A short history of the refrigerant transitions
The first big shift came when CFCs were found to damage the ozone layer. Under the Montreal Protocol they were phased out and replaced, in commercial refrigeration, mainly by HCFCs such as R22 and later by HFCs such as R134a and R404A. HFCs solved the ozone problem but many of them are powerful greenhouse gases. The Kigali Amendment, agreed in 2016, brought HFCs under the Montreal Protocol for a gradual phase-down.
That is why new equipment is moving to refrigerants that score low on both measures: hydrocarbons such as R290 and R600a, CO2, and some newer low-GWP synthetic blends. Each has its own trade-offs in flammability, pressure and efficiency.
Ozone depletion potential (ODP)
ODP compares a gas's ability to destroy stratospheric ozone with that of CFC-11, which is set at 1. CFCs such as R12 had high ODP and were phased out under the Montreal Protocol. HCFCs such as R22 have a much lower but non-zero ODP and are being phased out too. HFCs, hydrocarbons and CO2 contain no chlorine and have an ODP of zero.
Global warming potential (GWP)
GWP compares the warming effect of a gas with the same mass of carbon dioxide over a fixed period, almost always 100 years. CO2 is set at 1. A GWP of 1,430 means one kilogram of the gas, once released, traps as much heat over a century as 1,430 kilograms of CO2.
GWP values are revised as climate science improves, so you will see slightly different numbers in different sources. The Kigali Amendment uses 100-year values from the IPCC's Fourth Assessment Report (AR4), which are used in this guide.
Values for common refrigerants
| Refrigerant | Type | ODP | GWP (100-yr) |
|---|---|---|---|
| R22 | HCFC | 0.055 | 1,810 |
| R134a | HFC | 0 | 1,430 |
| R404A | HFC blend | 0 | 3,922 |
| R290 (propane) | Hydrocarbon | 0 | About 3 |
| R600a (isobutane) | Hydrocarbon | 0 | About 3 |
| R744 (CO2) | Natural | 0 | 1 |
Direct and indirect emissions
GWP covers only direct emissions: refrigerant that leaks during operation, service or disposal. Refrigeration also causes indirect emissions through the electricity it uses, because much of India's power still comes from fossil fuels. Engineers combine both into measures such as TEWI (total equivalent warming impact) over the equipment's life.
For a small, well-sealed cabinet the indirect emissions from electricity are often larger than the direct ones. For large systems with long pipe runs and big charges, leaks can dominate. Either way, the lowest-impact choice is a low-GWP refrigerant in an efficient, leak-tight system.
How to use GWP and ODP when buying
- Prefer zero-ODP refrigerants; HCFCs such as R22 are being phased out and servicing supply is shrinking.
- Prefer low-GWP refrigerants for new equipment, since HFC supply caps are measured in CO2-equivalent.
- Ask about refrigerant charge in kilograms; GWP × charge gives the system's CO2-equivalent if all of it leaked.
- Do not ignore efficiency: a low-GWP unit that wastes electricity can have a bigger overall footprint.
- Check safety class too; many low-GWP refrigerants are flammable or high-pressure and need trained service.
A quick worked example
A cabinet holding 0.5 kg of R404A has a refrigerant charge equivalent to about 1.96 tonnes of CO2 (0.5 × 3,922 kg). The same-size charge of R134a would be about 0.72 tonnes. A hydrocarbon cabinet holding 0.15 kg of R290 represents well under one kilogram of CO2-equivalent. That is the scale of difference HFC phase-downs are trying to capture.
Frequently asked questions
- Why do I see different GWP numbers for the same refrigerant?
- GWP values are updated in successive IPCC assessment reports. Regulations usually fix one set of values; the Kigali Amendment uses AR4 100-year values. Check which basis a document uses before comparing.
- Is a zero-ODP refrigerant automatically climate-friendly?
- No. HFCs such as R134a and R404A have zero ODP but high GWP. Look at both numbers, plus the energy efficiency of the equipment.
