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Air Source Heat Pump Refrigerant Types Explained

When you are choosing an air source heat pump, you will compare brands, efficiency ratings, noise levels, and prices. One thing most people overlook is the refrigerant — the chemical fluid that circulates inside the heat pump and actually carries the heat. It is arguably the most important component, and the type of refrigerant your heat pump uses has real implications for efficiency, environmental impact, future regulations, and long-term costs.

This guide explains the three main refrigerant types used in UK heat pumps — R410A, R32, and R290 — in plain terms, so you know what to look for and why it matters.

What Does Refrigerant Do in a Heat Pump?

Refrigerant is the working fluid that makes a heat pump function. It circulates in a closed loop, constantly changing between liquid and gas states to absorb and release heat. Here is the simplified cycle:

  1. Evaporation — cold liquid refrigerant absorbs heat from the outside air and evaporates into a gas
  2. Compression — the compressor squeezes the gas, raising its temperature significantly (from around 0°C to 60-80°C)
  3. Condensation — the hot gas releases its heat to the water in your heating system and condenses back into a liquid
  4. Expansion — the liquid passes through an expansion valve, dropping in pressure and temperature, ready to absorb heat again

Different refrigerants have different physical properties — boiling points, heat capacities, pressures — that affect how efficiently this cycle runs. For the full science behind this process, read our guide on how air source heat pumps work.

The Three Main Refrigerants in UK Heat Pumps

R410A: The Outgoing Standard

R410A was the dominant refrigerant in heat pumps and air conditioning systems for two decades. It is a blend of two hydrofluorocarbons (HFCs) — R32 and R125 — and it works well as a heat transfer fluid.

The problem is its environmental impact. R410A has a Global Warming Potential (GWP) of 2,088. That means one kilogram of R410A released into the atmosphere has the same warming effect as 2,088 kilograms of CO2. A typical domestic heat pump contains 2-4kg of refrigerant, so a leak represents a significant greenhouse gas emission.

Status in 2026: R410A is being phased out under UK and EU F-gas regulations. Most major manufacturers have already stopped using it in new residential heat pump models. You may still encounter it in older stock or commercial systems, but it should not be on your shortlist for a new installation.

R32: The Current Mainstream Choice

R32 (difluoromethane) is a single-component HFC that has become the standard refrigerant in most UK heat pumps installed today. It has a GWP of 675 — roughly one-third of R410A's impact. It also requires less charge (less refrigerant in the system) and has better thermodynamic properties, meaning heat pumps using R32 tend to be slightly more efficient.

Most current models from Samsung, Mitsubishi, Grant, Daikin, and others use R32. If you are getting a heat pump installed in 2026, there is a strong chance it will use R32.

Advantages of R32:

  • GWP of 675 — 68% lower than R410A
  • Better energy efficiency than R410A in most applications
  • Requires less refrigerant charge (smaller environmental impact if leaked)
  • Widely available, well-understood by installers
  • Proven technology with a strong track record

Disadvantages of R32:

  • Still an HFC with a GWP of 675 — well above the long-term regulatory target
  • Mildly flammable (A2L classification) — requires careful handling but is safe in normal operation
  • Will itself face phase-down pressure as regulations tighten further

R290: The Future

R290 is propane — yes, the same substance used in camping stoves and barbecues, though in a much more refined, pure form. It is a natural refrigerant with a GWP of just 3. To put that in perspective: R290 has 0.14% of R410A's global warming impact and 0.4% of R32's.

R290 also has excellent thermodynamic properties. Heat pumps using R290 can achieve very high efficiency ratings, particularly in cold weather — which is exactly when you need your heat pump to perform best.

Advantages of R290:

  • GWP of 3 — effectively climate-neutral as a refrigerant
  • Excellent efficiency, particularly at low ambient temperatures
  • Natural substance — no synthetic chemicals, no ozone depletion
  • Future-proof against any foreseeable F-gas regulation changes
  • Already used in the best-selling heat pump in the UK (Vaillant aroTHERM plus)

Disadvantages of R290:

  • Flammable (A3 classification) — requires specific safety measures in system design
  • Charge limits restrict the amount of R290 in a system, limiting maximum capacity from a single unit
  • Slightly higher unit cost for some R290 models
  • Not all installers are trained on R290 systems yet

Is R290 Safe?

This is the question everyone asks, and rightly so. Propane is flammable — that is a fact, not something to dismiss.

However, the quantities involved are very small. A typical R290 heat pump contains 500g to 1.5kg of propane. For comparison, a standard barbecue gas bottle contains 13kg. The refrigerant is in a sealed, pressurised system that is tested to withstand far more than normal operating pressures.

R290 heat pumps are designed with multiple safety features:

  • The refrigerant circuit is entirely contained in the outdoor unit (monoblock design) — no flammable refrigerant enters your home
  • Leak detection sensors shut the system down if any refrigerant escape is detected
  • The outdoor unit must be positioned with adequate ventilation to ensure any leaked gas disperses safely
  • All R290 units must meet strict safety standards (EN 378, IEC 60335-2-40)

Millions of R290 heat pumps are installed across Europe, with an excellent safety record. The Vaillant aroTHERM plus, which uses R290, is the best-selling heat pump in the UK and across several European markets.

F-Gas Regulations: What Is Changing?

The UK (post-Brexit) and the EU both have F-gas regulations that progressively phase down the use of high-GWP refrigerants. The key regulatory milestones affecting heat pumps:

Current Rules

  • R410A is being actively phased out — supply restrictions and quota reductions are making it increasingly expensive and hard to source
  • R32 is permitted but faces future restrictions as a mid-GWP refrigerant
  • R290 and other natural refrigerants face no restrictions

What This Means for You

If you install a heat pump with R410A, you may face difficulties getting it serviced or topped up in years to come as the refrigerant becomes scarce and expensive. R32 is safe for the foreseeable future — certainly for the lifetime of any heat pump installed today. R290 is completely future-proof from a regulatory standpoint.

The practical advice: choose R32 or R290. Both are excellent choices today. R290 is the more forward-looking option, but R32 is proven, widely available, and will serve you well for 15-20 years.

How Refrigerant Choice Affects Your Heat Pump Decision

Efficiency

R290 heat pumps tend to achieve the highest efficiency ratings, particularly in cold weather. The Vaillant aroTHERM plus (R290) achieves SCOP ratings above 4.0 in most UK conditions. R32 models are close behind, with SCOP ratings typically between 3.5 and 4.0. R410A models are generally the least efficient of the three.

Cost

R32 models are currently the most competitive on price, with a wide range of brands and price points. R290 models tend to sit at a modest premium — typically £500-£1,500 more than equivalent R32 units. Whether that premium is worth it depends on your priorities.

Maintenance

All heat pumps need periodic maintenance. The refrigerant type does not significantly change the maintenance schedule, but it can affect costs if a refrigerant leak ever occurs. R410A is becoming expensive to source. R32 is reasonably priced. R290 (propane) is very cheap as a raw material.

Environmental Impact

If minimising your environmental footprint is a priority, R290 is the clear winner. Its GWP of 3 is negligible. R32 at 675 is much better than R410A but still represents a meaningful greenhouse gas if leaked. In the context of a sealed system that is properly maintained, the actual risk of significant leakage is low for all three — but the principle matters to many people.

Which Brands Use Which Refrigerant?

Here is a snapshot of the main brands and their refrigerant choices in 2026:

  • Vaillant aroTHERM plus — R290
  • Samsung EHS Mono — R32
  • Grant Aerona3 — R32
  • Mitsubishi Ecodan — R32 (some newer models moving to R290)
  • Daikin Altherma 3 — R32 (R290 models in development)
  • NIBE — R290 in several models
  • Bosch — R290 in newer ranges

The industry is clearly moving towards R290. Expect most major brands to offer R290 options within the next two to three years. For a broader comparison of brands, read our complete guide to air source heat pumps.

What to Ask Your Installer

When getting heat pump quotes, ask these refrigerant-related questions:

  1. What refrigerant does this model use? — Avoid R410A. Accept R32 or R290.
  2. What is the refrigerant charge? — Less is generally better from an environmental standpoint.
  3. What happens if there is a refrigerant leak? — Understand the process and cost for a top-up or repair.
  4. Is the system a monoblock or split? — Monoblock R290 systems keep all refrigerant outdoors, which is the safest configuration.

To get quotes from qualified installers in your area, use our free quote service.

Frequently Asked Questions

What refrigerant do most UK heat pumps use?

In 2026, the majority of new residential heat pumps installed in the UK use R32. R290 (propane) is the fastest-growing segment and is used by several leading models including the Vaillant aroTHERM plus. R410A is being phased out and should be avoided in new installations.

Is R290 propane dangerous in a heat pump?

R290 is flammable, but the quantities in a heat pump are very small (typically under 1.5kg), the system is sealed, and modern R290 heat pumps include leak detection and automatic shutdown. Millions are installed safely across Europe. The refrigerant stays in the outdoor unit and never enters your home.

Will R32 be banned?

There is no current ban on R32, and it is expected to remain available and legal for the foreseeable future. However, F-gas regulations will continue to tighten, and the long-term direction is towards natural refrigerants like R290. Any R32 heat pump installed today will be fully supported throughout its lifetime.

Does the refrigerant type affect running costs?

Indirectly, yes. R290 heat pumps tend to be slightly more efficient, which means slightly lower electricity consumption. The difference is typically 5-10% compared to R32 — enough to save £30-£60 per year on a typical household's heating bill.

Can I change the refrigerant in my existing heat pump?

No. Heat pumps are designed for a specific refrigerant. You cannot swap R410A for R32, or R32 for R290. The compressor, expansion valve, and heat exchangers are all optimised for the specific refrigerant's properties. If you want a different refrigerant, you need a different heat pump.

What happens if my heat pump leaks refrigerant?

A refrigerant leak will cause your heat pump to lose efficiency and eventually stop heating effectively. Your installer or a qualified engineer can detect, locate, and repair the leak, then recharge the system. For R410A systems, the cost of replacement refrigerant is increasing. R32 and R290 are much more affordable.