Hybrid Heat Pumps Offer Practical Compromise

For those concerned about GHG emissions, installing an electric heat pump as the primary heating source with a gas furnace for backup heat is actually a great choice. Consider a 2020 study from the University of California, Davis, Western Cooling Efficiency Center, which found that “in single-family residential buildings in California, the hybrid heating system (heat pump paired with a low NOx furnace for auxiliary heat) reduced NOx emissions by 95%-100% and CO₂ emissions by 67%-69% compared to a low NOx furnace … this study shows hybrid heating systems are a viable alternative to reduce NOx and CO₂ emissions.”

That represents a significant decrease in emissions when compared to scenarios where the homeowner relies solely on the gas furnace for heat. In a hybrid system, the study noted, the heat pump operates during mild temperatures. “As the outdoor air temperature drops and the heat pump can no longer meet the heating load of the building, the system turns off the heat pump and switches to the natural gas furnace. By reducing the number of hours in the year that the furnace must operate, the hybrid heating system reduces the annual NOx emissions of the furnace.”

Keeping an existing gas furnace in place also alleviates some of the anxiety customers — and contractors — may have, if they’re not comfortable with newer heat pump technology. According to a recent survey conducted by Midea, approximately 80% of homeowners were familiar with the concept of a heat pump. However, when asked whether they knew that a heat pump could manage 100% of the heating demand at -4°F, only 4% were aware of this capability. When contractors were asked that last question, only 30% knew that heat pumps could perform well in ultra-cold climates.

Until customers and contractors start hearing a steady stream of good news from friends and family about how the newer heat pumps are keeping them warm in winter, it’s a good idea to hang onto the furnace as backup. This hybrid approach is also likely to be more cost-effective for homeowners, as the use of electric supplemental heat can significantly increase utility bills. Contractors may also be hesitant to recommend heat pumps as the primary heat source, given their experiences in previous decades, when there was a similar push to move from furnaces to heat pumps. It turns out that the technology of the day was not very effective in cold climates, often leaving customers chilly — and angry — once winter rolled around.

That’s why it’s a good idea to take things slow. As Stephen Yurek, president of AHRI, noted during a panel discussion at this year’s AHR Expo in Chicago, “Instead of replacing a cooling system with another air conditioner, put in a heat pump and maintain that furnace. The heat pump can provide heating and cooling, and the furnace can be used for backup, rather than electric resistance heat. Then the next time, 15 or 20 years down the road when it’s time to replace the system, the electric grid will be cleaner and better, and the homeowner may be ready to transition to a heat pump only.”

At the same panel discussion, Ginger Scoggins, P.E., president of ASHRAE, agreed, adding that “dual fuel is absolutely a bridge to the future.”

Taking a gradual approach to the electrification transition allows for both environmental progress and consumer (and contractor) readiness, making hybrid systems a smart choice.