Heat Pump Auxiliary Heat — High Bill Cause

Professional Heat Pump Auxiliary Heat — High Bill Cause in Asheville & Western NC

What Is Auxiliary Heat?

Auxiliary heat — the "Aux Heat" indicator on your thermostat — means your heat pump is getting help from its backup heating source, typically electric resistance strips in the air handler. Unlike emergency heat, which bypasses the heat pump entirely, auxiliary heat works alongside it. The heat pump continues running and extracting heat from outdoor air, while the backup strips provide supplemental warmth to close the gap between what the heat pump can produce and what your home needs. Some amount of auxiliary heat usage is normal during WNC's coldest days.

When Aux Heat Activation Is Normal

Auxiliary heat commonly activates in three situations: when outdoor temperatures drop below your heat pump's balance point (the temperature at which the heat pump alone can no longer keep up), during the defrost cycle to prevent cold air from entering your home, and during a large temperature recovery (like when you raise the thermostat setting by several degrees at once). In these scenarios, brief aux heat usage is expected and not cause for concern.

When Aux Heat Means a Problem

If your "Aux Heat" light stays on for hours at a time, comes on when outdoor temperatures are above 35 to 40 degrees, or your electric bills have spiked dramatically, something is wrong. Common culprits include low refrigerant charge, a dirty outdoor coil, a malfunctioning reversing valve, a thermostat configured with an incorrect balance point, or a heat pump that's undersized for your home. Each of these forces the system to rely on expensive backup heat more than it should.

Reducing Aux Heat Usage Saves Money

Quality Comfort can optimize your heat pump system to minimize auxiliary heat usage. We verify refrigerant charge, clean coils, check the reversing valve, calibrate your thermostat's balance point setting, and ensure the system is sized correctly. For homes in the WNC mountains where temperatures regularly drop into the teens and twenties, upgrading to a cold climate heat pump can dramatically reduce or eliminate the need for auxiliary heat strips.