Updated July 29, 2026: Heat pump controls vary by manufacturer, thermostat, equipment type and backup-heating configuration. The terms AUX Heat, Backup Heat and Emergency Heat do not operate identically on every system. Follow the operating instructions for your specific equipment and have installer settings reviewed when system behaviour does not match the intended design.
AUX Heat and Emergency Heat are not the same thing. Auxiliary heat is supplementary heating that the system can call automatically when the heat pump needs help meeting the heating demand. Emergency Heat is a manual or control-driven backup-only mode available on many central heat pump systems and is generally intended for situations where normal heat-pump heating cannot be used.
In a common all-electric central system, AUX Heat may come from electric resistance heaters inside the air handler. During normal heating, the heat pump compressor can continue operating while electric auxiliary heat adds capacity.
On many thermostat-controlled systems, selecting Emergency Heat locks out normal compressor heating and relies on the backup heat source instead. If that backup is electric resistance heat, extended Emergency Heat operation can use considerably more electricity than ordinary heat-pump heating.
Seeing AUX Heat occasionally during cold weather, defrost or a large temperature recovery does not automatically mean something is wrong. Seeing it continuously during mild weather, or discovering that Emergency Heat has been left on unintentionally, deserves closer attention.
AUX Heat vs Emergency Heat: What Is the Difference?
| Feature | AUX Heat | Emergency Heat |
|---|---|---|
| How it starts | Usually automatic | Often manually selected or commanded during a fault condition |
| Main purpose | Add heat when the heat pump needs assistance | Provide backup heating when normal heat-pump heating should not be used |
| Heat pump compressor | May continue operating in an all-electric system | Commonly locked out on thermostat-controlled central systems |
| Possible heat source | Electric resistance, furnace, baseboards or another designed source | Backup heat source configured for the system |
| Normal during cold weather | Can be | Not normally a routine operating mode |
| Electricity use | Can increase significantly when resistance heat is used | Can be high when the backup source is electric resistance |
| Homeowner action | Usually allow normal automatic control | Use according to equipment instructions or when normal heat-pump operation is unavailable |
The exact behaviour depends on the thermostat and heating-system design.
Think of AUX Heat as Assistance
The heat pump is still the primary heating system in a typical all-electric installation, while supplementary heating adds capacity when necessary.
Think of Emergency Heat as Backup-Only Operation
On many central heat pump thermostats, Emergency Heat prevents the compressor from providing normal heating and relies on the configured backup source.
That makes Emergency Heat useful during certain failures, but generally a poor choice for everyday operation when the heat pump is working normally.
What Can Provide Heat Pump Backup Heating?
Backup or supplementary heat does not always mean electric heat strips.
Electric Resistance Heat
A central air handler can contain electric resistance heaters.
They may provide:
- Auxiliary heat
- Defrost support
- Emergency heating
Gas Furnace
In a dual-fuel system, a natural gas furnace provides the alternate heating source.
Electric Baseboards
Ductless and other heat pump retrofits may retain baseboards in:
- Bedrooms
- Bathrooms
- Unserved rooms
- Backup areas
Other Heating Systems
Depending on the building and system design, supplementary heating can also involve other approved equipment.
The Thermostat Display Does Not Always Tell You the Physical Heat Source
Before interpreting AUX or Emergency Heat, determine whether the home’s backup is:
- Electric resistance
- Gas furnace
- Independent electric heaters
- Another system
1. AUX Heat Normally Turns On Automatically
In a properly configured system, homeowners generally do not manually turn AUX Heat on.
The thermostat or equipment controls determine when supplementary capacity is required.
AUX Heat May Be Requested Because:
- The outdoor temperature is low.
- The building load exceeds current heat-pump capacity.
- The thermostat is recovering from a large setback.
- The heat pump is in defrost.
- The equipment control strategy calls for another heating stage.
Seeing AUX on the Thermostat Is Therefore Not Automatically a Fault
The important questions are:
- How cold is it outside?
- How long is AUX running?
- Can the home maintain temperature?
- Does AUX turn off once demand decreases?
2. Emergency Heat Is Usually a Backup-Only Operating Mode
Many thermostats for central heat pump systems include an Emergency Heat or EM Heat mode.
What Common Thermostats Do
On many thermostat-controlled systems, selecting Emergency Heat:
- Locks out normal heat-pump compressor heating
- Uses the configured emergency or backup heating source
Why Would You Want to Lock Out the Heat Pump?
For example, when the refrigeration system cannot provide normal heating because of a confirmed equipment fault.
Emergency Heat Does Not Make the House Heat Faster by Magic
It changes which heating source is being used.
It should not be treated as a winter “turbo” button.
Not Every Heat Pump Has an Emergency Heat Mode
Availability depends on:
- Thermostat
- Equipment type
- Backup heat
- Installer configuration
3. AUX Heat Can Be Completely Normal
Occasional supplementary heating can be part of the intended design.
Example: Very Cold Weather
As outdoor temperature falls:
- The home’s heat loss increases.
- The heat pump’s available capacity can change.
At some point, the system may need additional heating capacity.
Example: Defrost
During defrost, the heat pump temporarily directs heat toward the outdoor coil.
Supplementary heating can help prevent uncomfortable cold air from being distributed indoors during that period.
Example: Temperature Recovery
If the thermostat was set several degrees lower and is suddenly raised, the control system may request auxiliary heating to recover the temperature faster.
Normal Does Not Mean Unlimited
AUX Heat operating for hours every mild day deserves a different conversation from AUX appearing briefly during a cold morning.
4. Electric AUX Heat Uses More Electricity for the Same Useful Heat
This is why unnecessary electric auxiliary heating matters.
Heat Pump Heating
A heat pump transfers thermal energy.
When operating at a COP above 1, it supplies more useful heat than the electrical energy directly consumed by the equipment.
Electric Resistance Heating
Natural Resources Canada describes electric resistance heaters as producing approximately one unit of heat for each unit of electricity consumed at the point of use.
Simple Example
If a heat pump is operating at a COP of 3 under a particular condition, delivering three units of heat requires approximately one unit of compressor-system electrical input.
Resistance heat would require approximately three units of electrical input to deliver the same three units of direct resistance heat.
This Is an Illustration, Not a Seasonal Savings Guarantee
Actual system consumption also depends on:
- Fans
- Defrost
- Outdoor temperature
- Equipment performance
- Building load
Why Emergency Heat Can Affect the Bill
If Emergency Heat locks out an operating heat pump and relies only on electric resistance backup, the home may use substantially more electricity for space heating.
5. Cold Weather Can Increase Auxiliary Heat Use
Cold weather creates two simultaneous effects.
The Home Needs More Heat
Heat loss through:
- Walls
- Windows
- Roof
- Doors
- Air leakage
increases as the indoor-to-outdoor temperature difference becomes larger.
Heat Pump Capacity Can Change
Air-source heat pump heating capacity and efficiency vary with outdoor temperature.
Eventually, Supplementary Heat May Be Needed
Natural Resources Canada identifies the thermal balance point as the condition where heat pump capacity equals the building heating load.
Below that point, supplementary heating may be required if heat pump capacity alone cannot satisfy the building load.
Cold-Climate Heat Pumps Can Shift This Relationship
A model with stronger low-temperature capacity may carry a larger portion of the winter heating load before supplementary heating is required.
6. Large Thermostat Setbacks Can Trigger AUX Heat
Heat pumps generally work well maintaining a relatively steady indoor temperature.
Consider This Scenario
The thermostat is reduced from 21°C to 17°C overnight.
At 6 a.m., it is suddenly raised back to 21°C.
The thermostat sees a four-degree recovery demand and may request additional heating stages.
The Result Can Be:
- Heat pump running at high capacity
- AUX Heat operating
- Higher short-term electricity demand
ENERGY STAR Guidance
ENERGY STAR currently recommends choosing a comfortable temperature and keeping heat-pump settings relatively steady rather than relying on large routine setbacks.
See the official ENERGY STAR air-source heat pump guidance.
Small Adjustments Are Different From Aggressive Recovery
The objective is not that the thermostat can never be changed.
The problem is repeatedly creating a large heating recovery that unnecessarily calls for resistance backup.
7. Defrost Can Temporarily Require Supplementary Heat
During winter heating, moisture can freeze on the outdoor coil.
The heat pump periodically needs to remove that frost.
During a Common Defrost Sequence
- The refrigeration cycle changes temporarily.
- The outdoor coil receives heat.
- The outdoor fan may stop.
- Steam or water may appear outside.
- Indoor heat-pump output temporarily changes.
Supplementary Heating Can Maintain Indoor Comfort
Natural Resources Canada notes that supplementary heating may be used while an air-source heat pump is defrosting.
Brief AUX During Defrost Is Not Automatically a Problem
Investigate when:
- Defrost happens excessively
- The outdoor coil remains heavily iced
- AUX continues long after defrost ends
- The home repeatedly loses temperature
8. The Thermal Balance Point Matters
The thermal balance point helps explain why backup heat exists.
Above the Balance Point
The heat pump has enough capacity to satisfy the building load on its own under the design assumptions.
At the Balance Point
Heat pump capacity approximately equals the home’s heating requirement.
Below the Balance Point
The building may need additional heat beyond what the heat pump can provide alone.
Balance Point Is Not One Universal BC Temperature
It depends on:
- Home heat loss
- Heat pump capacity
- Equipment performance
- Thermostat and control strategy
Two Identical Heat Pumps Can Have Different Balance Points
A well-insulated smaller home and a drafty larger home can require very different heating capacity from the same equipment.
9. Dual-Fuel Backup Works Differently From Electric AUX Heat
A heat pump paired with a gas furnace should not automatically be treated like an all-electric heat pump with resistance strips.
All-Electric Central System
Heat pump and electric resistance supplementary heat can operate together in an appropriate design.
Common Dual-Fuel System
The system switches between:
- Heat pump heating
- Furnace heating
according to the configured hybrid strategy.
Natural Resources Canada
NRCan describes common hybrid systems as operating one heating source or the other rather than simultaneously using the heat pump and fuel-fired furnace.
Thermostat Terminology Can Still Say AUX or Backup Heat
The physical heat source may be a furnace rather than electric resistance heaters.
That Is Why Homeowners Need to Know What Equipment They Actually Have
A thermostat label is not a complete mechanical-system diagram.
10. Emergency Heat Should Not Be a Routine Efficiency Setting
Emergency Heat is not the mode homeowners should select every winter because outdoor temperatures feel cold.
On Many Systems, Emergency Heat Disables Compressor Heating
The system then relies on its configured backup source.
If the Backup Is Electric Resistance
This can increase electricity use significantly compared with normal heat-pump operation.
If the Backup Is a Furnace
The home may use fuel heating instead of the heat pump.
Normal Heat Mode Is Designed to Handle Heating Decisions
When the equipment is functioning correctly, thermostats and heat pump controls should normally manage:
- Compressor heating
- Supplementary heat
- Balance-point strategy
- Defrost
Use Emergency Heat for the Purpose Intended by Your System
That generally means temporary backup operation when normal heat-pump heating is unavailable or when instructed by a qualified technician or manufacturer guidance.
11. Continuous AUX Heat in Mild Weather Can Indicate a Problem
If outdoor conditions are relatively mild and AUX Heat remains active for long periods, determine why.
Possible Causes Include:
- Thermostat configuration
- Large temperature recovery
- Outdoor sensor error
- Heat pump not producing enough heat
- Restricted indoor airflow
- Dirty filter
- Outdoor airflow problem
- Refrigerant-system problem
- Equipment fault
- Heat pump undersizing
- Building heat loss greater than expected
Look at Comfort Too
Continuous AUX accompanied by:
- Weak heat
- Falling room temperature
- Outdoor unit not running
- Heavy icing
- Fault codes
provides a stronger reason for service.
Do Not Diagnose From the AUX Indicator Alone
The technician needs to determine why the control requested backup heat.
12. Thermostat Configuration Can Cause Unnecessary Backup Heat
The thermostat does much more than display room temperature.
Installer Settings Can Affect:
- Heat-pump staging
- Auxiliary heat staging
- Outdoor-temperature lockouts
- Recovery behaviour
- Dual-fuel changeover
- Reversing-valve operation
BC Hydro Best-Practice Guidance
BC Hydro’s current heat pump retrofit guidance recommends configuring electric supplementary heat so it does not operate above the heat pump’s balance point except where needed for functions such as defrost or emergency heating.
Thermostat Replacement Can Create Problems
If a new thermostat is installed with incorrect equipment settings, possible results include:
- AUX operating too early
- Heat pump not operating
- Wrong reversing-valve operation
- Backup heat not operating
- Furnace changeover problems
Do Not Copy Installer Settings From Another House
Equipment type and control strategy can be different even when the thermostat looks identical.
13. Backup Heat Does Not Automatically Mean the Heat Pump Is Undersized
Supplementary heating can be an intentional design choice.
Why Not Size Every Heat Pump for the Absolute Peak Load?
A much larger heat pump may operate poorly during the many hours when the home needs only a small amount of heat.
Oversizing can contribute to:
- Frequent cycling
- Reduced mild-weather efficiency
- Comfort problems
Supplementary Heat Can Cover Rare Peak Conditions
A system can be designed so the heat pump supplies most annual heating energy while another source covers selected peak loads.
But Excessive Backup Use Can Indicate Undersizing
The question is whether supplementary heating operates:
- As expected by the design
- Far more frequently than expected
Load Calculation Helps Answer That
Compare:
- Building heating load
- Heat pump capacity curve
- Balance point
- Actual outdoor conditions
14. Commissioning Should Verify Backup-Heat Operation
A heat pump installation is not complete just because heating and cooling both turn on.
For All-Electric Systems, Commissioning May Include:
- Heat pump heating
- Electric auxiliary stages
- Emergency Heat
- Defrost-support operation
- Outdoor-temperature controls
For Dual-Fuel Systems
Verify:
- Heat pump heating
- Furnace heating
- Changeover strategy
- Thermostat configuration
- Outdoor sensor or control data
Airflow Matters
Electric heat kits and furnaces both depend on appropriate indoor airflow.
Commissioning should therefore also consider:
- Blower setup
- Filter pressure drop
- Duct static pressure
- Supply airflow
The Homeowner Should Receive an Explanation
Before handover, the homeowner should know:
- What AUX means
- What Emergency Heat means
- Which physical equipment provides backup heat
- When backup operation is expected
When Is AUX Heat Normal?
AUX Heat can be normal in several situations.
Very Cold Weather
The building load may exceed current heat-pump capacity.
Defrost
Supplementary heating may operate briefly while the outdoor coil is being defrosted.
Large Temperature Recovery
A large thermostat increase can cause the control system to request additional heating stages.
System Startup After a Long Temperature Drop
The same recovery behaviour can occur after:
- Power outage
- Thermostat being left low
- Extended absence
Temporary Peak Load
Wind, unusual cold or other building-load conditions can increase heating demand.
What Normal AUX Usually Does
It should stop when:
- Heating demand decreases
- Indoor temperature recovers
- Defrost ends
- The heat pump can carry the load again
When Should AUX Heat Be Investigated?
Arrange professional evaluation when AUX operation changes unexpectedly or appears inconsistent with conditions.
Examples Include:
- AUX runs almost continuously during mild weather.
- The outdoor heat pump does not run.
- The home cannot maintain temperature.
- AUX usage suddenly increased compared with previous winters.
- Electricity consumption rose sharply without a matching weather change.
- The outdoor coil is covered in heavy persistent ice.
- The thermostat displays recurring faults.
- AUX remains active long after a small temperature recovery.
AUX Itself Is the Symptom, Not Necessarily the Cause
Diagnosis needs to determine whether the problem comes from:
- Controls
- Heat pump capacity
- Heat pump performance
- Airflow
- Building load
When Should Emergency Heat Be Used?
Emergency Heat is generally appropriate when normal heat-pump heating cannot be used and the backup system needs to maintain indoor temperature.
Possible Example
A confirmed heat-pump refrigeration or outdoor-unit fault prevents normal heating, while the backup heat source remains functional.
Emergency Heat Is Temporary Backup
It can maintain comfort while service is arranged.
It Is Not a Repair
Emergency Heat does not fix:
- Compressor problem
- Refrigerant leak
- Outdoor fan failure
- Defrost fault
- Electrical fault
Use the Equipment Instructions
Control behaviour varies by manufacturer and system.
Some systems may automatically manage backup during specific failures without requiring the homeowner to select Emergency Heat manually.
What if Emergency Heat Was Left On Accidentally?
First, do not panic.
Check the Thermostat Mode
If Emergency Heat was accidentally selected and there is no known heat-pump failure, review the thermostat operating instructions and return the system to normal Heat mode if appropriate.
Then Observe the Heat Pump
Confirm that normal heating resumes and the home maintains temperature.
Why the Bill May Be Higher
If the system used electric resistance heat instead of compressor heating for an extended period, electricity consumption may have increased.
Arrange Service When:
- The heat pump does not resume operation.
- The thermostat immediately returns to backup-only operation.
- Fault codes appear.
- The home loses heat without Emergency Heat.
How Much Can AUX Heat Affect the Electricity Bill?
There is no universal dollar amount.
The effect depends on:
- Backup heater capacity
- Runtime
- Heat pump COP
- Outdoor temperature
- Building heating load
- Electricity rate
Electric Resistance Backup Is the Key Concern
Natural Resources Canada explains that resistance heat provides one unit of heat for one unit of electricity at the point of use.
A heat pump can deliver multiple units of useful heat per unit of electricity under suitable conditions.
Therefore, More Resistance Heat Usually Means More Heating kWh
This is particularly noticeable when:
- Emergency Heat is left on
- AUX runs continuously
- A large resistance heater operates for many hours
Do Not Diagnose From the Dollar Bill Alone
Compare:
- kWh
- Outdoor weather
- AUX runtime
- Thermostat settings
- Other household loads
AUX and Emergency Heat in Full-Electric Heat Pump Systems
A common central full-electric configuration includes:
- Outdoor heat pump
- Indoor air handler
- Electric resistance heat kit
Normal Heating
The heat pump should supply the majority of heating according to the system design.
AUX Heat
Electric resistance stages can supplement heat pump capacity when controls determine additional heat is needed.
Emergency Heat
On compatible thermostats, backup resistance heat can provide heating while normal heat-pump compressor heating is locked out.
Electrical Capacity Matters
Resistance backup heaters can represent a significant electrical load.
The heat kit capacity should therefore be considered during:
- HVAC sizing
- Panel planning
- Electrical load calculation
- Commissioning
AUX and Emergency Heat in Dual-Fuel Systems
Dual fuel combines an electric heat pump with a fuel-fired furnace.
Normal Heat Pump Operation
The compressor provides heating through the selected operating range.
Furnace Operation
The furnace becomes the heating source according to the hybrid switch-over strategy.
The Furnace Is Not an Electric Heat Strip
Control logic must prevent inappropriate simultaneous operation in common furnace-plus-heat-pump designs.
Thermostat Displays Can Be Confusing
A thermostat may use words such as:
- Aux
- Backup
- Stage 2
even though the actual backup source is the gas furnace.
Know Your Changeover Strategy
The homeowner should understand:
- When heat-pump heating is expected
- When furnace heating is expected
- What the thermostat displays during each mode
Heat Pumps With Electric Baseboard Backup
Ductless heat pump retrofits frequently retain selected hard-wired electric heaters.
Baseboards Can Serve:
- Bedrooms without direct heat pump coverage
- Bathrooms
- Peak heating needs
- Emergency backup
Independent Thermostats Can Create Overlap
If a baseboard thermostat is set higher than the heat pump setpoint, resistance heating may operate before the heat pump can satisfy the room or adjacent area.
BC Hydro Retrofit Guidance
BC Hydro’s current contractor guide recommends setting independent supplementary heating thermostats such as baseboards below the normal heat pump setting and considering interlocks that prevent unnecessary simultaneous operation.
The Exact Temperature Difference Is Project-Specific
It should reflect:
- Room load
- Heat pump coverage
- Comfort requirements
- Backup strategy
Do Ductless Heat Pumps Have AUX or Emergency Heat?
Not necessarily.
Many Mini-Splits Do Not Contain Central Electric Heat Strips
A wall-mounted ductless system may rely entirely on compressor heat within its normal operating range.
Supplementary Heating May Exist Separately
For example:
- Electric baseboards
- Another ductless system
- Central heating equipment
The Ductless Remote May Not Display “AUX”
This does not mean the home has no backup heat.
The backup may simply be controlled independently.
Emergency Heat Mode Is More Common on Central Thermostat-Controlled Systems
Do not expect every ductless remote or manufacturer app to offer the same modes as a conventional central thermostat.
Safe Homeowner Checks When AUX Heat Seems Excessive
1. Check the Thermostat Mode
Confirm the system is in normal Heat mode rather than Emergency Heat.
2. Check the Setpoint
Avoid raising the temperature several degrees at once while troubleshooting.
3. Check the Schedule
Look for large automatic setbacks and morning recovery.
4. Inspect the Filter
A dirty filter can reduce airflow and heating performance.
5. Check Supply and Return Openings
Do not block registers or return grilles with:
- Furniture
- Rugs
- Boxes
6. Look at the Outdoor Unit From a Safe Distance
Check for:
- Heavy ice buildup
- Snow blocking airflow
- Debris
- Outdoor fan not operating during normal heating outside defrost
7. Note the Outdoor Temperature
AUX behaviour during an unusually cold period may be different from mild-weather behaviour.
8. Record What the Thermostat Displays
Useful information includes:
- AUX Heat
- Emergency Heat
- Fault code
- Indoor temperature
- Setpoint
What Homeowners Should Not Do
Do Not Select Emergency Heat Just Because It Is Cold Outside
Normal Heat mode is designed to manage ordinary heat-pump operation.
Do Not Disable Backup Heat Permanently to Save Electricity
Supplementary heat may be required for:
- Peak load
- Defrost
- Equipment failure
Do Not Change Hidden Installer Settings Randomly
These settings can affect:
- Compressor operation
- Auxiliary heat
- Dual-fuel changeover
- Defrost support
Do Not Increase Breaker Size
If auxiliary heat or the heat pump trips electrical protection, the equipment needs diagnosis.
Do Not Assume AUX Means the Heat Pump Is Broken
First consider outdoor conditions and operating pattern.
Do Not Assume AUX Is Normal Forever Either
Continuous unexplained backup heat can hide a real heat pump or control problem.
How Does a Technician Diagnose Excessive AUX Heat?
The objective is to determine why the thermostat or equipment requested supplementary heating.
1. Review the Complaint and History
Important information includes:
- When AUX appears
- Outdoor temperature
- Thermostat settings
- Recent electrical bills
- Recent thermostat or equipment changes
2. Check Thermostat Configuration
The technician may verify:
- Heat pump equipment type
- Auxiliary stages
- Emergency Heat configuration
- Outdoor-temperature lockout
- Balance-point settings
- Recovery settings
3. Confirm Heat Pump Heating Performance
Testing can include:
- Compressor operation
- Outdoor fan
- Indoor temperature performance
- Refrigeration-system measurements
- Fault history
4. Check Airflow
For ducted equipment:
- Filter
- Blower
- Static pressure
- Coil condition
- Registers and returns
5. Check Electric Backup Heat
The technician can determine:
- Which stages energize
- When they energize
- Whether expected electrical current is present
- Whether controls turn them off correctly
6. Check Dual-Fuel Operation Where Applicable
Verify heat pump and furnace changeover rather than testing the two appliances independently and assuming their marriage is healthy.
7. Compare Capacity With the Building Load
If equipment functions correctly but AUX is genuinely needed much of the season, system sizing or building heat loss may need review.
Does Excessive AUX Heat Mean Repair, Redesign or Replacement?
It depends on the cause.
Repair May Be Appropriate For:
- Failed sensor
- Thermostat configuration
- Blower problem
- Outdoor fan problem
- Refrigeration fault
- Control board problem
Commissioning or Redesign May Be Needed For:
- Incorrect backup-heat staging
- Poor balance-point configuration
- High duct static pressure
- Dual-fuel control problems
- Large thermostat setback strategy
Building Improvements May Help When:
The home has excessive heat loss from:
- Air leakage
- Low insulation
- Poor windows
Replacement May Make Sense When:
- The heat pump is near the end of its useful service life.
- Major components have failed.
- Low-temperature capacity is poorly matched to the home.
- The system was fundamentally misapplied and redesign cannot reasonably correct it.
Do Not Replace a Heat Pump Solely Because AUX Appears
Backup heat is a designed component of many systems.
Heat Pump AUX and Emergency Heat Service in Metro Vancouver and Fraser Valley
Bernoulli Heating and Cooling services existing heat pump systems across Metro Vancouver and Fraser Valley.
If AUX Heat is running unexpectedly, Emergency Heat appears necessary for normal comfort or the heat pump is no longer providing normal heating, diagnosis can include thermostat controls, backup heating, airflow, defrost operation, outdoor equipment and refrigeration-system performance.
The current diagnostic appointment charge for an existing heat pump is $135. Repair labour, replacement parts, materials and refrigerant are separate.
New heat pump installation estimates are free.
Call 604-518-4438 or email heatingbernoulli@gmail.com.
Explore local installation information:
Heat Pump AUX Heat vs Emergency Heat: Frequently Asked Questions
What does AUX Heat mean on a thermostat?
It generally means the heat pump system has called for its supplementary or backup heating source in addition to or instead of normal compressor heating, depending on the system design.
Is AUX Heat the same as Emergency Heat?
No. AUX Heat is normally requested automatically, while Emergency Heat is commonly a backup-only mode used when normal heat-pump heating should not operate.
Does AUX Heat mean something is wrong?
Not necessarily. AUX can be normal during cold weather, defrost or large temperature recovery.
Does Emergency Heat mean something is wrong?
Emergency Heat is commonly intended for situations where normal heat-pump heating is unavailable. If you need Emergency Heat to stay comfortable under ordinary conditions, the system should be evaluated.
Does AUX Heat turn on automatically?
Yes in common heat pump systems. Thermostat or equipment controls determine when supplementary heating is required.
Do I manually turn AUX Heat on?
Normally no. The system controls its auxiliary stages automatically.
Do I manually turn Emergency Heat on?
Many central thermostats provide a manual Emergency Heat mode, although available modes and behaviour vary by system.
What happens when I select Emergency Heat?
On many thermostat-controlled central systems, compressor heating is locked out and the configured emergency or backup heat source maintains the setpoint.
Does the outdoor unit run in Emergency Heat?
On common systems where Emergency Heat locks out the compressor, normal outdoor heat-pump heating does not operate. Exact behaviour depends on equipment and controls.
Does the outdoor unit run with AUX Heat?
It can in an all-electric system where electric resistance heat supplements compressor heating.
Can the heat pump and electric heat strips run together?
Yes in appropriately designed all-electric systems.
Can the heat pump and gas furnace run together?
In the common hybrid configuration described by Natural Resources Canada, controls switch between the heat pump and fuel-fired furnace rather than operating them simultaneously.
What provides AUX Heat in my house?
It may be electric heat strips, a furnace, baseboards or another supplementary source depending on the system.
How do I know if I have electric heat strips?
Review the air-handler equipment documentation or installation records. A technician can also identify the installed backup equipment.
Where are electric heat strips located?
In common central all-electric systems, resistance heating elements are installed in or with the indoor air handler or ducted heating equipment.
What is backup heat?
Backup heat is another heating source available when heat-pump heating alone does not meet the intended demand or cannot operate normally.
Is supplementary heat the same as backup heat?
The terms are often used similarly, although manufacturers and control systems can use different terminology.
What is Stage 2 Heat?
It can refer to a second heating stage. On some heat pump systems that stage is auxiliary heat, while other equipment may use different staging arrangements.
Why is AUX Heat on when it is cold outside?
The home’s heating load may exceed the heat pump’s available capacity under those conditions.
What temperature should AUX Heat turn on?
There is no universal temperature. It depends on building load, equipment capacity and control configuration.
What is the thermal balance point?
It is the outdoor condition where the heat pump’s available heating capacity approximately equals the building heating load.
Does AUX always come on below the balance point?
The operating strategy depends on controls and system design. In an all-electric system, additional resistance heat may be staged as required.
Does a cold-climate heat pump need AUX Heat?
It may. Cold-climate equipment can provide stronger low-temperature performance, but backup needs still depend on building load and system design.
Can a heat pump be designed without electric backup heat?
Yes in some systems, particularly when another backup source exists or equipment capacity and design make resistance backup unnecessary.
Does every heat pump need backup heat?
No universal backup configuration applies to every heat pump. The need depends on equipment, climate, load and installation objectives.
Does every ductless mini-split have AUX Heat?
No. Many ductless systems do not contain central resistance heat strips.
Does every mini-split have Emergency Heat?
No. Emergency Heat is more commonly associated with central heat pump thermostats controlling a separate backup source.
Can electric baseboards be heat pump backup?
Yes in appropriately designed homes. They may provide supplementary heat in rooms or conditions not fully served by the heat pump.
Should I leave the baseboards on?
That depends on the heating design. They should not unnecessarily compete with the heat pump, but rooms requiring supplementary heating still need a reliable heat source.
Should baseboards be set lower than the heat pump?
BC Hydro’s current retrofit guidance recommends lower settings for independent supplementary thermostats so the heat pump remains the primary heat source. The exact setting should match the project design.
Why did AUX turn on after I raised the thermostat?
A large temperature increase can create a recovery demand that causes the thermostat to request supplementary heat.
Should I avoid thermostat setbacks?
Large routine setbacks can increase backup-heat use. ENERGY STAR currently recommends relatively steady heat pump temperature settings.
Can I lower the thermostat at night?
You can adjust comfort settings, but aggressive setbacks followed by large recovery demands may activate AUX Heat.
Why does AUX come on in the morning?
A programmed overnight setback followed by a morning temperature increase is a common reason.
Can a smart thermostat prevent unnecessary AUX Heat?
A compatible, correctly configured thermostat can manage staging and recovery more effectively, but installer configuration still needs to match the heat pump and backup system.
Can the wrong thermostat make AUX run too much?
Yes. Incorrect compatibility or installer settings can cause poor staging, wrong heat-pump control or unnecessary backup operation.
Can thermostat wiring cause AUX problems?
Yes. Control wiring and configuration problems can affect compressor and backup heating operation.
Should I change installer settings myself?
Not unless the equipment instructions clearly call for a homeowner adjustment. Incorrect installer settings can affect heating-system operation and safety.
Why does AUX come on during defrost?
The heat pump temporarily redirects heat toward the outdoor coil during defrost. Supplementary heat can maintain indoor comfort during that process.
How long should AUX stay on after defrost?
There is no universal duration. It should return to ordinary control once defrost and the related heating demand are satisfied.
Why is steam coming from the outdoor unit while AUX is on?
Visible vapour can occur when frost melts from the outdoor coil during normal defrost.
Does defrost increase electricity use?
It uses energy, and electric supplementary heat may also operate during defrost depending on the system.
Is AUX Heat expensive?
Electric resistance AUX can use significantly more electricity for the same delivered heat than compressor heating operating at a COP above 1.
Is Emergency Heat expensive?
It can be when the backup source is electric resistance heat because normal heat-pump compressor heating may be locked out.
How much does Emergency Heat cost per hour?
There is no universal amount. It depends on backup-heater capacity, staging, runtime and the applicable electricity rate.
Can a 10 kW heat kit use 10 kWh in one hour?
If the entire 10 kW resistance heater operated continuously at full output for one hour, its energy consumption would be approximately 10 kWh. Actual staged systems may not operate every element continuously.
Why is my electric bill high after using Emergency Heat?
If compressor heating was replaced by prolonged electric resistance heating, space-heating electricity use can increase significantly.
Can AUX cause a high electric bill?
Yes when resistance backup operates frequently or for long periods.
How can I tell whether AUX caused my high bill?
Compare thermostat history where available, outdoor weather, electricity consumption and heating behaviour. A technician can verify staging and controls.
Is AUX Heat less efficient than the heat pump?
Electric resistance AUX generally requires more electrical input for the same useful heat than a heat pump operating at a COP above 1.
Is gas-furnace AUX less efficient?
That comparison depends on heat-pump COP, furnace efficiency, utility prices and operating conditions. Gas backup also works differently from electric resistance staging.
Should I use Emergency Heat when it is below freezing?
No, not simply because it is below 0°C. Modern air-source heat pumps are designed to operate below freezing within their rated operating range.
Should I use Emergency Heat during a snowstorm?
Not solely because it is snowing. Use normal Heat mode unless the equipment instructions or a confirmed system problem indicate backup-only operation is needed.
Should I use Emergency Heat if the outdoor unit is covered in ice?
Heavy persistent ice can indicate a defrost or airflow problem. Avoid damaging the unit and arrange diagnosis. The appropriate temporary heating mode depends on the specific system and condition.
Should I use Emergency Heat if the outdoor fan stops?
The outdoor fan can stop normally during defrost. If it remains stopped during normal heating and the system is not producing heat, service may be required.
Can I run Emergency Heat overnight?
It can provide temporary backup where the system is designed for it, but prolonged operation should not substitute for repairing a failed heat pump.
Can Emergency Heat damage the heat pump?
Properly configured Emergency Heat is an intended control mode. It normally prevents compressor heating rather than forcing a damaged compressor to operate.
Can leaving Emergency Heat on damage anything?
The backup system is designed to heat the home, but extended unnecessary operation can increase energy use and places more runtime on the backup equipment.
What if Emergency Heat keeps turning itself on?
Some systems may automatically use backup during faults, while others require manual selection. Repeated unexpected backup-only operation should be diagnosed.
Why is the outdoor unit off but the house is warm?
The system may be using electric resistance backup, a furnace or another heating source.
Why is the thermostat showing AUX but the outdoor unit is off?
Possible reasons include control strategy, compressor lockout, equipment fault or a backup-only stage. The exact cause depends on the system.
Why is the outdoor unit running while AUX is displayed?
This can be normal in an all-electric system where resistance heating supplements heat-pump compressor operation.
Why won’t AUX Heat turn off?
Possible causes include continued high heating demand, thermostat configuration, sensor error or weak heat-pump performance.
Can a dirty filter cause more AUX Heat?
Yes. Restricted airflow can reduce delivered heat and cause the thermostat to request additional heating.
Can blocked return air cause AUX Heat?
It can contribute to poor system airflow and reduced heating performance.
Can low refrigerant cause excessive AUX Heat?
Yes. A refrigeration problem can reduce heat-pump capacity and increase reliance on backup heating.
Can a dirty outdoor coil cause excessive AUX Heat?
Restricted heat transfer or airflow can reduce heating performance.
Can a defrost problem increase AUX usage?
Yes. Persistent icing can reduce outdoor heat transfer and cause the system to depend more heavily on backup heat.
Can an undersized heat pump use lots of AUX?
Yes, particularly during colder conditions if available heat-pump capacity is below the building load.
Can an oversized heat pump cause AUX problems?
Oversizing can create cycling and control issues, although excessive AUX use is not automatically caused by oversizing.
Does frequent AUX mean I need a bigger heat pump?
Not necessarily. Check controls, airflow, equipment performance and building load before considering replacement.
Can improving insulation reduce AUX Heat use?
Yes. Lower building heat loss can reduce the amount of supplemental heating required during cold conditions.
Can new windows reduce backup heat use?
They may when they meaningfully reduce building heat loss or air leakage.
Should AUX Heat be included in heat pump sizing?
Yes. The heating design should identify heat-pump capacity, building load, expected balance point and supplementary-heating strategy.
Should AUX Heat be tested during installation?
Yes. Backup stages and controls should be commissioned as part of the complete system.
Should Emergency Heat be tested during commissioning?
Where the system has an Emergency Heat mode, its correct operation should be verified.
Should I know the balance point of my heat pump?
It can be useful, particularly for understanding expected backup operation and verifying thermostat configuration.
Can the balance point change?
The underlying relationship can change if the building load changes through renovations or if equipment capacity changes because of system condition.
What if AUX started appearing only after a thermostat replacement?
Thermostat compatibility, wiring and installer settings should be reviewed.
What if AUX began after a power outage?
Check thermostat mode and settings. Some controls may also need to recover from an indoor temperature drop after the outage.
What if AUX runs after heat pump maintenance?
If the behaviour is new and persistent, verify that controls, sensors and equipment settings were restored correctly.
Should I call for service if AUX appears once?
No. Occasional AUX can be normal. Look for repeated, prolonged or unexplained operation.
When should I call for service?
Arrange diagnosis when AUX runs continuously in mild weather, Emergency Heat is required for ordinary heating, the heat pump does not operate normally, the home loses temperature or faults and heavy icing occur.
What does Bernoulli charge for diagnosis?
Bernoulli Heating and Cooling currently charges $135 for a diagnostic appointment on an existing heat pump. Repair labour, parts, materials and refrigerant are separate.
Does Bernoulli charge for new heat pump installation estimates?
New heat pump installation estimates are currently free.