So why is GM switching from R-134 to HFO-1234yf? The new refrigerant provides lower “global warming potential” (GWP), which is to say it is better for the environment. It cools as well or better than R-134.
Current automotive air conditioners use hydrofluorocarbon HFC-134a, which has a GWP of 1430. The European Union’s Mobile Air Conditioning Directive requires that, starting in 2011, all new vehicle models use a refrigerant with a GWP below 150, and by 2017, all new automobiles sold in Europe will be required to use a low-GWP refrigerant. The new refrigerant, developed by DuPont and Honeywell, has a GWP of 4, which is 97% less GWP than the new regulation requires.
Remember the old R-12? It had a GWP of 8100. So yes, R-134 was better than R-12, but HFO-1234yf is a large improvement over both.
The other alternative was CO2 (R744); here is a comparison of HFO-1234yf and R744:
| HFO-1234yf | CO2 (R744) | |
| Environmental Impact | Lower lifetime GHG emissions than 134a or CO2 |
20% more lifetime greenhouse gas emissions than 1234yf |
| Atmospheric Lifetime | 11 days |
>500 years |
| Compatibility with Current A/C Equipment | Yes, with minor change |
No; new high-pressure system required |
| Cooling Efficiency | Comparable to 134a in all climates |
Less efficient in hot climates where A/C is needed and used most |
| Ease of Adoption | High; minimal additional design changes or delay |
Low; significant engineering and re-tooling required |
| Safety | Safe for use in automotive air conditioning applications |
Safe for use in automotive air conditioning applications |
So it looks like HFO-1234yf is a good choice going forward. A concern has been the relatively high cost of the new refrigerant, but with widespread usage and new factories online that should resolve itself (supply and demand).