Emergency Mode Activation: When Does A Heat Pump Switch?

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By Debarghya Roy

Heat pumps are a great way to keep your home comfortable year-round, but there can be times when switching to emergency heat is necessary. 

In this blog, we will explore what causes a heat pump to switch into emergency heat mode, common issues associated with it, and tips on how to optimize its usage in order to prevent damage.

Key Takeaways

  • Heat pumps are an energy-efficient way to heat and cool a home, but they may switch on emergency heat in certain situations.
  • Extreme cold temperatures, incorrect sizing for the climate, damage to components inside the compressor unit, freezing rain, and total system failure can cause a heat pump to trigger emergency heat.
  • Activation of emergency heat can be done manually or automatically depending on the system – owners should know what type of thermostat is installed before making any changes.
  • Use of this feature will draw more energy than regular operation which could lead to higher bills; homeowners should check filters regularly and keep thermostats lower than normal while it is engaged.

How Does Heat Pump Work?

Heat pumps are an energy-efficient way to heat and cool a home. In simple terms, they work by transferring the existing heat from outside to inside during winter.

when does a heat pump switch to emergency heat

This means that they don’t burn any fuel or create new heat, just transfer what’s already there.

The two main components of a heat pump are an indoor air handler unit and an outdoor compressor unit. 

The indoor air handler draws in warm air from the outside through the compressor unit, then passes it through evaporator coils which absorb all the warmth before pushing it back into your house or business as warm air via ducts or vents.

In more technical terms, when temperatures drop below freezing point (approx 0°C/32°F), refrigerant gas (often known as “Freon”) is injected into two sets of coils in the unit: one set outside and one set inside.

Heat energy transfers from outdoors to indoors where it heats up these coils slowly raising temperature levels until your thermostat has reached its target temperature setting for that time period.

What is emergency heat in a heat pump?

Emergency heat is an extra heating source used as a backup when the primary power source isn’t able to keep up with temperature requirements. 

Emergency heat will kick in if the ambient temperatures drop lower than what the set point on the thermostat specifies.

How Does A Heat Pump Switch To Emergency Heat?

When temperatures fall below a certain level, the heat pump will automatically switch to emergency heat mode in order to keep up with primary heating demands.

Factors That Trigger Emergency Heat

A heat pump’s emergency heat setting is activated under certain situations that put the system outside of its normal operating range. 

This typically occurs when the temperature outdoors drops below a specified threshold or if something happens to damage the heat pump itself. 

In such cases, it triggers an automatic switch to emergency heat in order to keep temperatures comfortable inside the home and prevent costly repairs.

Specifically, some common causes of emergency heat being engaged include:

  • Extreme cold weather with temperatures dropping below 40°F
  • Heat pumps not properly sized for colder climates
  • Damage occurring to parts inside of the compressor unit (such as defective coils)
  • Freezing rain causing blockage within external components such as fan blades or refrigerant lines
  • Total system failure due to mechanical issues within either indoor or outdoor units

Automatic Or Manual Activation Of Emergency Heat In Heat Pump

When it comes to heat pumps and emergency heat, deciding when to switch from the regular setting to emergency can be tricky. 

Depending on the system you have, your choice of activation will come down to either manual or automatic mode.

Manual activationAutomatic activation
DescriptionManual activation requires you to manually engage the setting on your thermostat at a predetermined time.Automatic activation will determine when it is necessary for the switchover by monitoring outdoor temperatures and other factors.
FeaturesOther models may require manual selection of no more than two stages of primary and second-stage heating combined with a third stage (emergency) setting if needed.Some systems, such as those with a Nest Thermostat.An auxiliary heating feature may automatically provide additional or secondary heating sources through electric resistance without switching to full-on emergency heat mode.

Energy Efficiency Considerations

When using a heat pump’s emergency heat setting, it is important to be aware of potential increases in energy consumption and costs

Switching to an electric resistance heating or furnace for backup can lead to higher utility bills due to the more significant amount of energy needed from these sources compared to when the primary heating unit is operating properly.

Therefore, homeowners should consider only activating their system’s emergency heat mode in extreme temperatures or when other problems have caused their regular source of heating to fail.

When To Switch From A Heat Pump To Emergency Heat?

It is generally recommended that a heat pump be switched to emergency heat when temperatures are extremely cold and the primary heating source is not efficient enough.

Extremely Low Temperatures

Extremely low temperatures can be damaging to a heat pump system. Heat pumps, which rely on air from outdoors to power its heating cycle, struggle in harsh winter weather with cold temperatures and strong winds.

As ice crystals form inside the unit, airflow decreases drastically, leading the outdoor coil’s temperature to drop severely below freezing. 

In such extreme conditions, a heat pump would start using more energy than it produces due to reduced efficiency as its ability to extract heat from outside air weakens considerably near or even below 0°F (-18°C).

This is when emergency heat kicks in: With this secondary source of heating activated manually or automatically as per your settings on thermostat keeping the system running for longer.

Emergency electric resistance strips will provide adequate BTU & raise indoor temperature immediately within a short span of time surpassing any lower limit measurements pre-set at the thermostat maintaining comfortable levels inside home—ideally in an all-electric setup above 45 °F (7 °C).

Heat Pump Malfunctions

Heat pump malfunctions can quickly trip the emergency heat setting, which activates a secondary heating source. 

  • This could be an electric strip or gas furnace depending on the model of your heat pump.
  • The most common causes of malfunction in heat pumps are freezing over and damages to the outdoor unit
  • Freezing occurs when temperatures drop too low for the outside unit to effectively transfer warm air indoors and ice builds up around it.

Common Issues With Heat Pump Emergency Heat

Heat pumps rarely run into problems with emergency heat, but when they do some common causes can be thermostat malfunctions, power outages, or clogged air filters.

Thermostat Malfunctions With Heat Pump Emergency Heat

can be one of the most common causes of problems with a heat pump system. It could be as simple as needing to replace the batteries, or it could indicate a bigger issue like wiring trouble or programming errors.

Inadequate maintenance, incorrect installation, and physical damage are some other possible reasons for thermostat malfunctions

A broken thermostat can prevent your heat pump from running efficiently which increases energy costs and reduces comfort levels in your home.

To ensure proper functioning of the system, it is important to inspect all parts regularly including the thermostat wires and programming settings. 

Issues such as frayed wiring that occurs due to age should be quickly taken care of by experienced technicians who specialize in this field.

Power Outages Of Heat Pump Emergency Heat

A power outage can be a major issue for heat pump owners if their homes lose primary heating during periods of extreme cold. 

If the electricity has been out for more than 30 minutes, it’s important to switch your thermostat’s setting from “heat” to “emergency heat” in order to avoid more extensive damage or repair costs.

While emergency heat is still not ideal as it tends to use more energy than regular operation, it acts as a secondary source of energy which will allow the system to remain heated until full power is restored.

In some cases where temperatures reach sub-zero levels for extended periods of time and the power has been off longer than an hour.

Refrigerant lines may become too cold and too thick for proper flow when you turn the system back on making switching your thermostat recommendable even prior to reaching the 30 minute mark in these events.

Clogged Air Filters With Heat Pump Emergency Heat

Clogged air filters can be an issue for heat pumps and, if left unattended, can cause the system to switch to emergency heat

This happens as dirty or clogged air filters reduce airflow to the heat pump, which decreases its efficiency and makes it run constantly in order to maintain the desired temperature.

When this takes place, it leads to an increase in energy consumption bills due to inefficient performance and the continuous use of supplemental heating sources needed when relying on emergency heat.

Troubleshooting Tips For Heat Pump Emergency Heat

It can help you fix or prevent potential issues with your heat pump emergency system.

Checking The Thermostat Settings

Regularly checking the thermostat settings ensures efficient and effective operation of your heat pump system. 

Here’s what you need to do to check:

Examine the display on your thermostat

Examine the display on your thermostat or owner’s manual for information about whether it has an emergency heat setting feature, as not all systems have this option.

Ensure that you can clearly read any text 

If required, adjust brightness levels using controls found on some models but not necessarily all. It’s also useful to be aware that many digital displays may only show 0/1 or ON/OFF for standby mode indication meaning further changes must be made if yesterday’s defaults are optimal today too.

Once located by pressing up

Press up the down buttons, and change settings directly from those numbered/labeled positions (e.g., 56°F) versus relying upon a “cooler hot warmer” indicator asking the user adjacent quick readings to confirm the understanding desired direction

Cut in the temperature range

On colder days make sure excess typically called cut in temperature range lowers (& vice versa when weather warms seasonal & insulation reduces infiltration) so that efficient mechanical sensing determines the availability of alternative energy sources.

Set ventilation fan speed carefully

Enable humidity where indicated once factors specific location mean attempts stop frost being blown into pipe needs ramp during large temperature drops

Inspecting The Outdoor Unit

It is important to check the outdoor unit of a heat pump for several reasons. 

The outdoor unit plays an important role in the heating system and should be checked regularly to ensure optimal performance. 

Failure to inspect and maintain the outdoor unit can cause premature failure or other issues such as power outages, insufficient heating capacity, inadequate cooling/heating cycles, clogged air filters, and improper defrosting.

Heat pump owners should take steps to ensure that their outdoor units are functioning properly:

  • Check for excess debris such as leaves or tree limbs on top of or around the unit.
  • These can interfere with proper flow of air through the condenser’s coils and impact its performance if not removed.
  • Ensure that there is sufficient room for proper airflow 
  • Schedule professional maintenance visits at least once per year in order to identify any underlying issues before they become more serious problems that could lead to costly repairs down the line.

Changing Air Filters

Regularly changing the air filters in your heat pump system is important since dirty or clogged filters reduce airflow to the system, affecting its efficiency and preventing it from running properly. 

When selecting an air filter for a heat pump, choose a standard pleated model with a MERV (Minimum Efficiency Reporting Value) rating of 11 or 12 which offers superior filtration while still allowing sufficient airflow.

To change out an air filter:

  • Shut off the power source before removing the old filter
  • Carefully remove the old filter from the frame
  • Measure the new filter exactly for the size
  • Check that arrows are going in the same direction of airflow when installing new one 
  • Reattach the faceplate securely after inserting the new air filter

How To Turn Off Emergency Heat On A Heat Pump?

To turn off emergency heat on a heat pump, you can either do it manually or use the auto deactivate feature.

Automatic Deactivation

Automatic deactivation of emergency heat is a feature found on many modern heat pump systems, which triggers when the temperature outside drops too low and the indoor air does not meet the desired set point.

This typically happens when temperatures drop below freezing or during times of extreme cold weather. 

When this occurs, the heat pump switches to what is known as its auxiliary heating mode also referred to as backup heating in order to keep homes warm while preserving energy efficiency.


  • The benefits of an automatic deactivation feature are that it can dramatically reduce utility costs by avoiding unnecessary use of emergency heat while increasing overall system efficiency.
  • It provides peace of mind for homeowners since they know their home will be kept comfortable even if there’s an unexpected deep freeze over a large area.

Manual Deactivation

In order to manually deactivate your heat pump’s emergency heat mode, you will need to access the thermostat

Before doing so, be certain to turn off any electricity sources going directly into the thermostat in order to prevent possible electric shock.

If you have a digital or programmable unit, locate and press the button with the “auto” symbol on it for several seconds until an indicator light flashes. 

It is also recommended that those who do not have automatic models make sure they do not leave their systems running without adjustment for longer periods of time.

Once a manual deactivation has been carried out successfully by locating and pressing the designated “off” button, users may then adjust their thermostat back to its normal functioning level or temperature setting 

If deemed necessary by using switches corresponding with fan speed (e.g., high and low) as well as heating/cooling modes or functions (e.g., heat pump versus auxiliary).

Benefits And Drawbacks Of Emergency Heat

Emergency heat can provide a backup source of heat in extreme cold conditions, but it can also be costly and inefficient.

Cost Considerations

Having to switch to emergency heat on a heat pump can significantly drive up energy costs as it switches the source of heat from the more efficient and inexpensive heat pump to an electric coil or electric strip, which are less efficient and much more expensive.

The Department of Energy estimates that you can save up to $1,000 per year by switching your home’s heater over from a gas furnace or oil-burning system to a modern air-source heat pump.

When using emergency heating during colder months, it is important not to use it necessarily when both stages of the heat pumps are working together; it should only typically be used in real emergencies such as thermostat malfunctions or power outages.

Additionally, if you find yourself constantly setting your thermostat into emergency mode consistently throughout cold weather, then there may be something wrong with your primary heating source that needs repair or servicing.

Environmental Impact

Using emergency heat on a heat pump can have both short and long-term negative impacts on energy efficiency and the environment. 

As emergency heat is generated by electric resistance heating, which involves major electrical output, this type of heating depletes substantial amounts of electricity in comparison to regular usage.

As such, using more electricity than necessary causes an increase in energy costs while simultaneously reducing overall efficiency.

Practically speaking, certain measures can be taken even before the need for emergency running with chillier climates ahead making sure your home remains at comfortable temperature levels all year round.

Making simple improvements like using LED lighting or replacing dirty air filters will help maintain optimal system performance and reduce overall operating costs; keeping out any object close to outdoor condenser units.

Repair And Maintenance Services  For Heat Pump Emergency Heat

When it comes to heat pumps, regular repair and maintenance is an important tool for ensuring the system operates at a high level of optimum performance. 

Working with trained professionals can help homeowners avoid problems which could lead to costly repairs or emergency situations. 

Well-maintained heat pumps will last longer, have lower energy costs, improved air quality in the home, and provide sufficient heating and cooling when needed.

Regular maintenance should include:

  • Inspecting all electrical connections for corrosion or damage
  • Checking thermostats for calibration accuracy
  • Cleaning outside coils and debris from the surrounding area
  • Testing fan motors, capacitors and contactors if necessary
  • Replacing air filters regularly
  • Monitoring refrigerant pressure levels throughout each season

Professional HVAC Services For Heat Pump Emergency Heat

When upgrading your home’s heating system or needing emergency heat services, experienced HVAC professionals can assist you in keeping your Heat Pump running safely and efficiently.

Professional tune-up 

A professional tune-up addresses any potential issues before they become problematic.

Allowing your system to operate efficiently with fewer breakdowns due to wear-and-tear malfunctioning parts that could end up costing you more money down the line if neglected too long without proper servicing. 

In addition, technicians also check safety features like interlock switches, safety control boxes, gas furnace drafts among other components annually. 

Upgrading existing systems through regular maintenance can reduce bills by 30%-50%, significantly reducing both environmental impact and energy consumption as well as providing cooler temperatures during hot weather months .

Emergency Assistance

Heat pump owners should be aware that a reliable and professional HVAC service provider is always available to assist with heat pump emergency heat issues.

Heat pumps rely on both indoor and outdoor units, as well as various electrical components and settings, in order to allocate correct temperatures throughout the house. 

A lack of regular maintenance or improperly working refurbished parts can lead to easy breakdowns when dealing with harsh winter weather.

Professional technicians have experience dealing with these kinds of emergencies, ensuring proper diagnosis and repair of any problems before they become major repairs.

This saves time, money, and energy efforts all around while providing a healthy supply of adequate heat during the cold season.


How can I tell when my heat pump is running on emergency heat?

You may notice that your bills are much higher than usual and also that it’s taking longer for your house to reach its desired temperature level, this would be an indication that your system has switched over to emergency heating mode, which typically happens during colder winter months when outdoor temperatures plunge below 0°C (32°F).

When does my Heat Pump switch back from Emergency Heat? 

Once outside conditions get closer to their consistent levels again or warmer, usually above 5C-7C (40-45 F), your furnace will automatically switch back from using only emergency heating sources and rely instead once more entirely upon regular operation of existing components.


Heat pump emergency heat is a necessary backup system to ensure that you and your family stay warm if the primary heating source fails. When it comes to optimizing emergency heat, there are several energy-efficient benefits as well as potential risks involved.

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