Many homeowners rely on heat pumps to keep their homes comfortable year-round. However, unexpected weather or equipment failure can put your system to the test. One crucial feature is heat pump emergency mode—a setting designed to deliver supplemental heating when your main heat pump cannot. Understanding how emergency heat works, when to use it, and best practices for operation can help protect your system and keep your household safe and warm.
What Is Heat Pump Emergency Mode?
Emergency mode on a heat pump refers to a special heating setting, often labeled “EM Heat” or “Emergency Heat” on your thermostat. This feature activates a backup heat source—usually electric resistance coils or a gas furnace—when the main heat pump cannot provide enough heat or has malfunctioned. Unlike the standard “Heat” setting, emergency mode bypasses the outdoor compressor entirely and relies solely on auxiliary heat to warm your home.
How A Heat Pump System Works Vs. Emergency Heat Mode
Normal heat pump operation transfers heat from outside air into your home, even in cold conditions. All-electric heat pumps can struggle when outdoor temperatures drop near or below freezing. If the main system can’t maintain your thermostat’s temperature or the outdoor unit fails, emergency heat steps in to prevent a complete heat loss.
| Mode | Heat Source | Energy Efficiency | When Used |
|---|---|---|---|
| Normal | Outdoor compressor (heat pump) | High | Mild to moderately cold weather |
| Auxiliary | Heat pump + backup (auto) | Medium | Below freezing, but pump still running |
| Emergency | Backup heat only | Low | Outdoor unit failure or extreme cold |
Understanding The Thermostat Settings
Most programmable thermostats for heat pumps have three heating settings: Heat, Aux Heat, and EM Heat. The Aux Heat setting is automated—triggered when your system needs supplemental energy to reach your temperature setting. Emergency Heat is manual, used when you intentionally switch the system to backup heat due to an outage or problem with the heat pump itself.
It’s crucial to only use emergency heat if absolutely necessary, as it is less efficient and will quickly increase your electric bill, or gas use, depending on your backup.
When Should You Use Emergency Heat Mode?
Emergency heat mode is intended for specific situations. Here are common scenarios when you might need it:
- Main Heat Pump Failure: If the outdoor unit malfunctions, freezes over, or stops working entirely, use EM Heat to prevent home temperatures from dropping dangerously low until repairs are made.
- Severe Cold Spells: If your pump cannot maintain the thermostat set point during an extreme cold snap, switch to EM Heat as a temporary measure.
- Maintenance Or Repairs: Turn on emergency heat if technicians need to service or replace components on your outdoor unit.
- Ice Accumulation: In rare cases of significant icing on the outdoor unit that cannot be cleared with defrost cycles, it’s safer to use emergency mode and call for service.
Do not use EM Heat as a routine backup—it’s not designed for sustained use as your primary heating method.
How Emergency Heat Differs From Auxiliary Heat
Auxiliary heat engages automatically when the heat pump can’t keep up with heat demand but hasn’t failed. Emergency heat is a manual activation that shuts down the outdoor unit entirely. The distinction affects energy efficiency and potential repair needs, so homeowners should know the difference.
- Auxiliary Heat: Works automatically with the main pump; less expensive to run.
- Emergency Heat: Runs the backup only—much higher energy costs, so best for true emergencies.
Types Of Backup Heat For Emergency Mode
The kind of emergency heating your system uses depends on your installation and climate:
- Electric Heat Strips: Common in heat pump systems in milder climates; electric coils heat air directly but use much more electricity.
- Gas Or Oil Furnace: Used in dual-fuel systems; activates a traditional furnace when heat pump can’t keep up or fails.
- Hydronic Systems: Some homes use hot water coils as an emergency backup, rarely seen in residential settings.
Most American homes with heat pumps use electric heat strips for emergency heat, and these can cause a significant spike in utility bills.
Recognizing When Your Heat Pump Needs Emergency Mode
Symptoms that warrant switching to EM Heat include:
- No Heat: If your home is not getting any heat on the standard “Heat” setting, especially if the outdoor unit does not run.
- Unusual Noises Or Smells: Grinding, buzzing, or burning odors could mean mechanical failure.
- System Error Codes: Some smart thermostats display error codes advising to switch to emergency mode.
- Heavy Outdoor Ice Accumulation: If defrost cycles don’t clear thick ice, and air does not flow from vents as expected.
If in doubt, contact your HVAC technician. Prolonged use of emergency mode can cause high bills and sometimes hasten wear on backup components.
Step-By-Step: How To Activate Emergency Heat Mode
Switching your thermostat to emergency heat is a simple process:
- Locate your thermostat and look for the EM Heat or Emergency Heat setting.
- Toggle the switch or select the EM Heat option on the menu. The display should confirm the change.
- Monitor your home’s temperature and listen for the backup system engaging (you may hear different sounds compared to normal heating).
- Call your HVAC company as soon as possible to address the underlying heat pump problem.
Do not leave your system in EM Heat longer than needed.
How Long Can Emergency Heat Run Safely?
Emergency heat is only meant for temporary use. Most manufacturers recommend only running EM Heat for a few hours to several days until your primary system can be repaired. Extended use can overtax electrical circuits, dramatically increase bills, and may compromise backup equipment.
If outside temperatures are dangerously low, keeping EM Heat running to maintain safety is acceptable, but schedule repairs promptly.
Energy Costs Of Emergency Heat Mode
Activate emergency heat only when absolutely necessary because it is considerably more expensive per hour than using the heat pump.
- Electric Heat Strip Systems: May cost 2-5 times more per hour than regular heat pump operation.
- Gas Backup: Dual-fuel systems are more efficient in very cold weather, but costs can still rise with heavy usage.
- Electric utilities may charge higher winter rates, amplifying cost concerns.
Monitoring your energy bill and using the EM Heat function judiciously will help contain expenses.
Common Myths About Emergency Mode On Heat Pumps
- “EM Heat Makes My Home Warmer, Faster” – Actually, EM Heat simply engages a different (less efficient) heat source. The heating may not be faster than normal operation.
- “Aux Heat and EM Heat Are The Same” – They use similar backup elements, but EM Heat is a manual override. Auxiliary heat works with the pump and is efficient when properly controlled.
- “It’s Safe To Run All Winter” – Extended use of emergency heat is not recommended as a main source—it’s a temporary solution during outages or repairs.
Correctly using your settings preserves your system and saves on costs.
How To Prevent Needing Emergency Heat Mode
Preventative care reduces the odds you’ll need to rely on emergency mode:
- Regular Maintenance: Annual professional inspections help keep your system healthy.
- Air Filter Changes: Clean or replace filters every 1–3 months to avoid airflow trouble.
- Keep Outdoor Unit Clear: Remove ice, snow, and debris from around the outdoor compressor for efficient operation.
- Upgrade If Needed: Consider a modern, dual-fuel or cold-climate heat pump if you live in a region with harsh winters.
Routine attention extends your system’s life and minimizes emergencies.
Modern Smart Thermostats And Emergency Mode
Many newer thermostats automatically notify you or your HVAC provider if the system detects an issue requiring emergency heat. Features may include:
- Real-time error codes and alerts sent to your smartphone
- Automatic switchover to backup in case of temperature drops
- Remote control and monitoring of emergency mode status
Smart thermostats simplify emergency handling and help prevent complications from unnoticed system breakdowns.
How Emergency Mode Affects Indoor Air Quality
Switching to emergency heat with electric strips dries indoor air more than typical heat pump operation. Long periods on EM Heat may worsen dry skin, sinus discomfort, and static electricity.
- Run a humidifier if your home feels dry during extended EM Heat use.
- Change furnace filters regularly to improve air quality, especially if your backup is gas- or oil-fired.
Good air quality practices are important during winter, especially in emergencies.
Is Emergency Heat Safe For Pets And Children?
Yes—when used correctly, EM Heat is safe for all household members. However, always observe these precautions:
- Keep children and pets away from heating vents, which may become hotter than usual.
- If backup heat uses combustion (gas/oil), ensure carbon monoxide alarms are working.
Safety checks are important before and during emergency use.
When To Call An HVAC Professional
Call for professional help immediately if:
- No heat is produced on any setting and temperatures inside are dropping fast.
- There are signs of electrical or gas problems (burning smells, tripped breakers, repeated fuse issues).
- Your system stays stuck in EM Heat and won’t return to normal heat.
- Outdoor components show visible damage or excess ice buildup.
Prompt service prevents permanent damage and restores comfort quicker.
Choosing The Right Heat Pump For Your Climate
If your current system frequently requires emergency mode, it may be undersized or outdated. Consider:
- Heat pumps rated for colder regions—these can run efficiently below 10°F (-12°C).
- Dual-fuel systems with furnace backup—more efficient and cost-effective for areas with deep cold snaps.
- Consulting a certified HVAC contractor for a capacity check and upgrade recommendations.
Modern systems reduce emergency mode dependence and lower long-term costs.
Emergency Mode FAQ And Quick Reference
| Question | Answer |
|---|---|
| What does EM Heat mean? | Emergency Heat – the thermostat setting that uses only your backup heating source. |
| How do I know if my heat pump is on EM Heat? | Your thermostat will display “EM Heat” or “Emergency Heat.” The outdoor unit will not run. |
| Is it okay to use EM Heat all winter? | No—this is expensive and puts strain on your backup system. Use only until repairs are made. |
| Can I switch back to regular heat after EM Heat? | Yes, once your outdoor unit is fixed, simply set your thermostat to “Heat.” |
| What should I do if EM Heat doesn’t work? | Call an HVAC technician—your system may have a more serious issue needing urgent repair. |
Keep this guide handy for quick troubleshooting and safe usage.