What is the thermal balance point of a dual fuel heat pump?

The thermal balance point of a dual fuel heat pump refers to the specific outdoor conditions where the capacity of the auxiliary heat source, such as a gas furnace, matches the heating load of the building. At this point, the heat pump can provide all the required heating, but as outdoor temperatures fall further, the auxiliary heat becomes necessary to supplement the heat pump's output and maintain comfort inside the structure.

This balance is critical for efficient operation, as it defines when it is more efficient to rely on auxiliary heat rather than solely on the heat pump. Understanding this point helps in optimizing the system’s performance and ensuring proper heating efficiency during colder weather conditions while minimizing energy usage and costs.

The other options do not accurately define the thermal balance point. For example, operating at maximum efficiency is more related to a heat pump's performance characteristics rather than its operational relationship with auxiliary heat. The point where the compressor stops is related to system safety and performance cut-offs rather than the balance of heating loads. Finally, indoor comfort is a broader concept that encompasses more than just the thermal balance point, focusing instead on overall temperature and humidity conditions within the living space.