Most homeowners see “EM Heat” on their thermostat and feel unsure about what it means. The thermostat setting seems simple, but its function is important. It affects how your heat pump works in cold weather and during equipment problems. EM Heat connects to your backup heating system and steps in when your main heat pump cannot keep up. This guide explains what EM Heat is, how it works, when to use it, and what signs tell you that your heat pump needs service.
What Is EM Heat? (Simple Definition)
EM Heat is your heat pump’s backup heat source that turns on when the system cannot produce enough heat. The emergency heat setting bypasses the outdoor unit and switches the load to your indoor heater. That heater can be an electric heat strip, gas furnace, oil system, or hot water coil.
A heat pump usually keeps your home warm on its own, but EM Heat steps up when the heat pump cannot do the job. The thermostat setting exists to give you a direct way to activate the backup heater when needed.
How EM Heat Works in a Heat Pump System
A heat pump works by pulling heat from outdoor air and moving it inside. It works well until the air outside drops below what the system can handle. When the outdoor air is too cold or the heat pump stops working, the backup heating system takes over. You see EM Heat on the thermostat when you use the backup heater manually. The system uses more electricity while EM Heat runs because it pulls heat from an indoor heating source instead of outdoor air.
EM Heat vs Auxiliary Heat (What’s the Difference?)
Many people think EM Heat and Aux Heat mean the same thing. They use the same secondary heating source, but the difference sits in how they start.
- Auxiliary heating turns on automatically when the heat pump needs support.
- EM Heat turns on only when you activate it manually.
Both rely on the same backup heater. The difference is the trigger. EM Heat is not for daily use, and the thermostat will not switch to EM Heat on its own. You must choose to switch to EM Heat.
When Should You Turn On EM Heat?
A few situations call for it. These moments are rare, but when they show up, the EM Heat setting helps you keep your home warm.
1. Heat Pump Failure
If the outdoor unit freezes over, shuts down, or stops heating, EM Heat keeps the house warm until repairs. You can activate it if your house feels cold and the outdoor unit does not run in heating mode.
2. Extreme Outdoor Temperatures
North Texas can drop into extremely cold weather during sudden cold fronts. When the temperature dips too low, the heat pump struggles to pull heat from the air. EM Heat fills the gap.
3. Waiting for Service
If your heat pump stops heating your home, EM Heat prevents the temperature from dropping while you wait for an HVAC technician. It keeps the house comfortable until someone can fix the main system.
When You Should NOT Use EM Heat
The emergency heat setting uses far more electricity than normal heat pump operation. It is not meant for everyday use.
You should avoid EM Heat in these situations:
- Normal cold days
- Testing the thermostat
- Trying to heat the home faster
- Mild winter temperatures
EM Heat draws power from resistance heat or a gas furnace. That means higher energy bills if it runs too long. Short bursts are fine. Long stretches cost money and usually point to a problem that needs repair.
Why EM Heat Costs More to Run
The reason is simple. Backup heat strips draw high electrical loads. When the heat pump stops using outdoor air and switches to the secondary heating system, your efficiency drops. The heat pump uses outdoor air most of the time because the process saves energy. EM Heat breaks that pattern. The cycle runs longer and burns more energy. You notice the difference when the utility bill arrives.
Signs Your Heat Pump Needs Service if EM Heat Stays On
EM Heat helps you when needed, but it should not stay on for long. If it does, your heat pump systems may need repair.
Watch for these signs:
- EM Heat stays on for hours
- Outdoor unit does not run during heating mode
- System blows lukewarm air
- Ice buildup forms on the outdoor coil
- Loud noises during heat mode
- Burning smell near the air handler
- Thermostat switches to Aux or EM Heat often
Any of these signs point to heat pump trouble. They show that the emergency heat is meant to help you, but the main system is struggling.
How to Turn EM Heat On and Off on Your Thermostat
Switching to EM Heat takes only a moment.
- Open your thermostat menu.
- Select Heat mode.
- Tap the EM Heat or Emergency Heat option.
- Switch back to normal Heat mode when you no longer need the backup heater.
Different brands show the setting in different places, but the action is the same. EM Heat sits as a manual override that you can turn on or off.
FAQ
Is EM Heat the same as Auxiliary Heat?
No. Aux Heat turns on automatically. EM Heat requires you to activate it manually.
Why does my thermostat show EM Heat?
Your heat pump needs support or the outdoor unit cannot heat your home.
Is it safe to use EM Heat?
Yes. It is safe for short periods. It costs more to run long-term.
Does EM Heat mean my heat pump is broken?
Not always. Cold air can trigger the need for backup heat. If EM Heat stays on, your heat pump may need service.
Should EM Heat run all the time?
No. Long EM Heat cycles suggest a problem with your heat pump.
How long can I run EM Heat safely?
You can run it for several hours. It is not ideal for days.
Can I ignore EM Heat warnings?
No. These warnings usually point to an issue in the heating system.
Keep Your Home Warm — Call Comfort Experts for Heat Pump Service
Heat pump problems don’t fix themselves, and EM Heat can drain your energy bill fast. Comfort Experts can diagnose the issue, restore your system’s normal heating mode, and replace failing equipment when needed. Homeowners across Fort Worth rely on us for fast, accurate heat pump service.
