What is EM Heat
If you’ve ever looked at your thermostat and noticed a setting labeled “EM Heat” or “Emergency Heat,” you might have wondered what it means — and when you should use it.
In most homes across San Mateo, CA, especially those with heat pump systems, the Emergency Heat setting plays an important role during very cold weather or system malfunctions. But using it at the wrong time can lead to high energy bills and unnecessary wear on your system.
In this article, the experts at Cloud Mechanical HVAC explain what EM Heat is, how it works, when to use it, and what to do if it turns on automatically.
What Is EM Heat?EM Heat stands for Emergency Heat — a backup heating mode found on thermostats that control heat pump systems.
A heat pump normally works by transferring heat between the inside and outside of your home. But when outdoor temperatures drop too low (usually below 35–40°F), the heat pump can struggle to absorb enough warmth from the air.
When this happens, your system automatically or manually switches to Emergency Heat, which uses a secondary heating source (like electric resistance coils, gas, or oil) to maintain indoor comfort.
How EM Heat Works in a Heat Pump SystemTo understand EM Heat, it helps to know how a heat pump operates in heating mode:
When Should You Use EM Heat?You should only use EM Heat manually when your heat pump isn’t working properly.
For example:
In San Mateo’s mild winters, EM Heat is rarely needed — but it’s a useful backup for unexpected cold snaps or system malfunctions.
How to Turn On EM HeatIf your thermostat has an “EM Heat” option, here’s how to activate it safely:
How Much Does EM Heat Cost to Run?Emergency Heat can be 2–3 times more expensive to operate than a regular heat pump.
Here’s why:
5 Common Reasons EM Heat Turns On AutomaticallyYour system may switch to EM Heat automatically for several reasons:
Should You Leave EM Heat On All the Time?No — EM Heat is a temporary heating solution. Leaving it on for extended periods can:
How Cloud Mechanical HVAC Can HelpAt Cloud Mechanical HVAC, we provide heat pump repair, maintenance, and thermostat diagnostics for homeowners throughout San Mateo and the Bay Area.
If your system is stuck in Emergency Heat mode or isn’t heating efficiently, our licensed HVAC experts can:
✅ Inspect your heat pump and thermostat
✅ Repair refrigerant or electrical issues
✅ Restore normal operation
✅ Optimize your heating efficiency
🔥 Stay warm and energy-efficient — contact Cloud Mechanical HVAC today at (650) [insert number] or visit www.cloudmechanicalhvac.com to schedule a service appointment.
FAQs on Emergency Heat1. What does EM Heat mean on my thermostat?EM Heat stands for Emergency Heat — a backup heating mode used when your heat pump can’t function properly or during extremely cold weather.
2. Should I use EM Heat instead of regular heat?No. Only use EM Heat if your outdoor heat pump is malfunctioning or frozen. It’s much less efficient than normal heat pump operation.
3. Why is my EM Heat light on?The light means your system is running on backup heat. If you didn’t turn it on, your system may have a problem — contact an HVAC technician for inspection.
4. How much does it cost to run EM Heat?Running EM Heat can cost two to three times more than regular heating because it relies on electric resistance coils instead of heat transfer.
5. How do I turn EM Heat off?Simply switch your thermostat back to HEAT mode. If the light stays on, it may indicate a fault with the outdoor unit or thermostat.
In most homes across San Mateo, CA, especially those with heat pump systems, the Emergency Heat setting plays an important role during very cold weather or system malfunctions. But using it at the wrong time can lead to high energy bills and unnecessary wear on your system.
In this article, the experts at Cloud Mechanical HVAC explain what EM Heat is, how it works, when to use it, and what to do if it turns on automatically.
What Is EM Heat?EM Heat stands for Emergency Heat — a backup heating mode found on thermostats that control heat pump systems.
A heat pump normally works by transferring heat between the inside and outside of your home. But when outdoor temperatures drop too low (usually below 35–40°F), the heat pump can struggle to absorb enough warmth from the air.
When this happens, your system automatically or manually switches to Emergency Heat, which uses a secondary heating source (like electric resistance coils, gas, or oil) to maintain indoor comfort.
How EM Heat Works in a Heat Pump SystemTo understand EM Heat, it helps to know how a heat pump operates in heating mode:
- Normal Operation:
The heat pump extracts heat from the outdoor air and transfers it indoors. This is very energy-efficient because it moves heat rather than creating it. - Backup or Auxiliary Heat:
When it’s very cold outside, your system may automatically use auxiliary heat to assist the heat pump. This happens without you switching to EM Heat manually. - Emergency Heat Mode:
If your outdoor heat pump fails or freezes over, Emergency Heat takes over completely. It bypasses the outdoor unit and relies solely on your backup heating system, typically electric resistance coils or a furnace.
When Should You Use EM Heat?You should only use EM Heat manually when your heat pump isn’t working properly.
For example:
- The outdoor unit is damaged, frozen, or not running.
- The heat pump compressor fails.
- There’s a refrigerant leak or electrical problem preventing the system from heating.
In San Mateo’s mild winters, EM Heat is rarely needed — but it’s a useful backup for unexpected cold snaps or system malfunctions.
How to Turn On EM HeatIf your thermostat has an “EM Heat” option, here’s how to activate it safely:
- Set the thermostat to HEAT mode.
- Select EM HEAT (Emergency Heat).
- Adjust the temperature to your desired setting.
How Much Does EM Heat Cost to Run?Emergency Heat can be 2–3 times more expensive to operate than a regular heat pump.
Here’s why:
- A heat pump moves heat using electricity, requiring relatively little energy.
- Electric resistance heat (used in EM mode) creates heat by converting electricity directly into warmth — which uses much more power.
5 Common Reasons EM Heat Turns On AutomaticallyYour system may switch to EM Heat automatically for several reasons:
- Outdoor unit frozen or iced over
- Refrigerant leak or low pressure
- Thermostat malfunction
- Compressor or reversing valve failure
- Severe cold weather (rare in San Mateo)
Should You Leave EM Heat On All the Time?No — EM Heat is a temporary heating solution. Leaving it on for extended periods can:
- Triple your electricity consumption
- Cause higher utility bills
- Overwork your backup heating elements
How Cloud Mechanical HVAC Can HelpAt Cloud Mechanical HVAC, we provide heat pump repair, maintenance, and thermostat diagnostics for homeowners throughout San Mateo and the Bay Area.
If your system is stuck in Emergency Heat mode or isn’t heating efficiently, our licensed HVAC experts can:
✅ Inspect your heat pump and thermostat
✅ Repair refrigerant or electrical issues
✅ Restore normal operation
✅ Optimize your heating efficiency
🔥 Stay warm and energy-efficient — contact Cloud Mechanical HVAC today at (650) [insert number] or visit www.cloudmechanicalhvac.com to schedule a service appointment.
FAQs on Emergency Heat1. What does EM Heat mean on my thermostat?EM Heat stands for Emergency Heat — a backup heating mode used when your heat pump can’t function properly or during extremely cold weather.
2. Should I use EM Heat instead of regular heat?No. Only use EM Heat if your outdoor heat pump is malfunctioning or frozen. It’s much less efficient than normal heat pump operation.
3. Why is my EM Heat light on?The light means your system is running on backup heat. If you didn’t turn it on, your system may have a problem — contact an HVAC technician for inspection.
4. How much does it cost to run EM Heat?Running EM Heat can cost two to three times more than regular heating because it relies on electric resistance coils instead of heat transfer.
5. How do I turn EM Heat off?Simply switch your thermostat back to HEAT mode. If the light stays on, it may indicate a fault with the outdoor unit or thermostat.