Heating and cooling
What is reverse-cycle air conditioning?
Reverse-cycle air conditioning is one of the most energy-efficient ways to heat and cool your home. It can replace separate heating and cooling appliances and help you move away from gas heating.
There are three main system options and the right system depends on which rooms you want to heat or cool, your home’s layout and insulation, and your electrical supply.
1. Split system
Best for: One room, such as a bedroom, or a living and dining area.
A split system has one indoor unit connected to one outdoor unit. It is generally a good choice when you want to condition specific rooms without heating or cooling the whole house.
- Bedrooms: Around 2.5 kW is a useful starting point.
- Living rooms: Often around 3.5–5 kW.
- Large living/dining areas: May need 5–8 kW or more.
These are indicative heating/cooling capacity ranges, not a substitute for proper sizing.
2. Multi-split system
Best for: Heating and cooling several rooms where you want to minimise the number of outdoor units.
One outdoor unit connects to multiple indoor units, allowing different rooms to be controlled separately. It can be a useful middle ground between installing separate split systems and choosing ducted air conditioning.
- Bedrooms: Around 2.5 kW per room may be suitable, depending on the room size.
- Living areas: Larger indoor units will be needed.
- The outdoor unit must be sized for the combined system and the manufacturer’s permitted combinations.
An aircon installer will be able to calculate the appropriately sized system for your house.
3. Ducted system
Best for: Heating and cooling multiple rooms or most of the home through ceiling or floor vents.
A central unit distributes conditioned air through ducts. Many systems offer zone control, allowing you to heat or cool selected areas rather than the entire house.
- The system needs to be sized for the home’s overall heating and cooling requirements.
- Duct design, insulation and sealing affect efficiency.
- Installation can be more expensive, particularly if ductwork or electrical upgrades are needed.
Ducted systems have substantial electrical requirements. Larger systems may need three-phase power or a switchboard upgrade. These systems often use more electricity overall because they condition a larger area and can lose energy through ductwork. Good design, zoning and insulation can reduce this.
What size air conditioner do I need?
These indicative ranges are a starting point for single-split and multi-split systems.
| Room size | Indicative cooling | Indicative heating |
|---|---|---|
| Up to 20 m² — bedroom or study | 2–2.5 kW | 2.5–3 kW |
| 21–40 m² — larger bedroom or small lounge | 2.5–5 kW | 3–5 kW |
| 41–60 m² — living room or large kitchen | 4–6 kW | 5–8 kW |
| Over 60 m² — large open-plan area | 5–9 kW | 8 kW+ |
Room size is only one factor. Insulation, ceiling height, window size, orientation, shading, draughts and connected spaces all affect the required capacity. Ducted systems need an assessment of the whole home.
What to look for when buying
Get the sizing right
Use the table above as a starting point, but ask the installer to assess your home’s layout, insulation, ceiling height, windows, shading and how you use each room. Ducted systems need an assessment of the whole home.
Is it better to install a larger unit?
Not necessarily. An oversized unit costs more upfront and may cycle on and off more frequently, affecting comfort and reducing energy efficiency. The aim is to choose the right capacity for the space, not simply to go bigger. (On the flip side, a system that is too small may struggle in extreme weather.)
Will I need a switchboard upgrade?
Not always. It depends on the air conditioner’s electrical requirements and your existing switchboard and power supply. Larger systems, particularly ducted systems, may need a dedicated circuit, three-phase power or a switchboard upgrade. Ask the installer to assess this before you commit to a quote.
How do I start?
- Decide which rooms to heat and cool.
- Measure your rooms.
- Check your home’s insulation and window orientation.
- Choose the type of system.
- Get an installer assessment and quote.
IWCE can help you understand the options, identify the key questions to ask and connect you with a trusted local installer. Contact us to get started today.