Commercial Heat Pump Water Heaters Using CO2 Refrigerant

Heat pumps have become ubiquitous in our buildings because they are energy efficient and run on electricity rather than fossil fuels, an increasingly important consideration in areas where natural gas use is being restricted due to carbon emissions. The challenge is that the R-410a refrigerant typically used in heat pumps has a global warming potential (GWP) more than 2,000 times that of CO2, and with U.S. regulations for these high-GWP gases looming, manufacturers are looking at low-GWP alternatives.

Mitsubishi is now offering its Heat2O commercial heat-pump water heater, which uses carbon dioxide as a refrigerant. CO2 (R744) is not the right refrigerant for every application, but with low flammability, low toxicity, and a global warming potential of only 1—a combination other refrigerants have a hard time matching—its use in Heat2O offers us a glimpse of the potential future of commercial water heating.