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Choosing the “EM Heat” option on your Honeywell thermostat turns on your secondary or auxiliary heating system, greatly speeding up the heating process in your living space.

This helps optimize for large temperature differences but it’s not recommended for continuous use. 

So if you’re wondering about “EM Heat” mode and when it's best to activate it, this article will show you how. 

What is Honeywell Thermostat EM Heat?

Emergency heat (often referred to as “EM heat” or “auxiliary heat”) is a backup heating option available in HVAC systems that typically rely on a heat pump as a primary heating source.

  • Typically, it is reserved for situations when your primary heating system fails or cannot provide sufficient warmth during extremely cold weather.
  • Utilizing the Honeywell thermostat EM heat ensures your home stays warm and comfortable even when your main heating mode is compromised, preventing potential damage caused by low temperatures.
  • When you activate the EM heat setting on your Honeywell thermostat, you disable the primary heating mode, which could be a heat pump, and switch to the auxiliary heating mode.
  • In certain models, the thermostat will automatically switch over to the auxiliary heating system whenever it senses that the outside temperature is too low for the heat pump to keep up.
  • This auxiliary mode relies on either an electric heat strip or a backup gas furnace to generate the needed warmth.
  • Although both these options will effectively heat your space, using the electric heat strip can significantly increase your energy consumption and result in higher electricity bills.
  • As such, EM heat should only be used as a temporary solution until the primary heating system is restored.

How to Switch Between Emergency Heat Mode and Other Modes

Depending on the model, the option to toggle the emergency heat may vary. So to address this, I’ve created a model-specific guide below. 

You can check these guides or head over to our collated list of Honeywell thermostat user manuals to browse the guide for your specific model.  

Honeywell Home App

Here's how to switch to emergency heat mode using the Honeywell Home App.

  1. Open the app on your smartphone or tablet.
  2. After that, browse through the app to locate and select your specific thermostat.
  3. Tap the “Mode” button located at the bottom right of the screen.
  4. Look for “EM Heat” or “Emergency Heat” among the mode options and select it.
  5. Save changes by tapping on the “Save” button to enable Emergency Heat on your Honeywell thermostat.
honeywell thermostat em heat
Changing temperature mode on the Honeywell Home app

T10 Pro and T9 Models

Smart thermostat with a color touchscreen

T9 1

For the recent T9 and T10 Pro models:

  1. Wake up the thermostat display by touching on it
  2. Then, access the main menu by pressing the three horizontal lines icon at the bottom of the home screen.
  3. Once you’re in the main menu, you will see various system modes options such as Heat, Off, Cool, Auto, and EM Heat.
  4. If you can’t find EM Heat, scroll down, it’s usually at the end of the list.

However, please note that certain models or HVAC systems won’t always offer the emergency heat setting.

Honeywell Home app showing the changing of modes
Changing the temperature mode on a Honeywell T10-style thermostat

T4, T5 and T6 Models

Smart thermostat with touchscreen

Honeywell Thermostats

For this set of models, the thermostat home screen displays the current system mode at the left of the indoor temperature. Therefore, you can switch between available modes by pressing on the “Mode” button 

How to change the mode on the Honeywell T4, T5 and T6 models
How to change the temperature mode on Honeywell T6 style thermostats

9000 and VisioPRO 8000 Series

Programmable thermostat with touchscreen

90008000 series all 1 2

To set your Honeywell thermostat's system mode for 9000 and 8000 models, follow these steps: 

  1. First, tap the “SYSTEM” button to display the different system settings.
  2. Then, choose the desired mode by tapping the corresponding option:
  3. Tap “Done” to save your selection and exit the settings.

Keep in mind that the Automatic and Emergency Heat settings might not be displayed, depending on your thermostat's installation.

9000 series change mode
Switching temperature modes on a 9000 series style thermostat

5000 and 6000 Series

Programmable thermostats

FocusPRO 6000 Series 1 4

For these programmable models, simply press the “SYSTEM” button to cycle through the available options.

5000 series change mode
Switching between different temperature modes on Honeywell 5000/6000 thermostats

4000 to 1000 Series

Programmable and Non-programmable thermostats

40002000 models 2

For these older models, you can toggle the available options using the physical switch located on the panel. In most models, this switch is at the bottom but can also be found on the side of the panel.

4000 series change mode
Switching temperature mode on older Honeywell thermostats

Similar Questions

When Should I Switch to EM Heat?

Setting the EM Heat on your Honeywell thermostat correctly can significantly improve your home's heating efficiency during cold snaps. Switch to EM Heat when your primary heat pump fails or cannot provide enough warmth. This usually happens during extremely cold weather (less than 30 degrees fahrenheit) or due to a damaged heat pump.

As such, it’s best reserved for true emergencies such as when the heat pump is damaged or nonresponsive.

In certain models, the thermostat will automatically make the switch. 

What Do I Need to Enable the EM Heat Function?

To enable the EM Heat function, your thermostat must be configured for a heat pump with backup heat. 

An installer will usually know how to make this configuration but you can also do this yourself in certain models with the help of the installation manual.

Also, the auxiliary heat pump's signal wire must be connected to the thermostat's wiring.

Doesn't Auto Mode Switch Over to EM Heat When Necessary?

Some thermostat models with the Auto Changeover feature can automatically switch to EM Heat when necessary. 

However, you still need to have the auxiliary heat sources (such as a gas furnace or heat strip) set up and wired correctly.

Is The Emergency Heat Setting More Expensive to Run?

Yes, emergency heat can be considerably more expensive than using the primary heat pump.

The cost difference depends on the heat source (such as gas furnaces or electric heat strips) and the duration of use.

Since it's pricier, I recommend you use the emergency heat setting sparingly and reach out to a professional technician to restore the regular heat pump functions as soon as possible.


The emergency heat mode setting on a Honeywell thermostat will power on the auxiliary heating system.  If you're experiencing issues with EM heat, you might also want to check why your Honeywell thermostat is flashing cool on.

As the name suggests, it’s reserved for extreme temperature changes or when the heat pump stops responding.

You can check the guides above to learn how to toggle this setting for different models. If you're experiencing issues with EM heat, learn more about troubleshooting a Honeywell thermostat not working on our detailed guide.


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