Auxiliary heat provides a supplemental heating source for heat pump systems. It engages when the heat pump alone cannot maintain the set temperature, typically during periods of extreme cold. This supplemental heat is usually generated by electric resistance coils, similar to those found in an electric furnace. An example is when the thermostat is set several degrees higher than the current room temperature on a very cold day; the system might activate this supplemental function to quickly reach the desired temperature.
The function is crucial for maintaining comfort and preventing the system from working inefficiently. Prolonged reliance on the primary heat pump during severe cold can overwork the compressor, potentially shortening its lifespan and increasing energy consumption. Activating the supplementary heat ensures rapid temperature recovery and prevents the system from struggling to meet demand. Historically, these supplemental systems provided a fail-safe in situations where the primary heat pump technology was less reliable in extreme climates.