What Is EM Heat on My Thermostat? A Dallas Homeowner's Guide
You walk up to your thermostat on a cold Dallas morning and see something you've never noticed before — "EM Heat" or "Emer" glowing on the screen. Your first thought is that something is wrong. Your second is whether your electric bill is about to climb.
Most Dallas homeowners never see this indicator until a cold snap hits. When it appears, it raises real questions fast. What does it mean? Did you accidentally turn it on? Is your heat pump broken?
We'll walk through what EM Heat on your thermostat means, how the setting works, what it costs to run, and when it's time to call a technician. If your system is showing EM Heat right now and something feels off, our Dallas air conditioning repair team is available to take a look.
What Does EM Heat Mean on a Thermostat?
EM Heat stands for Emergency Heat. When this setting is active, your heat pump shuts off completely. Your system switches to a backup electric resistance heater instead. This backup source uses significantly more energy than your heat pump and is designed only for short-term use — typically when your outdoor heat pump unit has stopped working. If you did not manually switch on EM Heat and outdoor temperatures are mild, have the system checked by a licensed HVAC technician.
Different thermostat brands display this setting in different ways. They all mean the same thing.
Thermostat Brand | How It Displays |
Honeywell Home | Em Heat |
Nest | Emergency Heat |
Ecobee | Emergency Heat |
Carrier | EM Heat |
Trane | Emer Heat |
Lennox | EM Heat |
If you see any of these on your screen, your system is running on backup heat. The next step is understanding whether that's normal for the conditions — or a sign something needs attention.
How EM Heat Works Inside Your HVAC System
Your heat pump works by pulling heat from the outdoor air and moving it into your home. It does not generate heat the way a furnace does. This makes it efficient — but it has limits when temperatures drop hard.
When outdoor temps fall far enough, the heat pump struggles to pull enough warmth from the air. At that point, your system activates backup electric resistance strips inside the air handler. These strips generate heat directly, the same way a space heater does — just at a much larger scale.
That backup system is what runs when EM Heat is active. The outdoor heat pump unit is completely bypassed. Only the resistance strips are heating your home.
Electric resistance heat is reliable. It delivers warmth fast. But it uses two to three times more electricity than a functioning heat pump to produce the same result. That gap is why EM Heat is built for short-term use — not as a day-to-day heating source.
Our Dallas technicians regularly find systems that have been running on EM Heat for several days without the homeowner realizing it. By the time the utility bill arrives, the cost difference is easy to see.
EM Heat vs Auxiliary Heat — What Is the Difference?
These two settings cause more confusion than almost anything else on a thermostat. They are not the same thing, and the difference matters.
Auxiliary Heat turns on automatically when the heat pump needs help on a cold day. The heat pump is still running. The backup strips kick in alongside it to make up the difference. You may see "Aux Heat" on your screen during cold Dallas nights and that is completely normal.
EM Heat shuts the heat pump off entirely. The backup strips are doing all the work. The outdoor unit is not running at all. This is not a normal operating mode — it is a fallback for when the heat pump cannot function.
The simplest way to separate them:
- Aux Heat — assists the heat pump when temps drop
- EM Heat — replaces the heat pump when it stops working
One other thing to watch: if "Aux" appears on a mild day when temperatures are well above freezing, that can point to a system issue worth investigating. Low refrigerant or a struggling heat pump can trigger auxiliary heat at the wrong times.
When Should You Use the Emergency Heat Setting?
The short answer is: only when your heat pump has clearly stopped working.
EM Heat is not a way to heat your home faster. It is not a cold-weather boost. It is a temporary backup that keeps your home warm while the heat pump is out of service. Running it for any other reason means paying two to three times more for heat you could be getting from a functioning system.
Here is when switching on EM Heat manually makes sense:
- Your outdoor heat pump unit has stopped running completely
- The unit is frozen solid and not cycling through a defrost mode
- You hear unusual sounds from the outdoor unit that suggest mechanical failure
- A technician has confirmed the heat pump needs repair and told you to use the backup setting in the meantime
Here is when to call a technician instead of switching it on yourself:
- Your thermostat switched to EM Heat on its own during mild weather
- Outdoor temps have risen but EM Heat is still active
- You are not sure whether the heat pump is actually broken or just struggling
If your system activated EM Heat automatically during an extreme cold night in Dallas, that may be normal. Monitor it. If it stays on after temperatures rise or comes on when conditions do not call for it, that is the time to have it looked at.
What Does Running EM Heat Do to Your Electric Bill?
The impact shows up fast. A functioning heat pump delivers two to three units of heat for every one unit of electricity it consumes. Electric resistance strips deliver exactly one unit of heat per unit of electricity. That gap is not small — it shows up directly on your Oncor delivery charges and your retail electricity rate every month.
Running EM Heat for a single day during a cold stretch costs noticeably more than running your heat pump. Running it for several days without realizing it can add significantly to a winter utility bill in Dallas.
The fix is not to avoid EM Heat when you genuinely need it. The fix is to resolve the heat pump issue so you rarely need it at all.
A few things that affect how much EM Heat costs to run:
- The size of your home and your air handler's resistance strip capacity
- How long the system runs each cycle to reach your set temperature
- Your current retail electricity rate through your Dallas provider
- How many days the system stays in emergency mode before the heat pump is repaired
Our Dallas HVAC team can inspect your heat pump the same day and confirm whether EM Heat use is necessary or whether a repair will get your system back to running efficiently. The sooner the heat pump is back online, the sooner your bill returns to normal.
Dallas Heating Issues Don't Wait — Neither Should You
If your thermostat is showing EM Heat and your heat pump has not restarted, your system needs a professional inspection. Every day it runs on backup heat costs more than it should. Our licensed Dallas HVAC technicians can check your heat pump, identify what stopped it from running, and get it back online fast.
Berkeys Plumbing, A/C & Electrical has been serving Dallas homeowners with heating and cooling repairs since 1975. Our Dallas team brings 50 years of North Texas expertise to every service call — from a straightforward heat pump repair to a full system diagnosis.
We are available 24/7 to take your call. Same-day service is available throughout Dallas, Park Cities, East Dallas, Lakewood, and the White Rock Lake area.
Frequently Asked Questions
EM Heat stands for Emergency Heat. It is a backup heating mode that shuts off your heat pump and runs electric resistance strips instead. It is designed for short-term use only — typically when your outdoor heat pump unit has stopped working.
Yes, some systems will switch to Emergency Heat automatically during extreme cold. This is not always a sign of a problem. If EM Heat stays on after temperatures rise or activates during mild weather, have your system inspected by a technician.
Auxiliary Heat assists your heat pump when outdoor temps drop — the heat pump keeps running. EM Heat shuts the heat pump off completely and runs only the backup strips. Aux Heat is normal; EM Heat is a fallback for when the heat pump stops working.
Not always. Your system may switch to EM Heat during very cold weather as a protective measure. If EM Heat appears during mild temperatures or stays active after a cold snap passes, that is when a technician should take a look.
Most mini split systems include electric resistance heat strips that act as a backup heat source. This works similarly to emergency heat in a standard heat pump system. Check your unit's manual to confirm whether your model includes this feature.