The short answer
Global warming potential (GWP) compares how much a gas warms the climate with the same mass of carbon dioxide, usually over 100 years. A refrigerant's GWP shows how much harm a leak would do, and it underpins the rules on refrigerants.
On this page
Refrigerant does no harm while it stays sealed inside an air conditioner. The concern is what happens if it escapes. Global warming potential, or GWP, is the number used to compare that risk between refrigerants, and it sits behind many of the rules about how they're used.
What GWP measures
GWP compares the warming effect of a gas with that of carbon dioxide, which has a GWP of 1 by definition. A gas with a GWP of 675 traps about 675 times as much heat as the same mass of carbon dioxide over the period measured, usually 100 years.
Two things give a gas a high GWP: how strongly it absorbs heat, and how long it stays in the atmosphere before breaking down.
The GWP of common refrigerants
| Refrigerant | Type | GWP |
|---|---|---|
| R22 | HCFC, no longer allowed for servicing | 1,810 |
| R410A | HFC blend | 2,088 |
| R32 | HFC | 675 |
| R290 (propane) | Natural refrigerant | 3 |
| Carbon dioxide | Reference gas | 1 |
The HFC figures are the ones used in the F-gas rules in Great Britain. R22 isn't an F-gas: as an ozone-depleting HCFC it falls under separate rules. Scientific assessments are updated from time to time and give slightly different figures, so you may see other numbers quoted elsewhere.
From GWP to CO2-equivalent
GWP turns a mass of refrigerant into a CO2-equivalent: the amount of carbon dioxide that would have the same warming effect. Multiply the mass by the GWP.
| Amount of refrigerant | CO2-equivalent |
|---|---|
| 1 kg of R32 | 675 kg |
| 1 kg of R410A | 2,088 kg |
| 1 kg of R290 | 3 kg |
So if a system lost 1 kg of R410A, the effect on the climate would be roughly the same as releasing two tonnes of carbon dioxide. The same loss from an R32 system would have about a third of that effect.
How GWP shapes the rules
In Great Britain, the F-gas rules use CO2-equivalent rather than kilograms for many of their thresholds. Mandatory leak checks, for example, apply to systems holding 5 tonnes CO2-equivalent or more.
| Refrigerant | Amount that reaches 5 tonnes CO2e |
|---|---|
| R410A | About 2.4 kg |
| R32 | About 7.4 kg |
A typical home split system holds roughly 0.5 to 1.5 kg of R32, far below that threshold.
The rules also reduce the amount of high-GWP refrigerant that can be sold over time. Rules on high-GWP refrigerants are tightening, which is the main reason manufacturers moved from R410A to R32, and why lower-GWP options, including natural refrigerants, are becoming more common.
Where you'll see it
Equipment containing an F-gas refrigerant carries a label saying so. It names the refrigerant and gives the amount both in kilograms and in tonnes of CO2-equivalent, so you can see a system's refrigerant in climate terms without doing the sum yourself. On an air conditioner, it's usually on or near the outdoor unit's rating plate.
What GWP doesn't tell you
GWP describes the refrigerant, not the whole system. It says nothing about how much electricity a system uses, which is the other part of its effect on the climate, and nothing about how likely it is to leak. A well-installed system that never leaks releases none of its refrigerant while it's in use.
To see both parts together, air conditioning and carbon emissions looks at electricity use and refrigerant side by side.
Related guides
- Refrigerants explainedA refrigerant is the fluid that carries heat around an air conditioner, boiling to absorb it and condensing to release it. Refrigerants differ in their pressures, efficiency, flammability and effect on the climate, which is why the choice matters.
- R32 refrigerantR32 is the refrigerant in most new wall-mounted systems. It carries heat efficiently, usually needs less of it than R410A, and has about a third of R410A's global warming potential. It is mildly flammable, so it's handled with specific precautions.
- Air conditioning and carbon emissionsAn air conditioner's effect on the climate comes from two places: the electricity it uses, and its refrigerant if it leaks. Using less electricity, running it when the grid is cleaner and keeping the system leak-free all reduce it.
- F-gas rules for homeownersF-gas rules in Great Britain require anyone installing, servicing or removing a split system to hold the right qualification, and ban releasing refrigerant. A typical home system is well below the size that needs mandatory leak checks.