Reviewed by Zack W. Grossenburg · General Manager HVAC Master · Plumbing Master · EPA 608 · Daikin DCP
The Temptation of the Switch During Early-Fall Cold Snaps
In our years of providing HVAC services across Leavenworth, KS, our team at Mr. Breeze Heating & Cooling has noticed a distinct pattern when the first September early-fall cold snaps arrive: homeowners are suddenly focused on understanding your thermostat's emergency heat setting before you need it. The temperature drops rapidly across the Midwest, and your living room feels unusually chilly. You walk over to the thermostat, see the indoor temperature lagging behind your target, and spot that switch labeled "Em Heat." It is incredibly tempting to flip it, assuming it will force the system to work harder and warm your house up faster. This is a common situation we see many homeowners face as the seasons change, but treating this setting as a shortcut to comfort usually leads to massive energy inefficiency.
Before the real winter weather sets in, getting a professional assessment is crucial. If you want to ensure your system is ready for the changing seasons, scheduling heat pump and HVAC maintenance in Leavenworth is the smartest first step. A tune-up ensures everything operates as it should, so you are not left guessing when the temperature drops.
Sudden September and October temperature drops in our regional climate often trigger a kind of panic-use of the thermostat. When the house is cold, you want a quick fix. However, the concrete problem here is a widespread misconception about what that switch actually does. You are faced with a decision point: do you manually override the system during a cold snap, or do you let the standard heat pump operations handle the load? Choosing the manual override without understanding its mechanical function bypasses your system's efficiency entirely, forcing it to consume drastically more power for the exact same amount of warmth.
The 'Turbo Button' Myth: What the Indicator Actually Means
The Problem: A pattern we see often during our fall maintenance visits is that when the house feels uncomfortably cold, human psychology drives us to look for an immediate solution. We are accustomed to devices having a "boost" or "max" setting. When you see the 'Em Heat' thermostat indicator, it is easy to assume it acts like a turbo button for your heating system, designed to blast hot air and bring the temperature up in record time. Homeowners frequently switch this on, expecting a sudden surge of intense heat to flood through their vents.
The Cause: This myth persists because the air coming out of the vents during emergency operation often feels slightly warmer to the touch than the air produced during standard heat pump operation. Standard heat pumps provide a steady, consistent warmth that builds gradually, which can feel less dramatic than a traditional furnace. Because the emergency setting activates electric resistance strips—which get very hot, very quickly—it creates the illusion that the system is simply working "better" or "faster." In reality, heat pumps do not have a turbo function for standard heating.
The Solution: You need to understand what that indicator is actually signaling. When the 'Em Heat' light is on, it is not telling you the system is working harder; it is telling you the primary heating system has been completely shut down. The indicator is a warning that you are now relying 100% on a secondary, highly inefficient backup heat source. Your heat pump is designed to reach the set temperature efficiently without manual intervention. Trusting the system to operate as designed is the best way to maintain both comfort and energy efficiency.
Auxiliary Heat vs. Emergency Heat: Decoding Your Thermostat
To truly master your home's climate control, you must clearly distinguish between the automatic auxiliary function and the manual emergency override. Confusing these two settings is the root cause of many winter HVAC issues our technicians respond to. While they both utilize the same backup heating elements inside your air handler, how and when they activate are completely different.
| Feature | Auxiliary Heat (Aux) | Emergency Heat (Em Heat) |
|---|---|---|
| Activation Method | Automatic (controlled by the system) | Manual (switched by the homeowner) |
| Outdoor Unit Status | Running (working together) | Completely locked out / shut down |
| Primary Purpose | To assist the heat pump during extreme cold or defrost cycles | To provide heat only when the outdoor unit is broken |
| Efficiency Level | Moderate (balances heat transfer with backup power) | Very Low (relies entirely on high-energy resistance strips) |
How Auxiliary Heat Operates Automatically
Our technicians always remind customers that auxiliary (Aux) heat is an automatic function built into your system's logic board. It is triggered by the system's internal sensors, not by the homeowner. When the outside air drops to a certain temperature (usually around freezing), the heat pump may struggle to extract enough heat to maintain your indoor temperature. When this happens, the system automatically turns on the electric resistance strips to give the heat pump a temporary boost.
During this process, the auxiliary heat operates in tandem with the outdoor unit. They work together. Once the target indoor temperature is reached, the auxiliary heat turns off automatically, and the heat pump resumes its highly efficient solo operation. You might also notice this setting activate during a defrost cycle. If you are wondering why your heat pump might blow cool air during its defrost cycle, it is because the system briefly reverses itself to melt ice, and the auxiliary heat kicks in to keep your home warm while this happens.
How the Manual Override Changes System Behavior
Emergency heat, on the other hand, requires physical interaction with the thermostat. When you move the switch to this setting, you are actively changing the system's operational parameters. The most critical change is that this manual override shuts down the outdoor unit entirely. The compressor stops running, the outdoor fan stops spinning, and the system stops attempting to transfer heat from the outside air.
Instead, the system relies 100% on the secondary heating elements located in the indoor air handler. You are bypassing the primary technology that makes a heat pump efficient and turning your central heating system into a giant, electrically powered space heater.
The Mechanical Reality: How Emergency Heat Actually Works
To appreciate why the manual override should be used sparingly, it helps to understand the mechanical reality of how these systems generate warmth. Heat pumps are celebrated for their efficiency because they do not technically generate heat; they move it. According to U.S. Department of Energy (DOE) guidelines, heat transfer is significantly more energy-efficient than creating heat from scratch.
Here is exactly what happens mechanically when you flip that switch:
- The Signal is Sent: Your thermostat sends a direct 24-volt signal to the indoor air handler, bypassing the logic board's normal staging process.
- The Outdoor Unit is Locked Out: A relay prevents the outdoor compressor and fan from receiving power. The highly efficient process of extracting ambient heat from the outside air ceases completely.
- Electric Strips Activate: Power is routed directly to the electric resistance heating strips inside your ductwork. These function very much like the glowing coils inside a giant toaster or a hairdryer.
- The Blower Distributes Air: The indoor blower motor pushes air over these red-hot metal strips, warming the air before forcing it through your home's vents.
Because the system is now bypassing the outdoor unit entirely, it must work significantly harder to produce the same amount of warmth. Standard heat pump operation can deliver up to three times more heat energy to a home than the electrical energy it consumes. Electric resistance heating, however, operates at a one-to-one ratio. For every unit of electricity consumed, only one unit of heat is produced. This mechanical shift completely alters the energy profile of your home.
The Financial Impact of Misunderstanding Your Thermostat
The consequences of leaving this setting on unnecessarily are severe, primarily when it comes to your energy consumption. Because electric resistance heating consumes significantly more energy than standard heat transfer, relying on it as your primary heat source will cause your power meter to spin rapidly.
The phenomenon of bill shock: Every year, our team at Mr. Breeze Heating & Cooling hears from homeowners who experience severe "bill shock" after a chilly early fall. They flip the switch during a cold snap, the house warms up, and they simply forget to switch it back to the normal heating mode. They leave it on for days or even weeks. While the house may feel perfectly warm and comfortable, the system is operating at its lowest possible efficiency behind the scenes. When the utility statement arrives the following month, the dramatic spike in energy usage is often a very unpleasant surprise.
At Mr. Breeze Heating & Cooling, our commitment is to help local homeowners maximize comfort while avoiding unnecessarily high utility usage through proper education. We want you to know that standard operation is more than sufficient for most early-fall temperature drops. Your heat pump is engineered to handle these temperature swings without needing expensive backup power. If you suspect your system cannot keep up without the backup strips, it is time to call our team for professional HVAC repair services rather than relying on a costly manual override.
The Only Time You Should Actually Use Emergency Heat
If this setting is so inefficient, why does it exist at all? It exists as a safety net. There is a definitive, easy-to-understand rule for when you should touch this switch on your thermostat.
The Golden Rule: You should only use the emergency setting when the outdoor unit is completely broken, physically damaged, or encased in a solid block of ice that prevents the fan blades from turning.
Total heat pump failure is rare, but our dispatchers do receive those calls. For instance, one local homeowner reached out to our team when their entire heating and cooling system failed unexpectedly. Our technician arrived and discovered a broken low voltage wire and a blown fuse. Good diagnostics allowed us to quickly repair the identified issues, and the system was fully repaired within 90 minutes of the initial call. During that 90-minute wait, using the manual backup setting would have been the perfect way to keep the home comfortable.
This setting is designed solely to keep your pipes from freezing and to keep your home livable while you are waiting for professional repair. It is a bridge to get you through a crisis, not a long-term heating strategy. If you are ever forced to use this setting because your standard heat pump is failing, you should immediately call for professional diagnostics.
Pre-Season Preparation: Getting Your Heat Pump Ready
The best way to avoid a mid-winter crisis is through proactive, pre-season preparation. Emphasizing education before winter actually arrives ensures you understand your equipment and trust it to perform. In our extensive experience servicing homes in Leavenworth KS, where we experience freezing winter temperatures, backup systems absolutely must be ready. This makes fall preparation crucial.
Routine servicing protects your equipment: A comprehensive fall tune-up ensures that both the standard heat transfer mechanisms and the backup electric strips are functioning correctly. One of our technicians will test the reversing valve, check the refrigerant charge, and sequence the backup heaters to ensure they activate properly when the automatic auxiliary mode calls for them.
The value of professional guidance: Having a professional explain proper system operation and thermostat settings during a tune-up is invaluable. If your system is aging and struggling, we can help you plan your next steps. Another local customer recently realized their old unit needed replacement before the extreme weather hit. Our team at Mr. Breeze Heating & Cooling replaced the AC and heating unit quickly and politely, and the new system has been functioning without issues, providing reliable comfort without the need for manual overrides. As an added benefit, upgrading to a qualifying high-efficiency heat pump may make you eligible for federal tax credits or local utility incentive programs (we always advise readers to verify current programs with their utility or a tax professional). If you need HVAC repairs in Lansing or the surrounding areas, addressing lingering system concerns during the early fall transition period is always better than waiting for a breakdown in December.
Protect Your Home and Your Wallet This Winter
Understanding your thermostat settings is your best defense against high utility bills and unnecessary wear and tear on your HVAC equipment. Remember the definitive rule: the manual override setting is strictly for total system failure, not for a quick boost of warmth on a chilly autumn morning. By letting your heat pump operate normally, you harness its incredible efficiency. We strongly encourage you to schedule a pre-season check with our team to ensure your system is ready for the colder months, giving you total peace of mind when the real winter weather finally arrives.
Frequently Asked Questions
When should I turn on emergency heat?
You should only turn on this setting if your outdoor heat pump unit has completely failed, is physically damaged, or is covered in solid ice that prevents it from operating. It is designed to act as a temporary safety net to keep your home warm while you wait for an HVAC technician to arrive. Under normal weather conditions, even during extreme cold snaps, you should leave your thermostat in its standard heating mode.
Does emergency heat use more electricity?
Yes, it uses significantly more electricity than standard heat pump operation. Because it bypasses the energy-efficient process of transferring heat from the outside air, it relies entirely on electric resistance strips, which draw a massive amount of power. Running this setting continuously will result in a dramatic spike in your monthly utility consumption.
What is the difference between aux and emergency heat?
Auxiliary (Aux) heat turns on automatically when your heat pump needs a temporary boost during very cold weather or a defrost cycle, working alongside the outdoor unit. The emergency setting is a manual switch that you must turn on yourself, and it completely shuts down the outdoor unit. Aux heat is a normal part of system operation, while the manual override is strictly for system failures.
How long can you run emergency heat safely?
You can safely run the setting for as long as it takes a professional technician to arrive and repair your outdoor unit, which is typically a few days at most. The internal components are designed to handle the load, so it is not a safety hazard to your home. However, running it for extended periods is highly discouraged due to the extreme energy consumption it requires.
Why does my thermostat say emergency heat?
If your thermostat says this, it means the manual override switch has been activated, and your outdoor heat pump is currently locked out of operation. If you did not turn it on yourself, someone else in the home may have accidentally flipped the switch or adjusted the setting. You should switch it back to standard heating mode immediately unless your outdoor unit is broken.
Will emergency heat damage my heat pump if left on?
Leaving it on will not directly damage the indoor air handler or the backup heating strips, as they are designed to run when needed. It also will not damage the outdoor unit, because the outdoor unit is completely shut off in this mode. The "damage" will primarily be to your utility bill, as the system will consume a vast amount of electricity to maintain the temperature in your home.