The Best Refrigerants For Hot Water Heat Pumps & Aircons

Refrigerants are the invisible workhorses of modern climate control. They play a critical role in the operation of both heat pump hot water (HPHW) units and air conditioning (AC) systems. These specialised chemical compounds cycle continuously to absorb heat from one area and release it into another, and are a large reason why split systems and heat pump hot water units are so efficient and cheap to run.

Why Does Refrigerant Choice Matter?

The evolution of refrigerants is a story of technological advancement. Driven by an increasing awareness of environmental impact, the market has shifted from highly damaging compounds to today’s low-Global Warming Potential (GWP) alternatives.

In this article I’ll explain how they work, which refrigerants are available in Australia, and what types are best when shopping for a new hot water heat pump or air conditioner.

Refrigerants Aren’t Just For Cooling

The word “refrigerant” is derived from the Latin verb refrigerare, which means “to make cool or cold” or “to cool again”. But refrigerants can heat just as well as they can cool.

The fundamental principle of refrigeration – whether cooling a room or heating water – is based on the simple thermodynamic principle that a fluid absorbs heat when it evaporates and releases heat when it condenses. The refrigerant is the medium that makes this heat transfer possible by repeatedly changing its state:

Evaporation (The Cooling/Heating Step): The refrigerant, in a low-pressure liquid state, enters a heat exchanger (the evaporator). For a HPHW unit, this is typically the unit’s outdoor coil, where it absorbs heat from the ambient outdoor air.

Compression: The low-pressure gas is then drawn into a compressor which pressurises the gas and, critically, raises its temperature far above the temperature of the water it will be heating. This is the energy-intensive part of the cycle.

Condensation (Heat Release): The now-hot, high-pressure gas moves to a second heat exchanger (the condenser). In an HPHW unit, it releases heat into the water tank, heating the water.

Expansion: Finally, the high-pressure liquid passes through an expansion valve, causing it to suddenly drop in pressure rapidly and cool into a liquid, ready to start the process again.

There are two key takeaways worth knowing about the role of the refrigerant.

The refrigerant acts as a thermal shuttle, efficiently moving heat from point A to point B.

This process is super efficient – and why we love HPHWs and split systems. For every one unit of energy it takes to run a heat pump, often we get 3, 4 or even 5 units of energy out. This is why HPHWs and split systems are so cheap compared to gas equivalents.

What Refrigerants Are Available In Australia?

The refrigerant industry has undergone a major shift over the years, transitioning from compounds that damage the ozone layer to alternatives that minimise global warming. In Australia, the shift is highly regulated under the Ozone Protection and Synthetic Greenhouse Gas Management Act. The focus is on replacing high-Global Warming Potential (GWP) gases with low-GWP alternatives.

Air Conditioning: The industry standard has largely transitioned from R-410A to R-32. R-32 is more efficient and, critically, has a GWP that is about one-third of R-410A, making it a better environmental choice while maintaining performance in split and ducted systems. With a still high GWP of 675, we expect the market for AC refrigerants to continue to develop.

Heat Pump Hot Water: The Australian HPHW market is heavily weighted towards ultra-low GWP refrigerants. R-290 (Propane) is currently the most common choice due to its excellent performance, affordability, and GWP of just 3. R-744 (Carbon Dioxide) is also used, particularly in premium units known for exceptional performance.

A Bad Refrigerant Means A Bad Product

I find there is a clear correlation between the quality of the refrigerant used in a heat pump and the quality of the product. It’s no coincidence that poorer-quality HPHWs and air conditioners use/used poorer quality refrigerants (and probably other poor quality inputs in the manufacturing process).

The following should be considered when analysing refrigerants:

1. Global Warming Potential (GWP):

Look for units using refrigerants with the low GWPs.

Most refrigeration systems leak. A low-GWP refrigerant ensures that if/when the unit leaks, its contribution to climate change is minimal. This is the single most important environmental metric. R-290 (GWP 3) and R-744 (GWP 1) are the best choices for HPHW, while R-32 (GWP 675) is currently the best mass-market choice for AC, as the transition to even lower GWP alternatives is still in progress for many AC systems.

The additional benefit of purchasing low GWP refrigerants is future-proofing. High-GWP refrigerants will become increasingly expensive, difficult to service, and difficult to dispose of as regulations tighten. Choosing a unit that uses a low-GWP refrigerant like R-32, R-290, or R-744 ensures your investment will be compliant and serviceable for decades.

2. Energy Efficiency (COP/EER):

While a refrigerant’s GWP is important, its efficiency determines your running costs and daily carbon emissions. Look for a high Coefficient of Performance (COP) for heating or Energy Efficiency Ratio (EER) for cooling, (but as always, be skeptical of manufacturer claims).

A highly efficient unit reduces demand on the electricity grid, leading to lower bills and a lower environmental footprint over the unit’s operating life.

3. Cost:

We of course need to balance these considerations with cost. What should we do if all we can afford is a HPHW unit that uses a poor quality refrigerant? On the one hand we want to encourage the heat pump over gas alternatives, but on the other we don’t want to install appliances with high GWP refrigerants.

I think the “lesser of two evils” is the heat pump. If the refrigerant escapes, it will have a lower environmental impact than burning gas for another 15 years (as well as the unburnt gas that escapes), and the efficiency gains mean energy bills will be drastically reduced.

The good news is that we can still find good quality appliances using natural refrigerants that are affordable. For example, while a Reclaim HPHW (which uses CO2) can be as much as 4 or 5 times the cost of other heat pumps, thankfully there are good quality mid-market units that use Propane that don’t break the bank.

The Right Choice For Your Wallet And The Planet

By considering both the immediate operating efficiency and the long-term environmental profile of the refrigerant, consumers can make informed choices that benefit both their wallets and the planet.

For more, read our dedicated guides to hot water heat pumps and air conditioning.