A sudden spike in your winter energy bill is often the first sign that something is wrong with your heating system. Before you blame the cold weather, take a look at your thermostat. If you’ve been using the Emergency Heat setting, you’ve likely found the culprit. This backup feature is one of the most misunderstood parts of a heat pump system, and using it unnecessarily can double or even triple your heating costs. It’s not a button for an extra blast of warmth; it’s a last resort. This guide will explain what this setting does and how to use it correctly to protect your wallet.
Key Takeaways
- Emergency heat is a manual override, not a comfort setting: Only switch it on if your heat pump has completely failed. For extra cold days, trust your system to automatically use its more efficient auxiliary heat to keep you warm.
- It’s a temporary fix with a high price tag: Running your emergency heat uses a massive amount of electricity compared to your heat pump, which can cause a serious shock on your next utility bill.
- Treat it as a signal to call for service: If you find yourself needing to use the emergency heat, it means your primary system is broken. Your next step should always be to schedule a professional repair to fix the root cause.
What Is Emergency Heat, Anyway?
If you have a heat pump, you’ve probably seen the “Emergency Heat” or “EM Heat” setting on your thermostat and wondered what it’s for. Think of it as your home’s backup heating system. It’s designed to take over when your primary system—the heat pump—can’t keep up, either because of extremely cold weather or a mechanical issue. When you manually switch to this setting, you’re telling your system to bypass the heat pump entirely and rely on a secondary source, which is usually an electric resistance heating strip (similar to the coils in a toaster). While it’s a crucial feature for staying warm during a true heating failure, it’s not meant for everyday use. Understanding how and when to use it is key to keeping your home comfortable without sending your energy bills through the roof.
Emergency Heat vs. Auxiliary Heat: What’s the Difference?
It’s easy to confuse emergency heat with auxiliary heat, but they play very different roles. Auxiliary heat, or “Aux Heat,” is your heat pump’s automatic helper. On chilly days, when your heat pump needs a little extra help to reach your desired temperature, the auxiliary heat kicks in automatically to assist. You don’t have to do anything. Emergency heat, on the other hand, is a manual setting. You should only turn it on when your heat pump has stopped working completely. Switching to EM heat turns off your heat pump and relies solely on the less efficient backup system. So, think of auxiliary heat as a teammate, and emergency heat as the backup you call in when your main player is out of the game.
How It Works With Your Heat Pump
Your heat pump is an incredibly efficient piece of equipment that works by pulling heat from the outside air and moving it into your home. However, when the outdoor temperature drops, typically below 35°F, there’s less heat available in the air for the unit to extract. This is when the system starts to work harder and may need help. If the outdoor coil gets too cold, it can frost over. To deal with this, your system will enter a defrost cycle, temporarily switching to its cooling mode to warm the outdoor coils while the auxiliary heat comes on to keep your home warm. This is a normal and necessary function for any residential HVAC system with a heat pump.
When Your System Switches on Its Own
Don’t be alarmed if you see the “Aux Heat” indicator light up on your thermostat. This is completely normal and means your system is working exactly as it should. Your system will automatically switch to auxiliary heat for a few common reasons. The most frequent one is during a defrost cycle, as mentioned above. It will also turn on if there’s a sudden, large difference between the room temperature and the thermostat setting—for instance, if you raise it by more than a few degrees at once. Finally, it will activate during prolonged periods of very cold weather when the heat pump simply can’t generate enough warmth on its own. Regular check-ups from our service maintenance programs can ensure this process runs smoothly.
When Should You Actually Use Emergency Heat?
That little “EM Heat” switch on your thermostat can be tempting when the temperature plummets, but it’s not a button for extra warmth. Think of it as the spare tire for your HVAC system—it’s there for true emergencies only, not for everyday driving. Using it correctly can save you from a chilly house and a sky-high energy bill. Let’s walk through the exact situations when you should—and shouldn’t—flip that switch.
Real Emergencies: When to Flip the Switch
The only time you should manually turn on your emergency heat is when your heat pump has completely stopped working. This is your “worst-case scenario” option. If your system is blowing cold air or has shut down entirely due to a malfunction, the emergency heat will provide a temporary source of warmth until a technician can arrive. It’s a bridge to keep your home and pipes from freezing. Once you’ve switched it on, your next step should be to call for a professional heat pump repair to diagnose and fix the root problem.
Warning Signs Your Heat Pump Needs Help
Your heat pump will often give you clues that something is wrong before it fails completely. If you notice your system is constantly running or the “AUX” heat light is on more than it should be (especially on milder days), it’s a sign the main unit is struggling. Other red flags include strange grinding or squealing noises or a sudden, unexplained spike in your energy bills. These are all indicators that your system is working too hard and needs attention. Catching these issues early with regular maintenance can often prevent you from needing the emergency heat setting in the first place.
When to Leave It Off (Even When It’s Cold)
It’s a common myth that you should switch to emergency heat just because it’s freezing outside. Don’t do it! Your heat pump is designed to handle cold weather. When the temperature drops so low that the heat pump can’t pull enough warmth from the outside air, its auxiliary heat (AUX) will automatically turn on to assist. This is a normal, efficient part of its operation. Manually switching to emergency heat bypasses this smart function and forces your system into its least efficient mode. Trust your thermostat to manage the auxiliary heat on its own.
The Risk of Leaving It On Too Long
Running your emergency heat is incredibly expensive. It works by activating electric resistance coils—similar to the ones in a toaster or a space heater—to generate warmth. This method uses a massive amount of electricity compared to your heat pump, which simply moves heat from one place to another. Leaving it on for an extended period will cause a serious shock when you get your next utility bill. If you find yourself needing to use it, think of it as a very temporary fix and get a professional evaluation as soon as possible to avoid the high cost.
How Emergency Heat Impacts Your Wallet
Let’s talk about the bottom line. While emergency heat is a great safety net, relying on it for any length of time can do some serious damage to your budget. It’s designed for true emergencies, not as a primary heat source, and your utility bill will quickly reflect that. Understanding the financial side of things can help you make smarter decisions when the temperature drops and you’re tempted to flip that switch. Think of it as a spare tire for your car—it’ll get you where you need to go, but you wouldn’t want to drive on it for a week. The sticker shock from an energy bill after using emergency heat is real, and it’s often the first clue homeowners have that their heat pump isn’t working correctly. It’s a costly signal that your system needs professional attention. This section will break down exactly why it’s so expensive, what you can expect to see on your bill, and the long-term financial impact of depending on this backup feature. Knowing these details will not only save you money but also help you keep your entire heating system in better shape for years to come. It’s all about being prepared and knowing when to call for help instead of pushing a button that offers a temporary—and expensive—fix.
How Much More Energy Does It Use?
The short answer is: a lot. Emergency heat typically uses electric resistance coils to generate heat, which is a far more energy-intensive process than how your heat pump normally operates. A heat pump’s job is to move heat from one place to another, which is incredibly efficient. Your emergency heat system, on the other hand, has to create heat from scratch. As one expert puts it, running emergency heat is very expensive because these backup systems use significantly more energy than a properly working heat pump. This is why it’s crucial to have your residential HVAC system checked if you find yourself needing it.
What to Expect on Your Next Energy Bill
If you’ve had to run your emergency heat for more than a few hours, brace yourself for your next energy bill. It’s not an exaggeration to say it can double or even triple your typical heating costs for that period. Using emergency heat will make your electric bill much higher than using the standard heat pump mode. This is often the first sign homeowners notice that something is wrong with their system. If you get a bill that seems unusually high, think back to whether your emergency heat was running. It’s a clear indicator that your primary system isn’t pulling its weight and needs a professional diagnosis.
Why It’s Less Efficient Than Your Heat Pump
The difference in efficiency is stark. Your heat pump is a master of leverage, often operating at 300% to 400% efficiency because it transfers existing heat instead of creating it. Emergency heat, by contrast, is only 100% efficient. That means for every one unit of electrical energy it consumes, it produces exactly one unit of heat. While that might sound okay, it pales in comparison to your heat pump’s ability to move three or four units of heat for the same single unit of energy. This fundamental difference is why your heat pump is the hero of your winter energy bills, and emergency heat is the expensive backup player.
The Long-Term Cost of Relying on It
Relying on emergency heat is a costly mistake. It’s meant for worst-case scenarios when your heat pump is broken or during extreme, prolonged cold snaps where it can’t keep up. Running your home on emergency heat is incredibly expensive compared to using your heat pump. It also puts a strain on your electrical system and can mask underlying problems that could get worse over time. Instead of using it as a crutch, treat it as a signal to call for help. Investing in regular upkeep through service maintenance programs can prevent the issues that force you to use emergency heat in the first place, saving you a fortune in the long run.
Busting Common Emergency Heat Myths
The emergency heat setting on your thermostat can feel like a mystery. When do you use it? What does it even do? This confusion has led to a lot of myths that can end up costing you money and putting unnecessary strain on your HVAC system. Many homeowners see that little “EM Heat” switch and assume it’s a turbo button for extra warmth on the coldest days, but that’s not its purpose at all. Understanding the difference between how your heat pump normally operates and what emergency heat is for is key to keeping your home comfortable and your energy bills in check. Let’s clear up some of the most common misconceptions so you can feel confident managing your home’s heat this winter and know exactly when—and when not—to flip that switch.
Myth #1: Flip It On Just Because It’s Freezing
It’s a common mistake to think that when the temperature really plummets, you should switch on the emergency heat. The truth is, your heat pump is designed to handle cold weather. The “emergency” in emergency heat means just that—it’s for true emergencies. You should only manually turn on the EM heat setting if your primary heat pump has stopped working or is seriously malfunctioning. For regular cold days, trust your system to do its job. It will automatically use its auxiliary heat strips as needed to supplement the heat pump without you having to do a thing.
Myth #2: It Heats Your Home Faster
If you’re feeling chilly, it can be tempting to flip the emergency heat switch, thinking it will give your system a quick boost. Unfortunately, that’s not how it works. Emergency heat won’t warm your home any faster than your heat pump running correctly. It’s simply a backup system, like a spare tire for your car. It’s meant to get you through a worst-case scenario—like a broken heat pump—until a professional can arrive. Relying on it will only lead to a much higher electric bill, as it’s a far less efficient way to generate heat.
Myth #3: Ice on Your Outdoor Unit Is an Emergency
Seeing ice or frost on your outdoor heat pump unit can be alarming, but it’s usually not a cause for panic. It’s perfectly normal for a heat pump to build up some frost or ice during winter operation. Your system has a built-in defrost mode to handle this, which might produce a puff of steam that looks like smoke. Your thermostat is smart enough to activate the auxiliary heat automatically to keep you warm while the outdoor unit defrosts. If, however, your unit is completely encased in a thick block of ice, that points to a bigger issue, and it’s time to call for HVAC service.
Myth #4: It’s a Long-Term Fix
Think of emergency heat as a temporary patch, not a permanent solution. Using it for more than a day or two is a sign that your heat pump needs immediate attention. Running your home on emergency heat is incredibly expensive compared to using your heat pump, and it doesn’t solve the root problem. If you find yourself needing to use it, your next step should be to schedule a repair. Regular check-ups through a service maintenance program can help you avoid these situations altogether by catching potential issues before they become emergencies.
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Frequently Asked Questions
Okay, give it to me straight: what’s the real difference between “Aux Heat” and “Emergency Heat”? Think of auxiliary heat as your system’s automatic assistant. When it gets really cold outside, your heat pump might need a little help, and the “Aux Heat” will kick on by itself to give it a hand. Emergency heat, on the other hand, is a manual override. You should only turn it on if your heat pump has completely failed, as it shuts the main system off and relies entirely on the less efficient backup heating strips.
My “Aux Heat” light keeps turning on. Should I be worried? Not usually! Seeing the “Aux Heat” light come on is typically a sign that your system is working exactly as it should. It will activate during very cold weather, when your system runs a normal defrost cycle, or if you raise the thermostat by several degrees at once. If you notice it’s on constantly, even on milder days, that could be a sign your heat pump is struggling and it’s a good idea to have a professional take a look.
What are the clear signs that my heat pump is failing and I actually need to use the emergency setting? You should only flip the emergency heat switch if your heat pump has truly stopped working. The most obvious signs are if the system is blowing cold air instead of warm, making loud grinding or squealing noises, or has shut down completely and won’t turn back on. In those situations, turn on the
How can I avoid having to use my emergency heat in the first place? The single best way to prevent a heating emergency is with consistent, professional maintenance. Having your system inspected and tuned up regularly helps technicians catch small issues, like worn-out parts or low refrigerant, before they can cause your entire heat pump to fail. This proactive approach keeps your system running efficiently and reliably, so you never have to depend on that expensive backup.
Seriously, how bad will my electric bill be if I use emergency heat? It can be pretty shocking. Because emergency heat uses electric resistance strips—which consume a massive amount of energy to create heat from scratch—it can easily cause your heating costs to double or even triple. Your heat pump is far more efficient because it moves existing heat. Think of emergency heat as a very expensive temporary solution that signals it’s time to get your primary system fixed as soon as possible.