Do Heat Pumps Work in Illinois Below-Zero Winters?

In Illinois winters, heat pumps are often promoted as an efficient alternative to gas furnaces—especially because they move heat rather than create it from combustion. But many homeowners still worry about the same question: what happens when temperatures plunge below zero?

While heat pumps don’t “stop working” at extreme cold, their efficiency generally declines as outdoor temperatures fall. The key variable is how the system is designed and managed—particularly its capacity range, defrost strategy, and whether a supplemental heat source is available.