Heat Pump Emergency Heat: When to Use It and How It Works

Heat pump emergency heat is a backup heating mode designed for situations when the primary heat pump cannot maintain indoor temperatures or is malfunctioning. This article explains what the emergency heat setting does, when to use it, how it affects energy bills, and steps homeowners should take to diagnose problems and restore normal operation. Readers will learn practical guidance for safe, efficient use and decision-making about repairs or replacements.

Topic	Key Point
What Emergency Heat Is	Backup electric or fossil-fuel heat activated manually or automatically
When To Use	Heat pump failure, extremely low outdoor temperatures, or defrost issues
Cost Impact	Higher energy use; significant increase in electric bills if electric strip heat used
Immediate Actions	Check thermostat mode, inspect outdoor unit, call a technician

What Is The Emergency Heat Setting?

The emergency heat setting is a secondary heating source integrated with many heat pump systems. It relies on electric resistance heaters (strip heat), a gas furnace, or another auxiliary heating method to produce warmth when the heat pump cannot extract sufficient heat from the outdoors.

Emergency heat should not be used as routine heating because it bypasses the heat pump’s efficient heat extraction process and uses more energy per unit of heat delivered.

How Heat Pumps Normally Heat

Heat pumps transfer heat from outdoor air into the home using a refrigerant cycle and a compressor. This process typically uses less electrical energy than direct electric resistance because it moves heat rather than generate it through electricity.

When outdoor temperatures are moderate, a heat pump operates efficiently, providing economical heating. The system switches between heating and defrost cycles automatically to maintain performance.

Why Emergency Heat Exists

Emergency heat protects comfort and safety. It is necessary when the heat pump is unable to operate properly due to mechanical failure, electrical faults, or extreme weather conditions that reduce heat pump efficiency beyond practical limits.

Common causes include compressor failure, refrigerant leaks, control board problems, failed reversing valves, or persistent outdoor ice that prevents effective heat exchange.

When To Use Emergency Heat

Emergency heat is appropriate in these situations: when the heat pump stops heating entirely, when the system cycles on and off abnormally, during long defrost cycles that leave the home cold, or when a technician advises using it while awaiting repairs.

It is also useful when outdoor temperatures drop below the manufacturer’s recommended balance point and the heat pump cannot maintain setpoint alone, though modern cold-climate heat pumps often extend that balance point lower.

When Not To Use Emergency Heat

Do not use emergency heat for regular operation. If the thermostat is set to emergency heat accidentally, it will run the auxiliary system continuously and cause much higher utility costs.

If the heat pump is operating normally or just recovering from a brief defrost cycle, the system should remain in standard heat mode instead of emergency heat.

How To Tell If Emergency Heat Is Active

The thermostat display typically shows “Emergency Heat,” “EM Heat,” or “Aux/E” when engaged. In some systems the thermostat will display an auxiliary heat icon or change the operating mode indicator.

If the thermostat reads emergency but no extra heat is felt, the auxiliary elements might be faulty; in that case, a professional inspection is warranted.

Energy And Cost Implications

Emergency heat operated by electric resistance heaters uses roughly three to four times more electricity per unit of heat than a functioning heat pump. This causes substantial increases in electric bills if used for extended periods.

If emergency heat uses a gas furnace as the backup, fuel costs will rise but may be less than electric resistance in some regions. Homeowners should compare local energy prices to understand the cost trade-offs.

Safety Considerations

Electric strip heaters generate significant heat and must have clearances to avoid fire risk. Thermostats and safety limits should be functioning to prevent overheating.

If unusual smells, sparks, or tripped breakers appear when emergency heat is engaged, turn off the system and call a licensed HVAC technician immediately.

Troubleshooting Steps Before Using Emergency Heat

Homeowners can perform simple checks before switching to emergency heat: verify thermostat settings, ensure the outdoor unit has power and is clear of debris, and confirm circuit breakers and fuses are intact.

Listen for the outdoor compressor; if it’s running but the house remains cold, wait through a typical defrost cycle before switching to emergency heat. If there is no compressor activity, emergency heat may be appropriate.

How To Switch To And From Emergency Heat

Most thermostats require manually selecting “Emergency Heat” or “EM Heat.” Some advanced systems or smart thermostats allow contractor programming that locks out emergency mode to prevent misuse.

After repairs or when the heat pump resumes normal operation, switch the thermostat back to “Heat” or “Auto” to restore efficient heating. Leave emergency mode off during mild weather.

Diagnosing Common Heat Pump Problems

If emergency heat is needed frequently, it indicates an underlying problem. Technicians typically inspect refrigerant levels, compressor function, reversing valve operation, contactors, and control boards.

Other common issues include clogged air filters, blocked outdoor coil, or thermostat calibration errors; many of these items are inexpensive to fix and restore heat pump efficiency.

When To Call A Technician

Contact a licensed HVAC professional when the compressor won’t run, there are electrical faults, refrigerant leaks suspected, or when repeated trips to emergency heat occur. Professionals can perform diagnostics, repair mechanical components, and test safety controls.

During service calls, homeowners should request a clear explanation of the problem, the estimated repair cost, and whether replacement is more cost effective than repair.

Maintenance To Reduce Emergency Heat Use

Regular preventive maintenance lowers the chance of emergency heat activation. Recommended tasks include replacing filters every 1–3 months, clearing debris from outdoor units, and scheduling annual professional tune-ups.

During tune-ups, technicians should check refrigerant charge, electrical connections, and thermostat calibration to ensure reliable heating performance and energy efficiency.

Upgrades And Alternatives

Homeowners considering frequent emergency heat use may evaluate upgrading to a modern cold-climate heat pump that maintains efficiency at lower temperatures or installing a high-efficiency backup furnace paired with smart controls.

Smart thermostats with diagnostics can detect anomalies early and reduce unnecessary switches to emergency heat. Incentives and rebates for high-efficiency heat pumps may be available through local utilities.

Practical Tips For Minimizing Costs While On Emergency Heat

When emergency heat runs, lower the thermostat a few degrees to reduce operating hours. Use zonal heating, close off rooms not in use, and improve insulation to retain warmth.

Consider supplemental measures such as electric space heaters for brief localized warmth, but use them safely and be mindful that combined electricity use can still be high.

What To Expect From Repairs Or Replacement

Repair scope varies from simple control board resets to compressor replacement. Compressor failures are among the most expensive repairs and may justify investing in a new unit if the system is older.

Aging heat pumps (10–15 years or older) may be less reliable and less efficient. Replacing with a modern, appropriately sized heat pump often yields long-term energy savings and reduced emergency heat incidents.

Using Thermostat Settings Correctly

Thermostats should be set to “Heat” or “Auto” for normal operation. Emergency settings are labeled to prevent confusion, and some systems include distinct “Aux heat” and “Emergency heat” options; homeowners should follow the manufacturer’s manual for specific guidance.

Training household members to avoid accidentally selecting emergency heat reduces the risk of unexpected high energy bills.

Frequently Asked Questions

Does Emergency Heat Turn On Automatically?

Most systems do not automatically switch to emergency heat unless configured to do so by a technician or as part of an integrated control strategy; manual activation is common on many thermostats.

How Much More Expensive Is Emergency Heat?

Electric resistance emergency heat can be 3–4 times more expensive per unit of heat delivered than a working heat pump. Exact costs depend on local electric rates and the duration of use.

Can Emergency Heat Damage The Heat Pump?

Using emergency heat itself does not harm the heat pump, but prolonged use without addressing the root cause can allow system components to deteriorate and increase repair urgency.

Is Emergency Heat The Same As Auxiliary Heat?

Emergency heat and auxiliary heat are related but not identical. Auxiliary heat often engages automatically to support the heat pump when needed; emergency heat is a manual override used when the primary heat pump is out of service.

Key Takeaways And Best Practices

Use emergency heat only when necessary, verify thermostat settings, perform simple pre-checks, and schedule professional service promptly if heat pump performance is compromised.

Maintain the system with regular inspections and consider modern heat pump upgrades if emergency heat use is frequent. These steps preserve comfort, safety, and energy efficiency while preventing costly utility bills.

For immediate issues, homeowners should switch to emergency heat temporarily, lower the thermostat to save energy, and contact a licensed HVAC technician for diagnosis and repair.