What is Reverse Cycle Air Conditioning
With nearly half the households across Australia installing reverse cycle air-cons, the answer is quite straightforward: it's only the most popular air conditioning system in the country.
It keeps your home warm in winter and cool in summer, and it’s more efficient than standard systems, too.
Below, we’ll go over how a reverse cycle air conditioner works, the benefits of using one, and how to manage it after installation. We’ll also walk you through different system types and help you choose the right reverse cycle air conditioner for your space.
Table of Contents
What Is Reverse Cycle Air Conditioning and How Does It Work?
A standard cooling-only air conditioner moves heat from indoor air and dumps it outside.
A reverse cycle air conditioner uses the same process to cool indoor air but also contains a valve that reverses or flips the refrigeration cycle, such that instead of only absorbing heat from indoor air and moving it outside, the air-con absorbs heat from outdoor air and moves it inside as well.
American engineer Robert C. Webber pioneered this dual-function system in 1948. By the 1990s, it was the system of choice for most Australians.
What Are the Components of a Reverse Cycle System?
Five main components work together to enable reverse cycle operation. Let’s take a quick look at them.
- The compressor sits in the outdoor unit and pumps refrigerant through the system while increasing its pressure and temperature.
- The evaporator coil in your indoor unit draws in air and aids heat absorption as refrigerant transforms from liquid to gas.
- The condenser coil expels heat and cools the refrigerant back into liquid form.
- An expansion valve controls refrigerant flow and reduces pressure and temperature before it re-enters the evaporator.
- The reversing valve sits near the compressor and allows the system to switch between heating and cooling modes by changing the refrigerant’s direction.
The Refrigeration Cycle Explained
- The process starts when refrigerant enters the evaporator as a low-pressure liquid and absorbs heat energy from indoor air. It transforms into a gas.
- The compressor then pressurises this gaseous refrigerant and raises its temperature substantially.
- This hot, high-pressure gas flows to the condenser, where a fan blows air across the coil.
- The refrigerant releases heat and condenses back into liquid form.
- The expansion valve drops the refrigerant’s pressure and temperature before it returns to the evaporator to restart the cycle.
What Makes It “Reverse Cycle”?
Two words: reversing valve
The reversing valve is what differentiates a reverse cycle air conditioner from a standard air conditioner.
This valve contains a slide mechanism (a small moving part that shifts position inside the valve) and a solenoid coil (an electrically activated switch that controls that movement).
When you switch between heating and cooling modes using your remote or wall controller, the thermostat sends an electrical signal to the solenoid.
On receiving that signal, the solenoid moves the internal slide and redirects the flow of refrigerant through the system. As a result of that redirection, the compressor pressurises the refrigerant gas, which raises its temperature.
In cooling mode, this hot, high-pressure refrigerant flows to the outdoor coil where the heat is released outside.
In heating mode, the solenoid reverses the flow and sends the hot refrigerant to the indoor coil instead, warming your home.
Benefits of Reverse Cycle Systems for Australian Homes
Enjoy consistent comfort every season.
Cool your space when temperatures soar to 46°C and warm it when conditions drop below freezing. With a reverse cycle air conditioner, you won’t need to install a heater. One system gets the job done.
“Energy efficiency” asks one question: How much useful heating or cooling do you get from each unit of electricity?
The more energy-efficient a system is, the more heating or cooling it delivers per kilowatt of electricity consumed.
The Department of Climate Change, Energy, Environment, and Water has confirmed that reverse cycle ACs are 300% to 600% efficient. That means they use three to six times less electricity than a conventional electric heater to produce the same amount of warmth.
When outdoor temperatures are mild (15–25°C), a reverse cycle system can be up to 1000% energy-efficient, outputting as high as 10 kW of heating/cooling for each kW of electricity drawn.
For you, that means smaller power bills and higher cost savings over time.
Modern reverse cycle air conditioners come with air filters that trap dust from indoor air.
If you have asthma or allergies, look for products approved by the Sensitive Choice programme; they’re typically fitted with purification filters that eliminate mould spores, allergens, fine dust, and pet hair and dander.
Panasonic’s nanoe-G purification system, for example, is said to deactivate over 99% of airborne bacteria, viruses, and mould that rest on surfaces or come in contact with the filter.
It also has a built-in humidifier that balances moisture levels within the home, preventing air dryness and reducing throat irritation.
Heating and cooling produces greenhouse gas emissions because it uses electricity, and electricity generation still partly relies on fossil fuels. A reverse cycle air conditioning system consumes less electricity to do this job and lowers the volume of emissions.
Each reverse cycle AC installed brings Australia a step closer to reaching her national target of net zero emissions by 2050.
Types of Reverse Cycle Air Conditioners
A single split system comprises just one outdoor unit and one indoor unit. It’s the most common type in Australian homes and suits individual rooms or open-plan areas up to about 60 square metres.
Because each system serves one room or space in the home, you would need separate systems for each room, each with its own outdoor unit.
A multi-split system connects one outdoor unit to multiple indoor units, typically up to five.
Each indoor unit operates independently, so you can set different temperatures in different rooms. An advantage is you won’t have to install as many outdoor units on your property.
In a ducted system, there’s a single central indoor unit that services all rooms within the home and a single outdoor unit that completes the heat transfer cycle.
The indoor unit is usually installed in the ceiling space and distributes conditioned air through ductwork and vents in each room.
You can control which rooms receive conditioned air and at what temperature. Ducted systems are less efficient than split systems due to heat loss through the ductwork, and they require more complex installation.
Technically, portable reverse cycle units are self-contained.
They aren’t split into indoor and outdoor units, and they don’t require permanent installation. Instead of an outdoor unit and refrigerant conduction pipes, they use a flexible hose fed outside through a window to vent hot air.
While they may be a bit noisier and less efficient than split-system options, they’re a solid option for renters or anyone who cannot install a fixed system.
Choosing the Right Reverse Cycle Air Conditioner for Your Needs
In the table below, we compare the various types of reverse cycle air conditioning systems. As you read through, you'll gain a clearer idea of which direction to take.
| Feature | Single-Split | Multi-Split | Ducted | Portable |
| Rooms served | 1 | 2–5 | Whole home | 1 (small) |
| Best for | Apartments, single rooms, home offices, open-plan living areas | Mid-sized homes, apartments with limited outdoor space, homes with complex layouts or extensions | Large family homes, new builds, renovations with ceiling space available | Renters, temporary setups, rooms where permanent installation is not possible |
| Outdoor units | 1 per room | 1 for all indoor units | 1 | None (vents through window hose) |
| Visibility | Indoor unit visible on wall or floor | Indoor units visible in each room | Only ceiling vents visible | Freestanding unit visible in room |
| Independent room control | Yes (each unit is self-contained) | Yes (each indoor unit has its own settings) | Yes, with zoning | No |
| Installation complexity | Low | Moderate | High | None |
| Efficiency | Highest | High | Lower due to heat loss through ductwork | Lowest |
| Noise (indoors) | Low | Low | Lowest (central unit hidden in ceiling) | Highest |
| Strata/body corporate approval | May be required for outdoor unit | May be required | May be required | Not required |
| Suits renters | Generally no (permanent install) | No | No | Yes |
Factors to Consider When Making Your Decision
Prioritise these considerations when selecting a reverse cycle air conditioning system.
- Room dimensions and ceiling height: A large room with a high ceiling has more air volume than a small space with a lower ceiling. A unit sized for a standard 2.4-metre ceiling will underperform in a room with 3-metre ceilings because there is more air volume to condition.
- Insulation quality: Insulation helps a home retain conditioned air more effectively, thus reducing how much work the air con has to do. For example, adding ceiling insulation to a 30-square-metre room can reduce the required capacity from 2.9 kW to 2.3 kW.
- Window orientation and glazing: North-facing windows admit more heat than south-facing windows. Large or single-glazed windows increase the cooling load in summer and the heating load in winter.
- Climate zone: Where you live in Australia directly affects how hard your system has to work. A 30-square-metre room in Darwin may require 2.9 kW of cooling capacity per hour, while the same room in Hobart may only need 1.8 kW.
- Energy star ratings: More stars mean the unit uses less electricity to deliver the same output. First determine the right capacity for your space, then compare star ratings among similarly sized models.
Once you have a sense of what your space requires, reach out to a licensed installer for a heat load calculation to determine the exact capacity you need. When doing their calculations, they’ll take into account all the factors above and arrive at an optimal kilowatt figure.
Getting a professional heat load calculation helps avoid a situation where the unit’s capacity is too big or small for your space.
An undersized unit will run constantly trying to reach your set temperature, wasting electricity and wearing out faster. An oversized unit reaches the set temperature too quickly, shuts off, then restarts shortly after, repeating this cycle throughout the day.
This stop-start pattern prevents the system from properly removing moisture from the air, leaving the room feeling cold but clammy.
Making the Switch to Reverse Cycle Air Conditioning
The best way to size your reverse cycle air conditioner involves having your installer conduct an onsite load assessment and calculation.
Also ensure licensed professionals handle all installation work, as installing a unit yourself without a valid licence or contracting unlicensed installers is illegal in Australia.
If you live in Brisbane or on the Gold Coast and are considering installing a reverse cycle air conditioning system in your home, get in touch.
We’re qualified electricians with more than 15 years of experience installing air conditioners in residential homes and are fully licensed by the Australian Refrigeration Council and the Queensland Building and Construction Commission.
Fill out our contact form and we’ll get back to you with a free quote.