Not all heat pumps have emergency heat built in, but most modern systems do include it as a backup when outdoor temperatures drop
Emergency heat—also called auxiliary heat or backup heat—is an electric resistance heating element that kicks in when your heat pump cannot pull enough warmth from the outside air. Whether your system has it depends on the type of heat pump you own and when it was installed. Older heat pumps, ductless mini-split systems, and some budget models may not have it. If your heat pump does have emergency heat, you control it through your thermostat, usually with a switch labeled "Emergency Heat," "Aux Heat," or "E Heat."
The reason emergency heat exists is practical: heat pumps become less efficient as outdoor temperature drops, and below a certain point—usually around 35°F to 40°F depending on the model—they struggle to heat your home fast enough. Emergency heat uses electric resistance (like a space heater) to make up the difference. It costs more to run than the heat pump itself, so it is meant to be a temporary solution, not your primary heating method.
Key Takeaways
- Most air-source heat pumps installed in the last 15 years include emergency heat, but ground-source heat pumps and ductless mini-splits often do not.
- Emergency heat activates automatically on many systems when outdoor temperature drops below the balance point, usually 35°F to 40°F.
- You can manually switch to emergency heat mode on your thermostat if the heat pump is running but not keeping up, though this should be temporary.
- Emergency heat uses electric resistance and costs roughly two to three times more per hour to run than your heat pump alone.
- If your heat pump does not have emergency heat and fails in winter, you will need a portable heater or to call a technician when ready.
Which heat pump types include emergency heat
Air-source heat pumps—the most common type in residential homes—almost always include emergency heat if they were installed after 2010. The backup element sits in the indoor air handler or furnace and activates when needed. Older air-source systems may not have it; if you own a heat pump installed before 2005, check your thermostat or manual to confirm.
Ground-source (geothermal) heat pumps rarely need emergency heat because the ground stays a constant temperature year-round, so the system can heat efficiently even in cold weather. Most geothermal installations do not include a backup element, and if they do, it is rarely used.
Ductless mini-split heat pumps typically do not have emergency heat. Each indoor unit heats independently, and there is no central location for a backup element. If a mini-split fails in winter, you lose heat in that zone until it is repaired.
Hybrid systems—a heat pump paired with a gas furnace—use the furnace as the backup instead of electric resistance. The system automatically switches to the furnace when the heat pump cannot keep up, which is more efficient than electric emergency heat.
How emergency heat activates on your thermostat
Most modern thermostats have a switch or setting for emergency heat, though the label varies. Look for "Emergency Heat," "Aux Heat," "E Heat," or sometimes "Backup Heat." On a programmable or smart thermostat, this is usually a mode you select alongside "Heat," "Cool," and "Auto."
On many systems, emergency heat activates automatically when the outdoor temperature drops below your heat pump's balance point. The balance point is the temperature at which your heat pump alone cannot meet your heating demand, so the system turns on the backup element without you doing anything. You will see this reflected on your thermostat display—it may show "Heat" and "Aux" running together, or it may straightforward show "Heating" without specifying which source.
You can also manually switch to emergency heat mode by flipping the thermostat switch. This forces the backup element to run instead of the heat pump. Homeowners sometimes do this if the heat pump is running but the house is not warming fast enough, though this should only be temporary because emergency heat is expensive to operate.
When emergency heat turns on and off
Automatic emergency heat set up depends on your thermostat settings and the outdoor temperature sensor. Most systems are programmed to set up the backup element when outdoor temperature falls below 35°F to 40°F, though this varies by manufacturer and can sometimes be adjusted by a technician.
Once the outdoor temperature rises above that threshold, the backup element shuts off and the heat pump takes over again. If you manually switched to emergency heat mode, the system stays in that mode until you switch it back to "Heat" or "Auto"—it does not automatically revert. This is why it is important to remember to turn it off; leaving it on will run up your heating bill significantly.
Some smart thermostats and newer systems allow you to set custom balance points or schedules for emergency heat. If you have a programmable thermostat, your installer or the manual should explain how to adjust these settings. If you are unsure, contact your heat pump installer or a local HVAC technician.
The cost difference between heat pump and emergency heat
Running emergency heat costs roughly two to three times more per hour than running your heat pump alone, depending on your local electricity rates and your system's efficiency rating. This is because electric resistance heating converts electricity directly to heat with no efficiency gain, whereas a heat pump moves existing heat from outside and uses electricity only to power the compressor.
For example, if your heat pump costs $2 per hour to run, emergency heat might cost $5 to $6 per hour. Over a full winter, leaving emergency heat on continuously instead of using the heat pump could add hundreds of dollars to your electric bill. This is why emergency heat is designed as a backup for brief periods—a few hours on a very cold day, not a heating method for weeks.
If you find yourself using emergency heat frequently, it usually means your heat pump is undersized for your climate, your home is poorly insulated, or the system needs maintenance. Contact an HVAC technician to diagnose the issue.
What to do if your heat pump does not have emergency heat
If your heat pump fails during winter and you do not have emergency heat or a backup system, you will need temporary heating until a technician can repair it. A portable electric space heater can warm one or two rooms enough to stay safe and comfortable while you wait for service. Keep the heater at least 3 feet from curtains, furniture, and bedding, and never leave it running unattended.
If the repair will take more than a day or two, consider staying with family or friends, or renting a hotel room. A failed heat pump in freezing weather is a safety issue—pipes can freeze and burst, and prolonged cold indoors is a health risk, especially for children and elderly people.
To avoid this situation, have your heat pump serviced annually before winter arrives. A technician can check refrigerant levels, clean coils, and confirm that the system is running efficiently. Regular maintenance reduces the chance of a winter failure and ensures emergency heat (if you have it) will work when needed.
Frequently Asked Questions
Can I turn on emergency heat manually if my house is cold?
Yes, you can switch your thermostat to emergency heat mode if the heat pump is running but your home is not warming fast enough. However, this should only be temporary—a few hours at most—because it costs significantly more to operate. If you need emergency heat frequently, have a technician check whether your heat pump is sized correctly for your home and climate.
Does emergency heat turn on automatically in winter?
On most systems, yes. When outdoor temperature drops below your heat pump's balance point (usually 35°F to 40°F), the backup element activates automatically without you changing the thermostat. You will see both "Heat" and "Aux" running on your display. Once the temperature rises, the backup shuts off.
What should I do if my heat pump stops working in winter?
If you have emergency heat, switch to that mode to stay warm while you call a technician. If you do not have emergency heat, use a portable space heater to warm one or two rooms and contact an HVAC service when ready. A failed heat pump in freezing weather is urgent because of the risk of frozen pipes and health hazards.
Is emergency heat the same as a backup furnace?
No. Emergency heat is an electric resistance element built into your heat pump system. A backup furnace is a separate gas or oil heating system paired with a heat pump in a hybrid setup. Hybrid systems are more efficient because gas heat costs less to run than electric resistance, but they require a furnace and gas line.
How do I know if my heat pump has emergency heat?
Check your thermostat for a switch or mode labeled "Emergency Heat," "Aux Heat," or "E Heat." If you do not see one, look at your system's manual or call your installer. You can also ask an HVAC technician during your next service visit—they can confirm whether your system has a backup element and show you how to use it.