HFC-134a is more energy efficient than CO2 in air-cooled stationary air conditioning equipment, according to an in-depth German study of HFC-134a and CO2 systems (“Betrachtungen zum Energieverbrauch von luftgekühlten Klimageräten mit dem Kältemittel CO2 unter praxisnahen Bedingungen” *).
Compared to HFC-134a, all twelve different CO2 systems studied were found to have a higher energy demand.
Because CO2 is intrinsically less energy efficient than HFCs, it is often proposed to incorporate additional technical elements, sometimes quite costly. According to the author improvements, such as defining an optimal high pressure level or using an additional internal heat exchanger, had only a marginal effect, not worth the extra cost involved.
In conclusion, the author praises the EU F-Gas Regulation with its focus on system tightness and end-of-life recovery and recycling.