What Is Emergency Heat When a Heat Pump Fails?
Emergency Heat on a heat-pump thermostat is a backup heating setting. It tells the system to use its auxiliary heat source without asking the outdoor heat pump to run. It is not the same thing as emergency HVAC service.
Use the setting only when the heat pump is not operating or a technician has told you to. If you smell gas, see smoke, smell burning insulation, or the breaker trips again, stop troubleshooting and leave the unsafe area before contacting the appropriate utility or emergency service.
Backup mode
Emergency Heat uses the auxiliary heat source and disables the outdoor heat-pump call.
Not a repair
The setting can keep the home warm while you decide on service, but the outdoor failure remains.
Safety first
Gas odor, smoke, burning smell, or repeated breaker trips require a stop and a safety response.
Emergency Heat versus Auxiliary Heat
Auxiliary heat can come on automatically when a heat pump needs help during a cold period or a defrost cycle. Emergency Heat is selected manually and tells the thermostat to stop using the outdoor heat pump while it calls for the backup heat source.
That distinction matters because an occasional auxiliary-heat call is not proof that the heat pump has failed. Emergency Heat is a temporary operating choice after a problem, not a setting to use just because the weather is cold.
- Auxiliary heat may operate automatically when the system needs support.
- Emergency Heat is selected manually when the outdoor system cannot be used.
- The backup source may cost more to operate than the heat pump.
- Neither setting diagnoses or repairs the outdoor equipment.
What to check before choosing the setting
Look at the thermostat for an actual call for heat and note whether the indoor blower runs. Check the filter and the breaker once if it is safe to do so. Outside, observe whether the heat-pump fan runs, is silent, or is making an unusual noise, but do not remove panels or reach into the unit.
If there is ice on the outdoor coil during a normal defrost event, the system may need time to clear it. Thick ice that remains, no heat indoors, water where it should not be, or a unit that repeatedly trips protection deserves a diagnosis.
- Thermostat is set to Heat and shows a heat call.
- Filter is not visibly blocked.
- Outdoor behavior is noted without opening the cabinet.
- Gas, smoke, burning odor, and electrical symptoms are treated as safety issues.
The repair decision after the home is stable
Emergency Heat can be a bridge while you arrange service, but do not assume the heat pump is beyond repair. The diagnosis should identify whether the issue is power, airflow, controls, refrigerant, defrost operation, or a failed outdoor component.
Ask for the finding, the repair scope, and the test that will confirm normal heating afterward. If the unit is older or the repair is substantial, compare repair and replacement after the failure is explained.
- Request a diagnosis rather than a permanent Emergency Heat workaround.
- Ask whether the backup heat should remain on while waiting.
- Receive the repair recommendation in writing before approving work.
- Confirm heat-pump operation and thermostat mode after the repair.
Questions about Emergency Heat
What does Emergency Heat do?
It tells a heat-pump system to use its auxiliary heat source without operating the outdoor heat pump. It is a backup mode, not a repair.
Should I turn on Emergency Heat when it is cold?
Cold weather alone is not a reason to select it. Use it when the outdoor heat pump is not operating or a technician directs you to, then arrange a diagnosis.
Why is Emergency Heat more expensive to run?
The backup heat source may use more electricity than the heat pump. The exact effect depends on the equipment and operating conditions, so treat the setting as temporary.
What if I smell gas or burning near the system?
Leave the area and contact the gas utility or emergency service from a safe location. Do not keep resetting the system or investigate inside the cabinet.