Refrigerants Compared
The refrigerant is the working fluid that lets a heat pump move heat from outside to inside. Which one a unit uses affects its environmental impact, its efficiency and achievable flow temperature, how it must be installed, and — increasingly — whether it can still be sold in the years ahead. This guide compares the refrigerants you will find across the database.
GWP (Global Warming Potential) measures how strongly one kilogram of the gas warms the planet over 100 years compared with one kilogram of CO₂ — so CO₂ is 1, and a refrigerant with a GWP of 2,000 is 2,000 times worse if it leaks. The safety class (ASHRAE) flags flammability and toxicity: A1 non-flammable and low toxicity, A2L mildly flammable, A3 highly flammable, B2L mildly flammable but toxic.
At a glance
GWP figures are 100-year values, rounded. They vary slightly between IPCC assessment reports — the EU moved from AR4 to AR5 values in 2025 — but the relative picture is unchanged.
The families, with pros and cons
Natural refrigerants with negligible GWP. R290 has become the default for new residential air source heat pumps, while R600a appears in large industrial high-temperature machines.
- Ultra-low GWP (≈3) — no meaningful climate impact if it leaks
- Excellent efficiency; high COP and SCOP
- Reaches high flow temperatures (up to ~75 °C), good for radiators and retrofit
- Not subject to the F-Gas phase-down — future-proof
- A3 — highly flammable, so charge limits, siting rules and a competent installer are essential
- Generally confined to outdoor monobloc units
- Charge-size limits can constrain very large indoor systems
A natural refrigerant that excels at producing very hot water and works well in cold weather. Common in commercial hot-water and high-temperature applications.
- GWP of 1 — the benchmark
- Non-flammable (A1)
- Excellent at high temperatures (70–90 °C) and in cold ambient air
- Very high operating pressures need specialised components
- Efficiency falls if the return-water temperature is high — best with a large temperature lift
- Mainly commercial and hot-water duties
The workhorse of large industrial refrigeration, also used for big water-source and district-heating heat pumps.
- Zero GWP and zero ozone impact
- Outstanding efficiency, especially at scale
- Decades of proven industrial use; inexpensive
- Toxic and mildly flammable (B2L) — not for domestic use
- Needs a plant room, leak detection and specialist design
- Incompatible with copper pipework
Synthetic but ultra-low-GWP fluids, mostly used in large commercial and high-temperature centrifugal machines.
- Ultra-low GWP (≈1 or below)
- R1233zd is A1 (non-flammable) and low-pressure — ideal for large high-temperature systems
- Not meaningfully affected by the phase-down
- Lower capacity per unit volume means larger equipment
- Higher cost; mainly commercial/industrial
- R1234ze is rated A2L (mildly flammable)
The fluorinated gases that dominated the last two decades. R32 is the current mainstream choice and far cleaner than the older R410A it replaced, but all are subject to the phase-down.
- Mature, widely available and well understood
- R32 has roughly a third of R410A's GWP and is a single compound (simple to recharge)
- R410A, R407C and R134a are non-flammable (A1)
- Mid-to-high GWP (675 up to ~2,088) — supply shrinks and prices rise under the phase-down
- R32's 675 GWP exceeds the EU's 150 limit for small monobloc heat pumps from 2027
- R410A/R407C/R134a are legacy choices being replaced
- R32 is A2L (mildly flammable)
Engineered mixtures that cut GWP while staying close to the equipment design of the gases they replace — R454B/R452B for R410A, R513A/R515B for R134a.
- Much lower GWP than the HFCs they replace (148–700)
- Near drop-in for manufacturers, easing the transition
- R513A, R515B and R448A are A1 (non-flammable)
- R454C sits below the key 150 GWP threshold
- Still contain fluorinated components, so still caught by the phase-down
- R454B, R454C and R452B are A2L (mildly flammable)
- Being blends, they have temperature "glide" and must be recharged carefully
The regulations
Fluorinated refrigerants are controlled by F-Gas regulations, which shrink the supply of high-GWP gases over time and ban them in new equipment where cleaner alternatives exist. Natural refrigerants (R290, CO₂, ammonia) and HFOs largely sit outside these limits. The picture differs across the UK.
European Union — Regulation (EU) 2024/573 (also applies in Northern Ireland)
Thresholds and category definitions are simplified here; some categories have safety-related exemptions. Existing installed equipment is unaffected — the bans apply to new products placed on the market.
Great Britain (England, Scotland, Wales)
Great Britain did not adopt the EU's 2024 regulation. It keeps the retained Regulation (EU) 517/2014 — the earlier HFC quota phase-down plus existing rules such as the GWP ≥ 2,500 servicing ban — so the EU's new product bans above do not currently apply in GB. Defra reviewed the rules and launched a consultation on a tighter GB HFC phase-down in November 2025; in May 2026 it confirmed it would not change the phase-down steps for the 2027 period yet, with a fuller response due later in 2026. The direction of travel mirrors the EU — tighter HFC limits and a shift to low-GWP and natural refrigerants — but the precise GB timeline is still being decided.
Northern Ireland
Under the Windsor Framework, Northern Ireland continues to follow the EU F-Gas Regulation, so the EU timeline above applies there.
All of this sits under the global Kigali Amendment to the Montreal Protocol, which commits developed countries to cutting HFC use to a small fraction of historic levels over the coming decades.
Where it's heading
The shrinking quota makes high-GWP gases such as R410A and R134a steadily scarcer and more expensive, pushing the whole market toward low-GWP and natural refrigerants. In practice:
- Residential heat pumps are converging on R290 (propane). It already dominates new monobloc ranges, has a GWP of 3, sits outside the phase-down and supports the higher flow temperatures UK retrofits often need — the most future-proof choice.
- R32 remains common today but its 675 GWP exceeds the EU's 150 limit for small monoblocs from 2027, so EU and Northern Ireland units are moving to R290. R32 is likely to persist longer in GB and in larger or split systems.
- Commercial and industrial systems are shifting to R290, CO₂, ammonia and HFOs (R1234ze, R1233zd, R515B) for large and high-temperature duties.
- For a new home system, R290 is the most future-proof option and often the strongest performer at higher flow temperatures.
- Already have an R410A or R32 unit? It's fine to keep running and servicing — the rules target new equipment, not existing installations — though servicing the highest-GWP gases will get costlier.
- Flammable refrigerants (A3, A2L) simply need a competent installer and correct siting; this is routine for modern units.
- Check the refrigerant when comparing models here — it shapes environmental impact, long-term serviceability and sometimes efficiency and flow temperature.
Reviewed June 2026. Regulations change and the GB rules are under review — always confirm the current position before making decisions. This guide is general information, not regulatory or professional advice.