CO₂ Heat Pump Water Heaters: US DOE Spotlights the Tech

The US Department of Energy (DOE) is drawing attention to CO₂-based heat pump water heaters as a promising solution for decarbonizing residential hot water production. Unlike conventional electric water heaters, heat pump models can achieve a coefficient of performance (COP) of 3 or higher — meaning they deliver three times more heat energy than the electricity they consume.

CO₂ (R-744) is a natural refrigerant with a global warming potential (GWP) of just 1, making it vastly more climate-friendly than synthetic refrigerants such as R-410A (GWP ~2,088). As F-gas regulations tighten in both the US and the EU, manufacturers are increasingly turning to natural refrigerant solutions like CO₂ for heat pump systems.

In Europe, CO₂ heat pump water heaters have already gained traction in markets such as Japan and parts of the EU. Countries like Austria and Germany are seeing growing adoption driven by energy price pressures and supportive policy frameworks, including heat pump subsidies under national climate programs.

The DOE's focus on this technology signals that CO₂ heat pump water heaters are moving from niche to mainstream. Homeowners and installers should expect a broader product range to emerge in the coming years, alongside incentives that make the upfront cost — typically higher than conventional units — more accessible.