What is the main difference between Heat and Em Heat?

The main difference is that Heat uses your heat pump to extract warmth from outdoor air, while Em Heat activates the electric resistance backup heating strips inside your indoor unit.

Which is better, Heat or Em Heat, for warming a home?

Heat is better for normal winter conditions because it is far more energy-efficient, whereas Em Heat is better only as an emergency backup when the outdoor unit fails or is frozen.

Does using Em Heat cost more than using Heat?

Yes, using Em Heat costs significantly more because electric resistance strips produce roughly three times less heat per dollar compared to the heat pump's efficient refrigerant cycle.

Is it safe to run Em Heat for an extended period?

Yes, it is safe to run Em Heat for an extended period because it is designed for continuous operation, but doing so will cause a substantial spike in your electricity bill.

Can Em Heat be used with any type of thermostat?

No, Em Heat can only be used with a thermostat that has a dedicated emergency heat terminal and a system configured with electric backup heat strips.

What is a common beginner mistake with Heat and Em Heat settings?

A common beginner mistake is manually switching to Em Heat during a cold snap, which forces expensive backup strips to run instead of letting the heat pump work efficiently.

Are Heat and Em Heat interchangeable settings on a thermostat?

No, Heat and Em Heat are not interchangeable because Heat relies on the outdoor compressor, while Em Heat bypasses that compressor entirely and uses only the indoor electric strips.

When should a homeowner actually switch the thermostat to Em Heat?

You should switch to Em Heat only when the outdoor heat pump unit is broken, iced over, or not producing warm air, and you need heat while waiting for a repair.

Can I switch from Heat to Em Heat while the system is running?

Yes, you can switch from Heat to Em Heat while the system is running because the thermostat will safely deactivate the compressor and activate the backup strips within a minute.

Does Em Heat damage the heat pump system over time?

No, Em Heat does not damage the heat pump system itself, but overusing it wastes energy and can shorten the lifespan of the electric heating elements.

Difference Between

Difference Between Heat and Em Heat

Written byNex Virox Team

Editorial Team

Reviewed byVarshal Nirbhavane

Senior SEO & Organic Growth Professional · 5+ years

Published: September 7, 202622 min read

Quick answer

The main difference between Heat and Em Heat is that Heat uses the furnace or heat pump, while Em Heat is an emergency backup mode. Heat is the standard heating setting for everyday use, while Em Heat is a manual override that activates electric resistance strips. Use Em Heat only when your primary heating system fails.

Key takeaways

Core distinction: Heat mode runs the compressor for efficient air warming, while Em Heat uses only the electric heat strips.
How each works: Heat pumps extract warmth from outdoor air; Em Heat bypasses the pump and directly converts electricity into heat.
Cost and performance: Em Heat costs 2–3 times more per BTU than standard heat pump operation, making it a costly backup.
Best-fit use case: Use Em Heat only during defrost cycles, extreme cold below 30°F, or when the heat pump fails.
Most common mistake: Manually switching to Em Heat during mild weather wastes energy and raises utility bills unnecessarily.

Table of Contents18 sections

Difference Between Heat and Em Heat: Comparison Table

Aspect	Heat	Em Heat
Definition	Primary heating mode using a heat pump to transfer warmth from outdoor air.	Emergency heating mode that activates electric resistance strips inside the air handler.
Purpose	Provides efficient日常 heating for most winter conditions down to freezing temperatures.	Delivers backup heat when outdoor temperatures drop below the heat pump's operating range.
Core Mechanism	Uses refrigerant cycles to extract heat from outside air and compress it indoors.	Relies on electric coils that generate heat directly through resistance when energized.
Energy Source	Consumes electricity to run compressor and fans, not for direct heat generation.	Draws high electrical current directly into resistive heating elements for immediate warmth.
Efficiency Rating	Typical COP ranges from 2.5 to 4.0, meaning 250-400% efficiency in moderate climates.	COP is always 1.0, converting every watt of electricity into exactly one watt of heat.
Operating Cost	Costs roughly one-third to one-half of electric resistance heating per BTU delivered.	Costs 2-3 times more per BTU than heat pump operation due to lower efficiency.
Temperature Range	Operates effectively down to 25-35°F, with newer models working at -10°F.	Functions at any outdoor temperature but is typically only used below 25-30°F.
Heat Output	Produces moderate, consistent airflow at 90-110°F from supply vents during normal operation.	Generates intense heat at 110-130°F from vents, warming rooms noticeably faster.
Response Time	Takes 10-20 minutes to reach target temperature due to gradual refrigerant cycle warming.	Delivers noticeable warmth within 2-5 minutes because electric coils heat instantly.
System Wear	Runs compressor and outdoor fan regularly, causing normal mechanical wear over years.	Activates rarely but stresses electrical components and blower motor when engaged.
Maintenance Needs	Requires annual filter changes, coil cleaning, and refrigerant level checks every 1-2 years.	Needs periodic inspection of heating elements and safety limit switches for corrosion.
Safety Features	Includes high-pressure switches and defrost cycles to prevent compressor damage in cold weather.	Has thermal cutoff switches and fusible links to prevent overheating and fire hazards.
Airflow Pattern	Produces lower velocity airflow at around 350-400 CFM per ton of capacity.	Pushes higher airflow at 400-450 CFM per ton to distribute intense heat quickly.
Humidity Impact	Removes 1-3 pints of moisture per hour during heating, maintaining comfortable indoor humidity.	Adds no moisture removal, potentially leaving air feeling drier during extended use.
Noise Level	Emits 50-70 dB from outdoor compressor and indoor blower during normal cycling.	Produces only indoor blower noise at 40-60 dB since no outdoor unit operates.
Defrost Cycle	Periodically reverses refrigerant flow for 5-10 minutes to melt ice from outdoor coils.	Does not require defrosting because electric resistance elements generate heat directly.
Thermostat Setting	Selected manually as "Heat" mode, allowing automatic compressor and fan operation.	Engaged via "Em Heat" or "Emergency Heat" setting, bypassing compressor entirely.
System Lifespan	Heat pump compressors typically last 10-15 years with proper maintenance and usage.	Electric heating elements usually last 15-20 years but can burn out with frequent use.
Environmental Impact	Produces 1.5-2.5 tons of CO2 per year for typical homes, depending on grid mix.	Emits 3-5 tons of CO2 annually due to higher electricity consumption for same heat.
Installation Cost	Requires outdoor unit, refrigerant lines, and indoor coil, costing $4,000-$8,000 installed.	Adds only electric strip kit ($500-$1,500) if not already included with heat pump system.
Repair Frequency	Needs service every 1-2 years for refrigerant leaks, capacitor failures, or sensor issues.	Requires rare repairs, typically only when elements short out or relays stick closed.
Climate Suitability	Ideal for mild to moderate climates where winter lows stay above 25-30°F consistently.	Essential for cold climates with prolonged freezing temperatures below 20°F.
Smart Home Integration	Works with programmable thermostats to optimize efficiency based on occupancy and time.	Can be monitored via smart thermostats, but frequent use signals system inefficiency.
Backup Role	Functions as primary heat source, handling 80-90% of annual heating load in most homes.	Serves as secondary source, covering only 10-20% of heating needs during extreme cold.
Air Temperature	Delivers cooler supply air around 90-100°F, feeling less warm than gas furnace output.	Provides hotter supply air at 110-130°F, closely matching traditional furnace warmth.
Cycle Frequency	Runs in longer cycles of 15-30 minutes, maintaining steady temperature with fewer starts.	Cycles more frequently, often 5-10 minutes, due to rapid temperature overshoot.
Electrical Demand	Draws 15-30 amps at 240V for compressor and fans, depending on system tonnage.	Pulls 30-60 amps at 240V for heating elements, potentially requiring dedicated circuits.
Winter Performance	Maintains efficiency down to 25°F, but output drops as outdoor temperature decreases.	Provides full rated heat output regardless of outdoor temperature, down to -20°F.
User Confusion	Often misunderstood as slow or broken because supply air feels cooler than expected.	Frequently misused as "boost" mode, causing high bills when left on permanently.
Best-Fit Scenario	Choose for moderate climates with mild winters and consistent temperatures above freezing.	Choose for cold climates with frequent sub-freezing temperatures or unreliable heat pump operation.

What Is Heat?

Heat is the transfer of thermal energy between substances due to a temperature difference. It flows spontaneously from hotter objects to colder ones. Heat drives weather patterns, powers industrial processes, and enables cooking. Without heat transfer, life as we know it could not exist on Earth.

Definition of Heat

Heat is defined as energy in transit across a system boundary due solely to a temperature difference between the system and its surroundings. Measured in joules or calories, heat is not a property of matter but a process-dependent quantity. It ceases to exist once thermal equilibrium is reached.

Key Characteristics of Heat

Characteristic	What It Means in Practice
Direction of flow	Heat always moves from higher-temperature regions to lower-temperature regions until equilibrium is reached.
Measurement units	Quantified in joules (SI), calories, or British thermal units; one calorie equals 4.184 joules.
Transfer mechanisms	Moves via conduction through solids, convection through fluids, and radiation through empty space.
Temperature vs. heat	Temperature measures average kinetic energy; heat measures total transferred energy, not stored content.
State changes	Absorbed heat drives melting, vaporisation, and sublimation without raising temperature during phase transitions.
Specific heat capacity	Different materials require different energy amounts per degree change; water needs 4.18 J/g°C.
Latent heat	Hidden energy absorbed or released during phase changes; water's latent heat of vaporisation is 2,260 kJ/kg.
Conservation principle	Heat energy is never destroyed; it only converts to other forms like work or internal energy.
Perception vs. reality	Metal feels colder than wood at the same temperature because it conducts heat away faster.
Entropy connection	Heat transfer always increases total entropy, making it an irreversible process in isolated systems.

Common Examples of Heat

Solar radiation – the Sun emits heat via electromagnetic waves that travel 150 million kilometres to warm Earth's surface.
Boiling water – a stove transfers heat to a pot, raising water to 100°C at standard atmospheric pressure.
Human metabolism – cellular respiration releases heat continuously, maintaining body temperature near 37°C.
Volcanic activity – geothermal heat from Earth's core melts rock and drives magma to the surface.
Car engine combustion – burning fuel releases heat that expands gases to push pistons and create motion.
Electric heater – electrical resistance converts current into heat, warming rooms through convection and radiation.
Friction braking – kinetic energy converts to heat when brake pads press against rotating discs, slowing vehicles.
Microwave cooking – microwave radiation excites water molecules, generating heat inside food without heating the container.
Ocean currents – tropical heat absorbed by seawater transfers toward poles, moderating global climates.
Industrial smelting – blast furnaces generate extreme heat exceeding 1,500°C to extract iron from ore.

Advantages and Limitations of Heat

Advantages	Limitations
Enables cooking and food preservation, killing harmful bacteria through pasteurisation and sterilisation.	Heat engines waste roughly 60-70% of input energy as rejected heat, limiting overall efficiency.
Powers electricity generation in thermal plants, supplying about 60% of global electricity.	Heat loss through poorly insulated buildings accounts for up to 30% of residential energy consumption.
Drives essential industrial processes like metal forging, glass making, and chemical manufacturing.	Excess heat causes material degradation, reducing component lifespan in engines and electronics.
Enables weather circulation, distributing energy across the planet through atmospheric and oceanic movement.	Heat stress in urban areas raises temperatures 3-5°C above surrounding rural regions, worsening health risks.
Facilitates medical sterilisation, ensuring surgical instruments are free from infectious microorganisms.	Thermal pollution from power plants harms aquatic ecosystems by lowering dissolved oxygen levels.
Supports renewable geothermal energy, providing consistent, low-carbon baseload power in suitable regions.	Heat transfer is irreversible; recovering wasted heat for reuse requires additional energy input.
Enables refrigeration cycles that preserve food and medicines by actively removing heat from enclosed spaces.	High-temperature processes require expensive refractory materials that resist melting and thermal shock.
Drives distillation and desalination, producing clean drinking water from seawater or contaminated sources.	Uneven heat distribution causes thermal expansion, leading to warping, cracking, and structural failures.
Provides comfortable indoor environments through central heating systems in cold climates.	Combustion-based heat generation releases carbon dioxide and pollutants, contributing to climate change.
Enables phase-change energy storage, allowing concentrated solar plants to generate power after sunset.	Heat cannot be completely converted into work; the second law of thermodynamics imposes strict limits.

What Is Em Heat?

Em heat is the auxiliary electric resistance heating mode in a heat pump system. It activates when the outdoor unit cannot extract enough warmth, typically below freezing. Em heat provides backup warmth using electric coils, ensuring indoor comfort during extreme cold or defrost cycles.

Definition of Em Heat

Em heat, or emergency heat, is a secondary electric resistance heating function in heat pump systems. It bypasses the compressor and outdoor coil entirely, relying solely on electric heating strips inside the indoor air handler. This mode delivers rapid, reliable heat when outdoor temperatures drop too low for efficient heat pump operation.

Key Characteristics of Em Heat

Characteristic	What It Means in Practice
Electric resistance	Uses electric coils to generate heat directly, without refrigerant or compressor involvement.
Backup function	Activates automatically when the heat pump cannot meet the thermostat setpoint efficiently.
High energy cost	Consumes 2-3 times more electricity than a heat pump in normal heating mode for the same output.
Rapid warm-up	Produces heat immediately, unlike a heat pump that needs time to extract warmth from outdoor air.
Manual override	Can be selected manually on the thermostat, but this forces the compressor to shut down completely.
Defrost support	Provides supplemental warmth during the heat pump's periodic defrost cycles to prevent cold drafts.
Outdoor unit off	When em heat is active, the outdoor condenser fan and compressor stop running entirely.
Lower efficiency	Delivers only 1 unit of heat per 1 unit of electricity, versus a heat pump's 2-4 units.
Emergency only	Designed for short-term use during system failure or extreme cold, not as a primary heating source.
Thermostat indicator	Shows a dedicated "EM HEAT" or "AUX HEAT" light on the thermostat when this mode is engaged.

Common Examples of Em Heat

Heat pump failure - When the compressor stops working, em heat keeps the home warm until repairs are made.
Extreme cold snap - During sub-zero temperatures, em heat supplements the heat pump when outdoor coils freeze over.
Defrost cycle - Em heat activates briefly to prevent cold air from blowing into the house while the outdoor unit thaws.
Thermostat manual selection - A homeowner switches to em heat when they notice ice buildup on the outdoor unit.
New construction - Homes with heat pumps in cold climates often use em heat as a backup for below-freezing nights.
Multi-stage systems - In dual-fuel setups, em heat works alongside a gas furnace for the coldest winter days.
Mobile homes - All-electric heat pump systems in manufactured housing frequently rely on em heat during winter storms.
Smart thermostat alerts - Systems like Nest or Ecobee automatically engage em heat when the heat pump runs too long.
Rental properties - Landlords install em heat as a safety net for tenants who may not notice a failing heat pump.
Heat pump lockout - When outdoor temperatures drop below the manufacturer's minimum rating, em heat takes over completely.

Advantages and Limitations of Em Heat

Advantages	Limitations
Provides heat when the heat pump cannot operate due to extreme outdoor temperatures.	Operating costs are significantly higher, often doubling or tripling monthly electricity bills.
Delivers warm air immediately, eliminating the long wait associated with heat pump warm-up.	Offers lower efficiency, wasting energy compared to the heat pump's refrigerant-based heating.
Works reliably during compressor failure, keeping the home livable until professional repair arrives.	Can overheat small spaces if left on too long, leading to uncomfortable temperature swings.
Simple to activate with a single thermostat switch, requiring no special technical knowledge.	Forces the outdoor unit to remain idle, which can cause ice to accumulate on the coils.
Extends the lifespan of the compressor by reducing its workload during extreme cold events.	Produces drier air than a heat pump, potentially causing static electricity and dry skin.
Acts as a safety net during defrost cycles, preventing cold drafts from entering living spaces.	May trip circuit breakers in older homes due to the high electrical draw of heating coils.
Works independently of outdoor temperature, making it a dependable last-resort heating method.	Requires frequent filter changes because the electric coils attract dust and reduce airflow.
Can be paired with a smart thermostat for automatic activation during system performance issues.	Creates a noticeable electric burning smell during first use, which can alarm homeowners.
Offers consistent heat output regardless of outdoor weather conditions, unlike heat pumps.	Increases the risk of electrical fires if the wiring or breaker is undersized for the load.
Provides a clear diagnostic signal that the heat pump is struggling, prompting timely maintenance.	Leaves the system without cooling capability, so it cannot be used during summer emergencies.

Similarities Between Heat and Em Heat

Shared Aspect	How Heat and Em Heat Are Alike
Primary Purpose	Both Heat and Em Heat are designed to raise indoor temperatures for occupant comfort during cold weather.
Energy Source	Heat and Em Heat both rely on electricity as their primary input to generate thermal energy.
Heat Generation	Both Heat and Em Heat produce warmth through resistive electric coils that convert electrical energy into heat.
Output Type	Heat and Em Heat both deliver warm air via forced convection through vents or baseboard units.
User Control	Both Heat and Em Heat are regulated by thermostats that allow users to set desired temperature levels.
Zoning Ability	Heat and Em Heat both support independent room-by-room temperature control in multi-zone setups.
Installation Location	Both Heat and Em Heat are commonly installed in walls, floors, or ceilings for space-efficient operation.
Safety Features	Heat and Em Heat both include overheat protection and tip-over switches to prevent fire hazards.
Thermostat Compatibility	Both Heat and Em Heat work with standard low-voltage thermostats for straightforward integration.
Operating Voltage	Heat and Em Heat both typically operate on standard 240-volt residential circuits in North America.
Response Time	Both Heat and Em Heat provide near-instant warmth within minutes of activation due to direct resistive heating.
Maintenance Needs	Heat and Em Heat both require minimal upkeep, limited to periodic dusting and filter cleaning.
Lifespan Expectancy	Both Heat and Em Heat typically last 20-30 years with proper care and regular electrical inspections.
Cost Structure	Heat and Em Heat both have low upfront equipment costs but higher ongoing electricity expenses.
Efficiency Rating	Both Heat and Em Heat convert nearly 100% of consumed electricity into usable heat energy.
Environmental Impact	Heat and Em Heat both produce zero on-site emissions, relying on grid electricity for operation.
Noise Level	Both Heat and Em Heat operate silently during heating cycles, with only a faint click from the thermostat.
Air Circulation	Heat and Em Heat both naturally circulate air through convection without requiring additional fans.
Humidity Effect	Both Heat and Em Heat do not add moisture to the air, preserving existing indoor humidity levels.
Control Options	Heat and Em Heat both support programmable and smart thermostats for automated scheduling.
Building Codes	Both Heat and Em Heat must comply with the same electrical and building safety regulations.
Warranty Coverage	Heat and Em Heat both typically come with 5-10 year manufacturer warranties on heating elements.
Retrofit Feasibility	Both Heat and Em Heat can be added to existing homes without major ductwork or structural changes.
Thermal Mass	Heat and Em Heat both retain heat in surrounding materials for a short period after shutdown.
Seasonal Use	Both Heat and Em Heat are primarily used during winter months and can be turned off in summer.
Failure Mode	Heat and Em Heat both stop producing warmth entirely if the heating element burns out or breaks.
Electrical Protection	Both Heat and Em Heat require dedicated circuit breakers to prevent overloads and short circuits.
Comfort Consistency	Heat and Em Heat both maintain steady temperatures without noticeable hot or cold spots in a room.
Accessory Options	Both Heat and Em Heat support add-ons like timers, remote sensors, and mobile app controls.
Resale Value	Heat and Em Heat both add modest resale value to a home as functional, permanent fixtures.

Heat or Em Heat: Which Should You Choose?

The deciding variable is your outdoor temperature: choose Heat above 35°F and Em Heat below it. Heat mode uses the heat pump efficiently for mild weather, while Em Heat relies on the backup electric strip heater. Your choice directly impacts monthly energy costs and system longevity.

When to Use Heat

Choose Heat when outdoor temperatures stay above 35°F, which covers most of the year. Heat mode transfers warmth from outside air, costing roughly 2–3 times less than electric resistance heating. Use it for normal daily comfort, moderate climates, and routine thermostat settings to maximize efficiency.

When to Use Em Heat

Choose Em Heat when outdoor temperatures drop below 35°F, when ice covers the outdoor unit, or when the heat pump fails. Em Heat activates the electric strip heater, producing rapid warmth but consuming 2–3 times more electricity. Use it for emergency breakdowns, extreme cold snaps, or when frost prevents normal compressor operation.

Common Misconceptions About Heat and Em Heat

Common Myth	The Reality
Em Heat stands for emergency heat and only turns on during a fire or power outage.	Em Heat is a manual backup setting for heat pumps; it engages the electric resistance strips or furnace when the outdoor unit cannot keep up.
Heat mode and Em Heat mode produce identical warmth and use the same amount of electricity.	Heat mode runs the heat pump compressor for efficient warmth, while Em Heat bypasses the compressor and uses resistive coils, consuming 2-3 times more energy.
You should switch to Em Heat every winter to protect the heat pump from cold damage.	Modern heat pumps operate efficiently down to freezing or below; using Em Heat unnecessarily raises your utility bill and adds wear to the backup system.
Em Heat is the same as auxiliary heat that your thermostat selects automatically.	Auxiliary heat activates automatically during defrost cycles or rapid temperature drops, while Em Heat is a manual override that locks out the compressor entirely.
Leaving the thermostat on Em Heat all season keeps your home warmer than using Heat.	Em Heat only matches heat pump output while costing more per BTU; it never produces warmer air than a properly sized heat pump in normal conditions.
Heat mode will damage the outdoor unit if temperatures fall below 20 degrees Fahrenheit.	Heat pumps operate safely below 20°F; they lose efficiency but do not suffer damage, and the system's own defrost cycle protects the coils from ice buildup.
Em Heat is a separate heating system installed in addition to your main furnace.	Em Heat is not a separate appliance; it is a mode on your existing thermostat that activates the same backup heat strips or gas furnace already inside your system.
Switching between Heat and Em Heat frequently saves money because it rests the compressor.	Frequent manual switching forces the heat pump to cycle on and off, increasing wear and energy use; the thermostat handles transitions better than manual toggling.
If the outdoor unit is covered in ice, you must turn on Em Heat to melt it.	The heat pump runs its own defrost cycle automatically, briefly switching to cooling mode to warm the coils; Em Heat does not directly defrost the outdoor unit.
Em Heat produces hotter air from the vents, so it is the better choice for rapid warming.	Em Heat delivers air around 20-30°F warmer than heat pump air, but it warms the house slower overall because it lacks the compressor's higher total heat output.
Heat mode uses gas, while Em Heat uses electricity, so you should pick based on fuel prices.	Both Heat and Em Heat draw from the same power source in an all-electric heat pump; only dual-fuel systems switch between electricity and gas, and Em Heat never uses gas.
Turning the thermostat up 5 degrees on Heat will make the backup heat come on automatically.	Most thermostats activate auxiliary heat only when the temperature gap exceeds a set threshold (usually 2-3°F) or after a timed delay, not simply from a 5-degree adjustment.
Em Heat is required for heat pumps to work during winter; without it, the system will freeze.	Heat pumps provide primary heating all winter without Em Heat; the backup only assists during extreme cold or if the compressor fails, not for normal operation.
Heat mode and Em Heat mode both use the outdoor unit, so they perform identically in a blizzard.	Heat mode relies on the outdoor compressor to extract heat from outside air; Em Heat shuts the outdoor unit off and uses indoor resistance coils, which work in any weather.
Your thermostat's Em Heat setting is a safety feature that prevents electrical fires.	Em Heat is a convenience backup mode, not a safety mechanism; it increases electrical load on your panel and can trip breakers if the strips are oversized.
Heat pumps in Heat mode blow cold air when outside temperatures drop, so Em Heat fixes that.	Heat pumps blow cooler supply air (85-95°F) than furnaces, but it is still warm; Em Heat blows hotter air but does not fix the perceived draft, which is normal airflow.
You can run Heat and Em Heat at the same time to double your heating speed.	The thermostat locks out simultaneous operation; selecting Em Heat disables the compressor, so the two modes never run together in a standard single-stage system.
Em Heat is the same as setting your thermostat to "fan only" with extra heat.	Fan only circulates air without heating; Em Heat activates electric resistance coils or gas burners, producing real heat independent of the heat pump's compressor.
If your electricity bill spikes in winter, it is because you left Heat mode on instead of Em Heat.	Heat mode is the efficient option; a bill spike usually comes from auxiliary heat cycling on during defrost or from a dirty filter, not from using Heat mode.
Em Heat stands for "emergency melt heat" and is used to melt snow off the outdoor unit.	Em Heat is an abbreviation for emergency heat, a backup heating mode; it does not melt snow off the outdoor coil and has no connection to defrosting.
Heat mode is only for mild weather, and Em Heat is the correct setting for below-freezing temperatures.	Heat mode works at all temperatures down to the unit's rated minimum (often -5°F to 20°F); Em Heat is only for compressor failure or extreme cold beyond that rating.
Turning on Em Heat will make your heat pump last longer because the compressor rests.	Em Heat shifts workload to resistive strips, which have a shorter lifespan than compressors; overusing Em Heat can cause more wear on relays and breakers.
Heat mode and Em Heat are interchangeable terms used by HVAC technicians.	Technicians distinguish them clearly: Heat mode uses the heat pump cycle, while Em Heat is a manual backup that bypasses the compressor for emergency situations.
If your home feels cold, switching to Em Heat will always solve the problem faster.	Em Heat only helps if the heat pump is undersized or failing; if the issue is poor insulation or a thermostat setback, Em Heat wastes energy without fixing the root cause.
Em Heat is a modern feature found on all thermostats, including non-heat-pump systems.	Em Heat appears only on heat pump thermostats; gas furnaces, boilers, and electric furnaces do not have an Em Heat setting because they lack a compressor to bypass.
Running Em Heat during a power outage keeps your house warm because it uses no electricity.	Em Heat requires electricity for the blower fan and resistance coils; during a power outage, it does not work unless you have a generator or battery backup.
Heat mode uses the outdoor unit only, while Em Heat uses the indoor unit only, so they are opposites.	Heat mode uses both indoor and outdoor coils to transfer heat; Em Heat uses only indoor resistance elements, but both modes share the same indoor blower and ductwork.
Setting the thermostat to Em Heat when you leave for vacation prevents pipes from freezing.	Em Heat does not protect pipes better than Heat mode; it just costs more. A low temperature setting on Heat mode is sufficient and more economical for freeze protection.
Em Heat is the recommended setting for the entire winter in northern climates.	Northern homeowners should rely on Heat mode for normal winter operation; Em Heat is reserved for compressor failure or temperatures below the unit's rated minimum, not routine use.
Heat mode and Em Heat both trigger the same defrost cycle on the outdoor coil.	Defrost cycles run only in Heat mode; Em Heat disables the outdoor unit entirely, so no defrost occurs, which is why ice can build up if you leave Em Heat on too long.

Conclusion

Difference Between Heat and Em Heat comes down to backup versus primary operation. Heat uses the compressor for efficient warmth; Em Heat relies on electric strips for emergency situations. Choose Heat for daily comfort and lower costs. Choose Em Heat only when the heat pump fails or ice threatens the system.

FAQs on Difference Between Heat and Em Heat

What is the main difference between Heat and Em Heat?: The main difference is that Heat uses your heat pump to extract warmth from outdoor air, while Em Heat activates the electric resistance backup heating strips inside your indoor unit.
Which is better, Heat or Em Heat, for warming a home?: Heat is better for normal winter conditions because it is far more energy-efficient, whereas Em Heat is better only as an emergency backup when the outdoor unit fails or is frozen.
Does using Em Heat cost more than using Heat?: Yes, using Em Heat costs significantly more because electric resistance strips produce roughly three times less heat per dollar compared to the heat pump's efficient refrigerant cycle.
Is it safe to run Em Heat for an extended period?: Yes, it is safe to run Em Heat for an extended period because it is designed for continuous operation, but doing so will cause a substantial spike in your electricity bill.
Can Em Heat be used with any type of thermostat?: No, Em Heat can only be used with a thermostat that has a dedicated emergency heat terminal and a system configured with electric backup heat strips.
What is a common beginner mistake with Heat and Em Heat settings?: A common beginner mistake is manually switching to Em Heat during a cold snap, which forces expensive backup strips to run instead of letting the heat pump work efficiently.
Are Heat and Em Heat interchangeable settings on a thermostat?: No, Heat and Em Heat are not interchangeable because Heat relies on the outdoor compressor, while Em Heat bypasses that compressor entirely and uses only the indoor electric strips.
When should a homeowner actually switch the thermostat to Em Heat?: You should switch to Em Heat only when the outdoor heat pump unit is broken, iced over, or not producing warm air, and you need heat while waiting for a repair.
Can I switch from Heat to Em Heat while the system is running?: Yes, you can switch from Heat to Em Heat while the system is running because the thermostat will safely deactivate the compressor and activate the backup strips within a minute.
Does Em Heat damage the heat pump system over time?: No, Em Heat does not damage the heat pump system itself, but overusing it wastes energy and can shorten the lifespan of the electric heating elements.