Thermostat Emergency Heat Setting: How It Works and When to Use It
Learn how the thermostat emergency heat setting works, when to use it, and practical tips for managing energy costs while keeping your home warm during cold snaps.
Thermostat emergency heat setting is a mode that activates electrical resistance heating when the heat pump cannot meet heating demand. It provides rapid warmth but at a higher energy cost.
What is the thermostat emergency heat setting and when does it activate?
The thermostat emergency heat setting is a dedicated mode on heat pump systems that kicks in when the heat pump alone cannot achieve the indoor temperature you’ve programmed. In this mode, the system relies on electric resistance heating to supplement or replace the heat pump output. It is designed as a safety backup to maintain comfort during extreme cold, refrigerant issues, or a malfunction that limits heat pump performance. This feature is common in modern thermostats and heat pump blends, and it is typically labeled as Emergency Heat or Em Heat. According to Thermostat Care, emergency heat should be used only when necessary because it bypasses the heat pump’s efficiency and uses electricity directly to generate heat.
In practice, you’ll notice a change in the thermostat display when emergency heat engages, often marked by an EM or Emergency Heat indicator. The transition may feel abrupt, but it is a deliberate safety mechanism to ensure your living spaces stay warm even if the primary heating source is temporarily unavailable. If you see EM on your display without an obvious cause, it may indicate a control setting issue, a sensor fault, or a malfunction in the outdoor unit that is preventing the heat pump from operating normally.
Questions & Answers
What is the thermostat emergency heat setting?
The emergency heat setting is a safety backup mode for heat pumps that uses electric resistance heating when the heat pump cannot meet heating demand. It ensures warmth but at higher energy costs. This mode should be used only during extreme conditions or when the heat pump is offline.
Emergency heat is a backup mode for heat pumps that uses electric resistance heating when the heat pump can’t meet demand. It keeps your home warm but costs more to run.
Is it safe to leave emergency heat on all night?
Leaving emergency heat on for extended periods can dramatically raise electricity bills and may overheat spaces if not monitored. Use it short term and rely on the heat pump again once temperatures stabilize.
It is not ideal to leave emergency heat on overnight because it uses more energy. Use it briefly and return to normal operation when possible.
Will using emergency heat damage my heat pump?
Emergency heat itself does not typically damage the heat pump, but it puts extra stress on electrical components and is less efficient. Prolonged use can wear parts faster and reduce system efficiency.
Emergency heat won’t usually damage the heat pump, but it is not as efficient and can wear electrical parts faster if used long-term.
How can I tell if my system is using emergency heat?
Look for an EM or Emergency Heat indicator on your thermostat. Your outdoor unit also sounds different or runs more frequently when emergency heat is active. If you’re unsure, check the thermostat’s energy mode settings.
Check your thermostat display for EM and listen for more fan or heater activity which signals emergency heat is on.
When should I switch off emergency heat?
Switch off emergency heat as soon as the heat pump can meet your comfort needs again, typically after outdoor temperatures rise or after a technician resolves a heat pump issue. Resume normal operation to recover efficiency.
Turn off emergency heat once the heat pump can handle heating again and you’re comfortable. Then use normal mode for efficiency.
Can I improve efficiency while using emergency heat?
While emergency heat is active, focus on quick, cost aware adjustments such as lowering the thermostat by a degree or two if safe, sealing drafts, and using supplemental blankets. These steps can reduce cooling demand once normal operation resumes.
You can reduce energy use by lowering the set temperature slightly and improving home insulation until normal heat pump operation returns.
What to Remember
- Put emergency heat on only when the heat pump cannot keep up.
- Expect higher energy use and costs when emergency heat is active.
- Know how to turn emergency heat off once normal operation resumes.
- Check for system issues if emergency heat engages unexpectedly.
- Consult professional service if you frequently rely on emergency heat.