Emergency heat, often labeled as Em Heat, is a thermostat setting designed for heat pumps that provides a backup heating source when the primary system cannot meet heating demands. This guide explains what Em Heat is, how it works, when to use it, and how it affects energy use and comfort. It aims to help homeowners in the United States make informed decisions about when Em Heat is appropriate and how to operate it safely and efficiently.
What Em Heat Is and How It Works
Em Heat, short for emergency heat, is a mode on many heat pump systems that switches the system to a conventional electric resistance heat source, often elements in the air handler, to produce heat quickly. In this mode, the heat pump’s outdoor unit may effectively be bypassed, and the backup heat source carries the load. This mode is intended for temporary use during extreme cold or when the heat pump is not functioning properly.
Key points to understand:
- Backup heating source activates when Em Heat is engaged, typically electric resistance coils inside the unit.
- Faster heat delivery tends to raise indoor temperatures quickly compared to the heat pump alone in cold weather.
- High energy consumption because electric resistance heat is less efficient than the heat pump in most conditions.
When to Use Em Heat
Em Heat should be reserved for specific scenarios and not used as a default setting. Common appropriate circumstances include:
- Outdoor temperatures are very cold and the heat pump struggles to meet demand.
- The heat pump is undergoing defrost cycles or is temporarily malfunctioning.
- Emergency situations where rapid warming is necessary and other options are unavailable.
Using Em Heat in normal weather can lead to higher energy bills without meaningful improvement in comfort. If the thermostat switches to Em Heat frequently, it may indicate a longer-term problem with the heat pump or the system’s refrigerant charge.
Energy Use and Cost Implications
Electric resistance heating, which Em Heat relies on, consumes electricity at a higher rate than the heat pump’s normal operating mode. This typically results in a noticeable increase in energy bills during the period Em Heat is active. Homeowners should monitor usage and use Em Heat only as needed to avoid unnecessary costs.
Consider these considerations for energy impact:
- Efficiency comparison Between heat pump operation and electric resistance heat varies with outdoor temperature; the heat pump is most efficient above four to five degrees Fahrenheit. As it drops below that range, resistance heat may be engaged to maintain comfort.
- Thermostat feedback Some thermostats display an estimated cost or runtime for Em Heat, assisting homeowners in making smarter choices.
- Long-term costs Prolonged use of Em Heat can dramatically increase annual energy consumption, especially in colder climates.
How To Turn Em Heat On Or Off
Most modern thermostats label the mode clearly as “Em Heat” or “Emergency Heat.” The exact steps can vary by brand, but the general process is similar:
- Access the thermostat menu and locate the heat mode options.
- Select Em Heat or Emergency Heat.
- To revert, choose Heat or Auto depending on the thermostat’s terminology.
Brand-specific tips:
- Wi-Fi connected thermostats often provide energy usage insights and notifications if Em Heat remains active too long.
- Learning thermostats may adjust schedules to minimize Em Heat usage once the system confirms a stable operation.
- If you are unsure, consult the user manual or contact a licensed HVAC technician for personalized guidance.
Common Signs Em Heat Is Active
Recognizing Em Heat can prevent energy waste and help diagnose equipment issues:
- Rapid, immediate warmth with high electricity draw.
- Thermostat indicates “Em Heat” on its display.
- Outside temperature is very low and the indoor air feels warm to mild despite long cycle times.
- Unexpectedly high energy bills during a cold stretch.
Note that some systems may show “Auxiliary” or “Aux” heat, which is a related but distinct function used in conjunction with the heat pump. Em Heat is specifically the emergency backup mode.
Em Heat vs. Auxiliary Heat: A Quick Comparison
| Feature | Em Heat | Auxiliary Heat |
|---|---|---|
| Primary purpose | Backup heating when heat pump can’t meet demand | |
| Activation mode | Engaged manually or automatically during extreme cold | |
| Energy use | High (electric resistance) | |
| Typical use case | Short-term emergency or extreme weather | |
| Impact on bill | Can be significant if used long |
Troubleshooting: Is Em Heat Supposed To Be Running?
If Em Heat runs more than expected, consider these checks:
- Thermostat programming Ensure the thermostat is not stuck in Em Heat due to a schedule error.
- Heat pump performance If the outdoor unit is blocked by snow or debris, efficiency drops and Em Heat may engage more often.
- Refrigerant levels Low refrigerant can impair heat pump efficiency, increasing reliance on Em Heat. This requires a licensed technician.
- Airflow issues Blocked filters or restricted ductwork reduce heating efficiency and may trigger Em Heat.
If there is any doubt about system safety or efficiency, contact a licensed HVAC professional for a diagnostic check and maintenance.
Safety, Maintenance, and Best Practices
To maximize comfort and minimize risk when Em Heat is used, follow these best practices:
- Schedule regular maintenance to keep the heat pump and backup heating elements in good condition.
- Replace air filters regularly to ensure proper airflow and efficiency.
- Keep outdoor unit clear of snow, leaves, and debris to maintain performance during cold snaps.
- Monitor usage review energy consumption reports from smart thermostats to determine whether Em Heat is being used excessively.
- Understand your equipment Know whether your system uses electric resistance heat and what the thermostat displays. This helps interpret Em Heat indications accurately.
Practical Scenarios: How Homeowners Can Use Em Heat Wisely
In very cold climates, Em Heat can be a useful safeguard on unusually frigid days. For instance, during a polar cold snap, Em Heat may protect indoor comfort if the heat pump cannot keep up. After a storm or power restoration, Em Heat can help reestablish warmth quickly while the heat pump rebalances. In milder weather, rely on the heat pump’s standard operation to conserve energy.
Key takeaway: Em Heat is intended as a temporary, emergency backup, not a daily setting. Understanding its role helps balance comfort and energy costs while maintaining system reliability.