and outdoor components of reverse cycle air conditioners make noise.
Noise complaints are commonly associated with noise from reverse cycle air conditioners. Consider the impact of noise on your household and neighbours.
The Zone Energy Rating label has noise indicators at the bottom to show the volume in decibels (dB(A)) of the air conditioner.
Outdoor components require good air circulation to work efficiently. Lack of air flow can lower the output of your unit, using more energy to work at a standard level.
Switchboard
Consider if your switchboard requires an upgrade to accommodate your new system.
Speak to your installer about switchboard suitability and requirements.
Solar
All VEU reverse cycle air conditioners are electric and can make use of electricity generated from a solar PV system.
Find further information at Solar Victoria, to see how a solar system can maximise your energy savings when heating or cooling your house.
