When winter temperatures drop, homeowners with heat pumps may notice their system switching between different heating modes. Two common terms associated with heat pump operation are auxiliary heat and emergency heat — but what do they mean, and when should each be used?
In this blog post, the heating experts at Moncrief Heating & Air Conditioning explain the difference between these settings and how understanding these key differences can help you avoid high energy bills while ensuring optimal comfort.
What Is Auxiliary Heat?
Auxiliary heat (or “aux heat”) is a backup heating mode that automatically activates when your heat pump alone isn’t sufficient enough to maintain the desired indoor temperature. This typically happens when:
- Outdoor temperatures fall too low for the heat pump to extract enough heat
- The heat pump is in defrost mode
- You increase the thermostat temperature significantly
Auxiliary heat uses electric resistance heating elements (or a gas furnace in a dual-fuel system) to supplement the heat pump. While effective, aux heat consumes more energy than standard heat pump operation, which can lead to higher utility bills if it runs frequently.
What Is Emergency Heat?
Emergency heat is a manual heating mode that bypasses the heat pump and relies solely on the backup heat source, such as electric resistance coils or gas furnace. This mode is intended for true emergencies, such as:
- A broken or malfunctioning heat pump
- Severe weather conditions causing the heat pump to fail
- Freezing temperatures when the heat pump is unable to operate
Because emergency heat is manually activated and runs without the heat pump, it’s far less efficient and should only be used when necessary.
Key Differences Between Auxiliary & Emergency Heating
The main difference between auxiliary heat and emergency heat lies in how they operate. Auxiliary heat turns on automatically when the heat pump needs extra help in extremely cold weather, supplementing it with electric resistance heating or a backup fuel source. It’s less efficient than normal heat pump operation but still necessary at times to maintain a comfortable temperature.
Emergency heat, however, is a manual setting used only when the heat pump has failed. It shuts off the heat pump entirely and relies solely on the backup heating source, making it far less efficient and best used as a short-term solution until the heat pump can be repaired.
How To Set Your Heating Mode
Understanding when to use auxiliary versus emergency heat is essential for maintaining comfort without wasting energy.
- Auxiliary heat should be left to operate automatically: Your thermostat will switch to aux heat when needed and turn it off when conditions improve. If you see “AUX HEAT” on your thermostat, it means the system is supplementing the heat pump temporarily.
- Emergency heat should only be used if your heat pump is malfunctioning or has completely stopped working: To turn it on, switch your thermostat to “Emergency Heat” mode. However, because this setting is expensive to run, you should contact a professional for repairs as soon as possible.
Call Moncrief for Heating Services
If your heat pump isn’t working properly or your home isn’t staying warm enough, don’t rely on emergency heat for too long. Moncrief Heating & Air Conditioning provides professional heating repairs, maintenance, and system replacements to keep your home comfortable all winter long. Whether you need help troubleshooting your heat pump or want to schedule a routine inspection, our expert technicians are here to help.
Schedule heating services in the Metro Atlanta area by contacting our team today!
