Emergency heat on a heat pump is a crucial backup function that homeowners need to understand, especially during harsh American winters. Engaging this setting is sometimes necessary when regular heat pump operation is compromised by low temperatures or mechanical issues. This article explores what emergency heat means, how it works, when to use it, and how it affects your energy bills and system lifespan. Homeowners will also find practical tips for optimal use and efficiency, empowering confident decision-making when weather or emergencies strike.
Summary Table: Key Features Of Emergency Heat On Heat Pumps
| Aspect | Description |
|---|---|
| Definition | Backup heating mode replacing the heat pump’s primary system in emergencies |
| Activation | User-enabled, typically via thermostat “EM Heat” setting |
| Heating Source | Electric resistance coils or alternate fuel-powered system |
| Energy Efficiency | Significantly less efficient than normal heat pump operation |
| When To Use | During extreme cold, mechanical failure, or when advised by a technician |
| Duration | Short-term use recommended due to high energy costs |
Heat Pumps: How They Provide Primary And Backup Heating
Heat pumps work by transferring heat from outside to inside a home, even in cold weather. In most US climates, they are an energy-efficient alternative to furnaces or baseboard heaters. Modern heat pumps can perform double duty, offering both heating and cooling capacities through a single outdoor unit.
However, during extremely cold periods—or if the primary heating system fails—a backup heating source is required to maintain comfort indoors. This is where emergency heat, sometimes called “EM Heat” or auxiliary heat, becomes important.
Understanding Emergency Heat On A Heat Pump
Emergency heat is a secondary heating option designed to keep you warm when your primary heat pump cannot keep up or stops working. It bypasses the normal heat pump function and activates an alternate heating method. This setting is often found on modern programmable thermostats as “EM Heat” or “Emergency.”
Unlike automatic auxiliary heat, which the heat pump can engage itself if temperatures drop too low, emergency heat is typically a manual setting that homeowners or technicians must activate. It is not intended for long-term or regular use due to its high energy consumption.
How Does Emergency Heat Work?
When the EM Heat option is activated, the heat pump’s outdoor compressor unit shuts off completely. Your thermostat instead turns on an electric, natural gas, or oil-powered backup heating system—most commonly electric resistance coils in American homes.
Electric resistance heating elements work like a giant toaster: electricity passes through metal coils, which get hot and transfer heat through the air handler and into your living spaces.
Some older or larger systems may use a gas or oil furnace as their emergency backup, but the majority of modern residential heat pumps use electric strips for emergency heating.
Emergency Heat Vs. Auxiliary Heat: What’s The Difference?
Homeowners sometimes confuse “emergency heat” with “auxiliary heat,” but the difference is significant:
- Auxiliary Heat: Automatically engages when the heat pump alone cannot meet the heating set point, such as during very cold weather. It runs together with the heat pump’s primary system.
- Emergency Heat: Manually activated by the user or technician. Only the backup heater runs, and the heat pump’s outdoor unit remains off.
Auxiliary heat is a built-in support that boosts heat during normal operation, while emergency heat is a last-resort feature used when normal operation is impossible or ineffective.
When Should Homeowners Use Emergency Heat?
Because emergency heat is significantly less efficient, experts recommend using it only when necessary. Common scenarios include:
- Primary heat pump is broken, iced over, or malfunctioning
- Temperatures have dropped so low (usually 25°F or below) that the heat pump cannot extract enough heat from outdoor air
- A technician instructs you to use emergency heat pending repairs
- Your heat pump outdoor unit is undergoing service or cleaning
Generally, do not use emergency heat simply because it’s cold outside—allow the system to switch to auxiliary automatically unless a malfunction occurs. Always consult your HVAC technician if you’re uncertain.
How To Activate Emergency Heat On Your Thermostat
Most programmable thermostats, especially those compatible with heat pumps in the US, have a dedicated “EM Heat” or “Emergency” button or setting. To enable emergency heat:
- Locate the EM Heat or Emergency mode on your thermostat display or controls.
- Select or press the mode to activate it.
- Your thermostat should indicate emergency heat is in operation with a notification, icon, or indicator light.
- Contact an HVAC professional immediately if you have not already addressed the underlying issue.
**Tip:** Never leave your system on emergency heat indefinitely due to increased energy use and potential damage to the backup heater.
Efficiency And Cost Considerations Of Emergency Heat
While heat pumps are exceptionally efficient under normal conditions, emergency heat is not. Electric resistance heaters convert nearly all the electricity they consume into usable heat, but they use two to three times more energy (or even more) than standard heat pump operation.
If your electricity comes from the grid, this can result in much higher utility bills. A heat pump operating under emergency heat may cost three to four times as much to operate per hour compared to its normal mode.
| Heating Mode | Efficiency (COP*) | Estimated Cost |
|---|---|---|
| Standard Heat Pump | 2.5–4.0 | Low to moderate |
| Emergency Heat | 1.0 | High |
*COP: Coefficient Of Performance (higher is better)
**Key takeaway:** Only use emergency heat when absolutely necessary to avoid energy waste.
Common Causes That Require Emergency Heat
Several issues might make it necessary to activate the emergency heat mode. Being able to identify these scenarios helps homeowners act promptly:
- Ice Or Frost Buildup: Outdoor units can freeze up during long cold snaps, blocking normal operation and triggering the need for backup heating.
- Mechanical Failure: If the heat pump’s outdoor compressor or fan stops working due to electrical failure, damage, or age, heating capacity falls off completely.
- Loss Of Refrigerant: A refrigerant leak prevents the heat pump from transferring heat, requiring immediate service and possible emergency heat use.
- Prolonged Extreme Cold: In rare events, temperature dips far below the design capacity of your heat pump, making backup heat a necessity until weather improves.
If any of these occur, contact a licensed HVAC professional immediately rather than relying on emergency heat for an extended period.
What To Expect When Running Emergency Heat
Most homeowners notice rooms will warm slower and that their electric bills rise if emergency heat stays on for long periods. The system’s air handler may run more frequently or even continuously in an attempt to meet your set point.
Additionally, the outdoor unit will stop making noise, as it is disabled during emergency operation.
Homes with gas or oil emergency heat sources may hear the furnace ignite or run just like a standard central furnace.
Best Practices To Minimize Emergency Heat Reliance
To avoid unnecessary use of emergency heat, consider these proactive steps for home comfort and energy savings:
- Schedule regular HVAC maintenance to keep your heat pump clean, charged, and working efficiently.
- Seal air leaks and insulate attics, walls, and crawlspaces to reduce heat loss in extreme cold.
- Upgrade to a modern, cold-climate heat pump if your current system struggles in winter; new models have improved capacity at low temperatures.
- Monitor your thermostat and learn how your system responds to outside conditions; use temperature setbacks wisely to avoid unnecessary strain.
Frequently Asked Questions (FAQs) About Emergency Heat
Is Emergency Heat Safe To Use?
Emergency heat is safe when used as directed by your system manual or technician. However, prolonged use can strain the electric elements and increase fire risk from overuse or faulty wiring, especially in older systems.
How Long Can I Run Emergency Heat?
Emergency heat is meant for temporary use—usually until a technician resolves the underlying issue. Extended use is expensive and may damage your heating equipment.
Does Emergency Heat Work During A Power Outage?
No—emergency heat requires electricity to operate electric coils or control the backup system. In a power outage, only homes with a generator or fuel-powered backup heater (and manual operation) will retain heating capability.
How Will I Know If My Home Needs Emergency Heat?
If your thermostat flashes a “Call For Emergency Heat” message, or your system cannot reach or maintain the set temperature, evaluate for possible mechanical failure, ice on the outdoor unit, or extremely low temperatures. When in doubt, consult an HVAC professional.
Will My Thermostat Automatically Switch To Emergency Heat?
No—most thermostats require you to manually engage emergency heat. They will, however, switch to auxiliary heat automatically as needed based on temperature differentials.
Upgrading And Maintaining Your Heat Pump For Reduced Emergency Heat Use
Proper system sizing and routine servicing are essential to minimizing emergency heat engagement. As heat pump technology advances, many US manufacturers now offer cold-climate models that function efficiently at temperatures as low as 5°F or below. Consider replacing older heat pumps with these options if you frequently rely on emergency heat.
Clean filters, regular coil inspections, and prompt repair of minor issues can significantly reduce your reliance on expensive, inefficient emergency heating.
Environmental Impact Of Emergency Heat
Electric emergency heat has a higher carbon footprint than standard heat pump operation, as it requires significantly more power. Utilizing it only when necessary, and for the briefest possible period, helps reduce household emissions and environmental impact.
What To Ask Your HVAC Technician About Emergency Heat
If you’re unsure about emergency heat settings or how your system handles backup heating, ask your technician the following:
- What type of backup heating is installed—electric, gas, or oil?
- How do I safely activate and deactivate emergency heat on my thermostat?
- What signs indicate a transition to emergency heat is necessary?
- What can I do to prevent emergency heat reliance in my specific home?
Comparing Heat Pumps With Emergency Heat To Other Heating Options
Heat pumps with emergency heat remain popular in the US because of their superior efficiency in mild to moderate climates. However, in frigid regions, dual-fuel systems—pairing a heat pump with a gas furnace—provide an automatic, efficient backup solution. These systems automatically switch to the optimal heating source based on temperature, outperforming electric resistance backups in severe weather.
| System Type | Primary Heat Source | Backup/Emergency | Efficiency |
|---|---|---|---|
| Standard Heat Pump | Outdoor compressor | Electric resistance | High (except emergency) |
| Dual-Fuel Heat Pump | Outdoor compressor | Natural gas furnace | Very high |
| Gas Furnace | Natural gas | N/A | Moderate (depends on efficiency) |
Tips For Home Comfort And Reduced Energy Costs
- Keep a close eye on your thermostat during bitterly cold weather to ensure your heat pump is still functioning.
- Have a contingency plan—portable heaters, extra blankets, and energy conservation strategies—for unforeseen outages or breakdowns.
- Consider enrolling in a maintenance program with your HVAC provider to ensure seasonal preparedness and reduce emergency heat occurrences.
Final Thoughts On Emergency Heat For American Households
Emergency heat on a heat pump is a safety net for your home comfort, not a primary tool for everyday heating. Understanding its purpose, costs, and proper usage ensures that your home remains warm and secure during extreme winter conditions without unnecessary expenses. When used as intended, emergency heat provides crucial backup protection. Staying proactive with home and equipment maintenance will keep your system running efficiently and limit the need to rely on this energy-intensive last resort.