Is a reverse cycle air conditioner a heat pump? Yes — and it explains your entire power bill.
Australia uses two words for one machine, and the confusion costs people money. A reverse cycle air conditioner is a heat pump: it doesn't make heat, it moves it, which is why one unit of electricity buys you three to five units of warmth. An electric panel heater can never beat one, because physics won't allow it. Here's how it actually works, where the efficiency goes, and how to tell whether the unit on your wall can even heat.
Reviewed by the Mission Green Energy Team · Updated August 2026
Is a reverse cycle air conditioner
a heat pump?
Yes. Same machine, same physics, different marketing word.
A reverse cycle air conditioner is a heat pump. Not similar to one, not based on one — it is one. The two terms describe the same device, and the reason Australia uses two words for one machine is historical and commercial, not technical.
Here is the useful bit. A resistive electric heater — a fan heater, an oil column, a panel heater, the element in an old hot water tank — makes heat by pushing electricity through a resistance. One kilowatt-hour of electricity in, one kilowatt-hour of heat out. That is the ceiling: it can never be more than 100% efficient, because you cannot get more energy out than you put in.
A heat pump doesn't make heat. It moves heat — collecting it from the outside air and carrying it indoors using a refrigerant circuit and a compressor. Because moving heat takes far less energy than creating it, one kilowatt-hour of electricity typically delivers three to five kilowatt-hours of warmth. That ratio is the Coefficient of Performance, or COP, and modern units in Australian conditions generally sit around a seasonal COP of roughly 3 to 4.5 depending on climate.
That is the whole reason reverse cycle is the cheapest way to heat a room in every Australian state. Not a better element — a completely different physical principle.
So why does Australia
use two different words?
Because we bought the machines for cooling first, and the language stuck.
Australia adopted these units as air conditioners — things you buy to survive summer. Heating was the bonus feature, the “reverse” mode, so the industry sold it as a reverse cycle air conditioner: an air conditioner that can run its cycle backwards. Flip a valve, and the machine that was pumping heat out of your house pumps heat into it instead. Literally the same components running in the opposite direction.
Meanwhile, when the same technology was applied to water heating and to cold-climate home heating, it was marketed as a heat pump — because there was no air-conditioning heritage to trade on. So today an Australian household can end up with a “heat pump hot water system” in the yard and a “reverse cycle air conditioner” on the wall, both doing the same thing to different substances, and reasonably assume they are unrelated technologies.
They are not. And knowing that is genuinely useful, because it means everything you learn about one applies to the other: both are dramatically cheaper to run than resistive alternatives, both perform less efficiently as the outside air gets colder, both benefit enormously from running while your solar is generating, and both are sized and installed rather than simply plugged in.
| What it's called | What it heats | Is it a heat pump? |
|---|---|---|
| Reverse cycle air conditioner / split system | Room air | Yes — an air-to-air heat pump |
| Ducted reverse cycle | Air, distributed through ducts | Yes — the same thing, centrally ducted |
| Heat pump hot water system | Water in a storage tank | Yes — an air-to-water heat pump |
| Hydronic heat pump | Water for radiators or slab heating | Yes — air-to-water, for hydronic circuits |
| Cooling-only split system | Nothing — cools only | It's the same hardware without the reversing valve, so it can only pump heat outwards |
| Electric panel / fan / oil column heater | Room air | No — resistive. Makes heat rather than moving it, so ~1 unit in, 1 unit out |
Are all air conditioners
reverse cycle?
No — and it's worth checking before you assume yours can heat.
Not all of them. Cooling-only split systems are still sold in Australia, usually at a lower purchase price, and they are common in warm-climate installs and in budget fit-outs. Mechanically they are nearly identical to a reverse cycle unit — the difference is a four-way reversing valve that lets the refrigerant flow the other way. Without it, the machine can only move heat out of the house.
Three ways to tell what you have:
- Check the remote. A sun or flame icon, or a “Heat” mode, means reverse cycle. If the modes are only Cool, Dry, Fan and Auto, it is very likely cooling-only.
- Check the nameplate on the indoor or outdoor unit. If it lists a heating capacity in kW as well as a cooling capacity, it heats.
- Check the energy label. Australian air conditioners carry a Zoned Energy Rating Label; a reverse cycle unit shows both heating and cooling star ratings across hot, average and cold zones.
If you are buying, the price gap between cooling-only and reverse cycle is usually small relative to what you would otherwise spend heating the same room with a resistive heater over a single winter. In most of Australia, choosing cooling-only to save a little upfront is a false economy — it is the classic case of a cheaper purchase costing more to own.
Where the efficiency
actually goes.
A heat pump is not magic, and three things genuinely reduce its advantage.
Cold outside air
The colder it is outside, the less heat there is to collect, so COP falls as the temperature drops. Modern units still work well below zero — ACT Climate Choices notes good reverse cycle systems work even at −10°C — but if you're in Ballarat, Canberra, Hobart or the highlands, insist on a cold-climate H2-rated unit and don't buy on the cooling star rating alone.
The defrost cycle
In cold, damp conditions frost forms on the outdoor coil and the unit periodically reverses briefly to melt it. During defrost it isn't heating your room, and it draws power to do it. This is normal operation, not a fault — but it does eat into real-world seasonal efficiency, which is why the seasonal COP is always lower than the headline lab figure.
Sizing and installation
An oversized unit short-cycles and never settles into its efficient inverter range; an undersized one runs flat out and never gets there either. Poor installation — an outdoor unit crammed against a wall, an incorrect refrigerant charge, ductwork that leaks into the roof space — can quietly cost more efficiency than any spec-sheet difference between brands.
Why this changes
how you should run it.
Once you know it's a heat pump, three habits follow naturally.
Run it during the day if you have solar. A heat pump multiplies whatever electricity you feed it, so feeding it free solar rather than paid grid power multiplies the saving too. Pre-warming the house in the middle of the day and letting it coast into the evening is usually cheaper than heating hard at 6pm on peak rates — and if you're on a free-window plan, our guide to the Solar Sharer free power window covers how that interacts.
Set a sensible thermostat and leave it. Because an inverter heat pump is most efficient when it settles into a steady low output, constantly cranking the setpoint up and down is worse than picking a temperature and letting it hold. Every degree costs, so 20–21°C in winter rather than 24°C is one of the cheapest savings available.
Fix the building before you fix the machine. A heat pump's job is replacing heat that escapes. Draught-proofing gaps, closing off unused rooms and covering windows at night reduce how much heat escapes in the first place, and none of that costs an ongoing kilowatt-hour. It is genuinely the cheapest energy you will ever save.
And if the same logic appeals for your hot water — which is typically a bigger share of a household's energy than space heating — a heat pump hot water system applies the identical principle to your tank. Just be careful with the “free” heat pump offers doing the rounds.
Is a reverse cycle air conditioner a heat pump?:
your questions, answered.
Yes. They are the same device described with two different words. A reverse cycle air conditioner is an air-to-air heat pump: it uses a refrigerant circuit and a compressor to move heat from outside your home to inside it, rather than generating heat directly. The term heat pump is generally used in Australia for hot water systems and hydronic heating, while reverse cycle is used for air conditioners, but the underlying technology is identical. This matters practically because a heat pump moves heat instead of making it, so one unit of electricity typically delivers three to five units of warmth, whereas a resistive electric heater can never deliver more than one. That efficiency ratio is why reverse cycle is the cheapest way to heat a room in every Australian state.
No. Cooling-only split systems are still sold in Australia, usually at a lower purchase price. Mechanically they are almost identical to a reverse cycle unit — the difference is a four-way reversing valve that allows the refrigerant flow to be reversed, so the machine can pump heat inwards as well as outwards. To check what you have, look for a heat mode or a sun or flame icon on the remote, look for a heating capacity in kW on the unit nameplate, or check the Zoned Energy Rating Label, which shows both heating and cooling star ratings for reverse cycle models. If you are buying new, the extra cost of reverse cycle over cooling-only is usually small compared with what you would spend heating the same room with a resistive heater over one winter.
It moves heat rather than creating it. A refrigerant circulates between an indoor coil and an outdoor coil, driven by a compressor. In cooling mode the indoor coil absorbs heat from your room air, the refrigerant carries it outside, and the outdoor coil releases it. In heating mode a reversing valve sends the refrigerant the other way: the outdoor coil now absorbs heat from the outside air — there is usable heat in air even at low temperatures — and the indoor coil releases it into your room. Because the machine is transporting existing heat rather than generating it, it delivers far more heat energy than the electrical energy it consumes. That ratio is called the Coefficient of Performance, and modern units in Australian conditions typically achieve a seasonal COP of roughly 3 to 4.5, meaning three to four and a half units of warmth per unit of electricity.
Yes, though efficiency falls as the outside temperature drops, because there is less heat in the air to collect. Modern units still heat effectively well below zero — ACT Climate Choices states that good reverse cycle systems work even at minus 10 degrees Celsius. The practical advice for cold parts of Australia such as Canberra, Ballarat, Hobart and the highlands is to choose a cold-climate rated unit, ask specifically whether it carries an H2 rating, and read the cold-zone heating star rating on the Zoned Energy Rating Label rather than the average or cooling rating. You should also expect the unit to run a defrost cycle periodically in cold damp conditions, briefly reversing to melt frost off the outdoor coil. That is normal operation rather than a fault, though it does reduce real-world seasonal efficiency below the headline laboratory figure.
In cooling mode, yes — unavoidably. When warm room air passes over the cold evaporator coil, moisture condenses out of it, which is exactly why your indoor unit produces water and needs a condensate drain. That dehumidifying effect is a by-product of cooling rather than a separate function. Most units also have a dedicated dry mode, which runs the compressor gently with reduced fan speed specifically to pull moisture out without over-cooling the room, useful on humid but mild days. In heating mode the effect reverses in practical terms: the unit is not condensing moisture out of your room air, and heated air feels drier because warmer air can hold more moisture at the same absolute humidity. If a room feels uncomfortably dry in winter, that is the physics of heating rather than a fault in the machine.
Yes, applied to water instead of air. A heat pump hot water system is an air-to-water heat pump: it collects heat from the surrounding air and uses it to heat the water in a storage tank, using the same refrigerant-and-compressor principle as the reverse cycle unit on your wall. That is why it uses roughly a third to a quarter of the electricity of an old resistive electric element tank for the same hot water. The same limits apply too — efficiency falls in colder ambient conditions, sizing and installation quality matter, and it performs best when run during the day, ideally on your own solar generation. Because hot water is often a larger share of a household energy bill than space heating, switching a resistive element tank to a heat pump is frequently a bigger saving than anything you do to your heating.
Where these figures come from.
Figures on this page are drawn from primary sources and were current as at August 2026. Programs, prices and standards change — confirm at the source before relying on a number.
- Energy Rating — Air conditioners and the Zoned Energy Rating Label (energyrating.gov.au)
- energy.gov.au — Heating and cooling for Australian households
- ACT Everyday Climate Choices — reverse cycle performance in cold climates (climatechoices.act.gov.au)
- Your Home — Australia's guide to environmentally sustainable homes: heating and cooling (yourhome.gov.au)
- energy.gov.au — Hot water systems, including heat pump hot water