You’ve noticed “Em Heat” or “Emergency Heat” on your thermostat and wondered whether you should use it, or maybe it turned on by itself and your energy bill spiked. Understanding what emergency heat actually does can save you money, prevent damage to your heating system, and help you make better decisions when your home feels uncomfortably cold.
This article explains how emergency heat works, when you truly need it, why it costs so much to run, and what steps you can take to avoid using it unnecessarily while keeping your home comfortable through winter.
What Is Emergency Heat on a Thermostat?
Emergency heat is a backup heating mode on heat pump systems that bypasses the outdoor unit and relies entirely on electric resistance heating inside your home. It’s designed for situations when your heat pump fails or cannot function properly, providing warmth through less efficient electric coils that heat air directly rather than transferring heat from outside.
How Emergency Heat Differs from Normal Heating
Most modern homes with heat pumps use a two-stage heating process. Your heat pump normally extracts warmth from outdoor air and moves it inside, which works efficiently even in cold weather.
When you switch to emergency heat, you’re telling the system to skip the heat pump entirely. The backup electric resistance coils take over completely, heating your home the same way a toaster or space heater works.
This difference matters because heat pumps can produce three units of heat for every unit of electricity they consume. Emergency heat produces only one unit of heat per unit of electricity, making it two to three times more expensive to operate.
When Emergency Heat Turns On Automatically
Some thermostats activate emergency heat without your input when outdoor temperatures drop below a certain threshold. This typically happens when the system detects that the heat pump cannot keep up with your temperature setting.
You might also see emergency heat kick in during the defrost cycle. When frost builds up on the outdoor unit, the system temporarily reverses to melt the ice, and backup heat prevents cold air from blowing through your vents during this process.
If emergency heat runs frequently or stays on for extended periods, your heat pump may need professional attention. Constant reliance on backup heat usually signals a refrigerant leak, a failing compressor, or incorrectly configured thermostat settings.
When You Should Manually Use Emergency Heat
You should only switch to emergency heat mode when your heat pump has completely stopped working. If you hear unusual grinding noises, notice ice coating the entire outdoor unit, or feel no warm air coming from vents even though the system runs, emergency heat can keep your family comfortable until a technician arrives.
Think of emergency heat as a temporary safety net, not a daily heating option. It exists to prevent frozen pipes and dangerously cold indoor temperatures during equipment failure, especially overnight or during holidays when repair services may not be immediately available.
Do not use emergency heat simply because it’s very cold outside. Modern heat pumps work effectively in temperatures well below freezing, and switching to emergency heat wastes money without providing additional comfort.
Why Emergency Heat Costs So Much to Run
Electric resistance heating converts electricity directly into heat with no multiplier effect. Every kilowatt of electricity produces only one kilowatt of heat.
A typical home running on emergency heat might use 15 to 25 kilowatts per hour, compared to 3 to 5 kilowatts for normal heat pump operation. If your electricity costs $0.12 per kilowatt-hour, emergency heat could add $30 to $50 per day to your utility bill.
Many people discover they’ve been running emergency heat accidentally after receiving a shocking electric bill. If your monthly heating cost suddenly doubles or triples, check your thermostat setting immediately.
Common Mistakes That Waste Money and Comfort
The most expensive mistake is confusing emergency heat with auxiliary heat. Auxiliary heat works alongside your heat pump to provide extra warmth on very cold days, then shuts off when your heat pump catches up. Emergency heat replaces your heat pump entirely and runs continuously until you manually turn it off.
Some people switch to emergency heat thinking it will warm the house faster. It won’t. Emergency heat and auxiliary heat produce the same amount of warmth, but emergency heat costs far more because it never allows your efficient heat pump to share the workload.
Another common error is leaving emergency heat on after the repair technician fixes your system. Always return your thermostat to its normal heating mode once your heat pump works properly again.
How to Tell If Your System Is Using Emergency Heat
Most thermostats display “EM Heat,” “Emergency Heat,” or a red indicator light when this mode is active. Check your thermostat screen and user manual to identify how your specific model shows this status.
You can also step outside and look at your heat pump unit. If the fan isn’t running and you don’t hear the compressor, but your home is still heating, you’re likely using emergency heat.
Your utility usage provides another clue. Many electric companies offer apps or online portals showing daily energy consumption. A sudden spike without a corresponding change in your routine often means emergency heat has been running.
What to Do If Emergency Heat Turns On
First, check whether you accidentally switched the thermostat to emergency heat mode. Many thermostats require you to press a specific button or move a switch to activate this setting, but it’s easy to do by mistake.
If you didn’t manually activate it, go outside and examine your heat pump. Clear away any snow, ice, leaves, or debris blocking the unit. Make sure nothing obstructs airflow around the equipment.
Listen for unusual sounds like grinding, squealing, or loud rattling. Look for ice buildup that covers more than just the coils. These signs indicate you need professional repair, and you should keep emergency heat on only until the technician arrives.
If everything appears normal outside but emergency heat keeps running, your thermostat settings may need adjustment. Consult your system’s manual or contact your HVAC company to verify that your heat pump and thermostat are configured correctly for your climate.
Preventing Unnecessary Emergency Heat Use
Regular maintenance keeps your heat pump running efficiently and reduces the chances you’ll need emergency heat. Schedule professional service each fall to clean coils, check refrigerant levels, test electrical connections, and ensure all components work properly.
Set your thermostat to a consistent temperature rather than making large adjustments throughout the day. Dramatic temperature swings force your system to work harder and may trigger auxiliary or emergency heat more often than necessary.
Learn the difference between your thermostat’s heat, auxiliary heat, and emergency heat settings. Some systems label emergency heat as “E-Heat” or use a separate switch. Understanding your specific controls helps you avoid costly mistakes.
Consider upgrading to a smart thermostat that monitors your system’s efficiency and alerts you when something operates abnormally. Many models will notify you if emergency heat runs longer than expected or if energy usage spikes unexpectedly.
Signs Your Heat Pump Needs Repair
If you find yourself relying on emergency heat frequently, your heat pump likely needs professional attention. Ignoring the underlying problem only leads to higher bills and potentially more expensive repairs later.
Watch for these warning signs:
- Emergency heat activating multiple times per week
- Outdoor unit covered in ice even when temperatures are above freezing
- Strange odors coming from vents when the heat runs
- Weak airflow throughout your home
- Rooms heating unevenly despite proper thermostat settings
- The system cycling on and off more frequently than normal
Addressing these issues promptly prevents minor problems from becoming major failures. A small refrigerant leak costs much less to fix than a burned-out compressor that results from running low on refrigerant for months.
Making Smart Decisions About Your Heating System
Understanding emergency heat empowers you to use your system correctly and recognize when something needs attention. You don’t need technical expertise to notice unusual patterns or ask informed questions when speaking with HVAC professionals.
Keep a simple log of when emergency heat activates, outdoor temperatures, and any unusual system behavior. This information helps technicians diagnose problems more quickly and accurately.
Check your thermostat setting today to confirm you’re using normal heat mode, not emergency heat. If you notice emergency heat running or your energy bills seem unusually high, contact a qualified HVAC technician to inspect your system before winter weather makes the problem worse and more expensive to resolve.
Taking control of how you heat your home reflects the same practical self-awareness that improves other areas of your life. Continue building that awareness by exploring more helpful articles about personal growth and healthy relationships on our site.