What is reverse cycle air conditioning?

How does reverse cycle air conditioning work?

Every air conditioner has two coils, a compressor and a refrigerant loop. One coil sits inside, one outside. The refrigerant absorbs heat where it evaporates and releases heat where it condenses. The compressor is the pump that keeps it moving.

In cooling mode the indoor coil is the cold one. It absorbs heat from the room and the outdoor unit throws it away outside. The federal YourHome guide describes it simply: in cooling mode the system absorbs heat from indoor air and releases it outside; in heating mode it absorbs heat from the outside air and distributes it around the room.

The part that makes it "reverse" is a reversing valve in the outdoor unit. When you press heat, the valve swaps the direction the refrigerant flows. The outdoor coil becomes the cold one, collecting heat from the outside air, even on a cold morning. The indoor coil becomes the hot one, and the indoor fan blows that heat into the room.

Cold outside air still holds plenty of heat for a heat pump to collect. That is the idea people find hardest to believe, and it is the reason the numbers below work.

Heat pump vs reverse cycle: what is the difference?

There is no difference. A reverse cycle air conditioner is an air-source heat pump. The Australian Government's YourHome guide says exactly that: a reverse cycle air conditioner is a type of heat pump that uses electricity to warm your home in winter and cool it in summer.

"Heat pump" is the international term and the one used in Europe and New Zealand. "Reverse cycle" is the Australian retail term. When a brochure says "heat pump split system", it means a reverse cycle split.

One thing to keep separate. A heat pump hot water system uses the same principle to heat a water tank. It is a different appliance, with its own rebates, and has nothing to do with your air conditioning.

How efficient is reverse cycle heating?

The energy.gov.au guidance puts reverse cycle air conditioners sold in Australia at 300% to 600% efficient. They can do that because they do not use electricity to make heat. They use it to move heat that is already outside.

The efficiency number for heating is called the coefficient of performance, or COP: the heat delivered divided by the electricity used. A COP of 4 means 4 kW of heat for 1 kW of electricity. Cooling has its own measure, the energy efficiency ratio, or EER. Both sit behind the star ratings on the Energy Rating label.

Does reverse cycle heating work in cold climates?

Yes, with two caveats. As the outdoor temperature drops, there is less heat to collect and the unit works harder, so heating output and efficiency fall. And on cold, damp mornings the outdoor coil can frost over. The unit then pauses heating for a few minutes to defrost it, which is normal and not a fault.

Both problems are about choosing the right model. For Canberra, Hobart, the Victorian and NSW highlands, or anywhere with frosty winters, do this.

• Read the heating star rating for the cold zone on the Zoned Energy Rating Label, not the cooling stars for the hot zone.
• Ask for the rated heating capacity, and how much of it the unit still delivers at low outdoor temperatures. Good cold-climate models publish this.
• Size for heating, not cooling. In a cold climate, heating is usually the bigger load.
• Mount the outdoor unit where defrost water can drain away and the unit is not buried in snow drift or leaf litter.

City detail is on the Canberra and Hobart pages. If you get up to three local quotes, mention the frost; a good installer will size for your winter, not the brochure.

What does reverse cycle heating cost to run?

At about 32c/kWh, a modern 3.5 kW reverse cycle split costs roughly 15c to 25c an hour once the room is warm. A 7.1 kW living-area unit is about 35c to 50c. Whole-home ducted reverse cycle runs about 70c to $1.10 an hour depending on how many zones are open.

The thermostat matters as much as the machine. energy.gov.au says each extra degree of heating adds 5% to 10% to energy use. Set 18 to 20 degrees in winter; more on that in the best temperature for your air conditioner. For your own tariff and hours, use the running cost calculator.

Against gas, reverse cycle usually wins on running cost at 2026 tariffs, which is why Victoria offers a Victorian Energy Upgrades discount for replacing gas ducted heating. The current rules are on the Victorian rebate page, and a local quote will show whether it applies to your house.

Types of reverse cycle air conditioner

More on each: what is a split system, split vs ducted and the systems overview. Prices by size are in the split system cost guide and the ducted cost guide. For your own number, get up to three local quotes.

Reverse cycle vs split system vs refrigerated

These words get used as if they compete. They do not. "Split system" is a layout. "Reverse cycle" is a capability. "Refrigerated" is the Perth and Adelaide word for any air conditioner that uses a refrigerant loop, to tell it apart from evaporative cooling.

So a reverse cycle split system is a refrigerated air conditioner, in the split layout, that heats. If a quote says "refrigerated" or "split" and does not say "reverse cycle", ask whether it heats. The comparison with evaporative is in reverse cycle vs evaporative.