What is a common method to determine if auxiliary heat is needed?

Monitoring outdoor temperature is indeed a common method to determine if auxiliary heat is needed in a heat pump system. Heat pumps operate by transferring heat from the outside to the inside; however, their efficiency decreases as outdoor temperatures drop. When outdoor temperatures fall below a certain threshold, usually around 35°F to 40°F (depending on the system), the heat pump may struggle to provide enough warmth to meet the heating demands of the indoor space.

At this point, the auxiliary heat, which can be electric resistance heaters or another heating source, is activated to supplement the heat produced by the heat pump. This ensures the indoor environment remains comfortable during colder conditions when the heat pump alone may not suffice.

While assessing air flow, calculating indoor humidity, and checking refrigerant levels are important tasks for maintaining a heat pump system, they are not direct indicators of whether auxiliary heat is necessary in terms of temperature-dependent performance.