If you’ve ever noticed “EM heat” flashing on your thermostat and wondered what it means, you’re not alone. At Summers Comfort Heating & Air, we get this question all the time—especially during winter. The short answer is that EM heat, or emergency heat, is a backup heating mode your system uses when your heat pump can’t keep up or stops working properly. But there’s a bit more to it than that, and understanding how emergency heat works can help you avoid high energy bills and unnecessary wear on your system.
What Does EM Heat Actually Mean?
EM heat stands for emergency heat, and it’s built into heat pump systems as a secondary heat source. Normally, your heat pump transfers heat from the outside air into your home. But when outdoor temperatures drop too low, or if the outdoor unit fails, your thermostat can activate emergency heat to keep your home warm.
In most systems, EM heat comes from electric resistance heating strips or a gas furnace backup. Think of it as your system’s “Plan B” for when the main heat pump can’t do the job. It’s reliable—but it’s also energy-hungry, which is why it shouldn’t be your everyday heating mode.
When Should You Use EM Heat?
You should only manually turn on EM heat if your heat pump stops working or is covered in ice, or if a technician advises you to. In normal operation, your system automatically switches to backup heat as needed—so you don’t have to lift a finger.
If your home isn’t heating and the outdoor unit is visibly frozen or silent, emergency heat can buy you time until help arrives. But leaving it on too long can drive your energy bill sky-high. According to the U.S. Department of Energy, electric resistance heat can use up to three times more energy than a functioning heat pump.
Signs That EM Heat Is Running
Wondering how to tell if emergency heat is on? Look for these signs:
Your thermostat shows “EM heat” or “Emergency Heat.”
The outdoor unit isn’t running but the indoor air handler is.
You notice higher energy bills or a sudden spike in electricity use.
The air feels slightly different—hotter, but less efficient.
If these sound familiar, your system might be relying too heavily on backup heat. That’s when it’s time to schedule a check-up with a professional from Summers Comfort Heating & Air.
Why Emergency Heat Costs More
Here’s the catch: EM heat doesn’t transfer heat—it creates it. And creating heat from electricity is costly. In regions with mild winters, this mode might only run occasionally. But in colder areas, running emergency heat all season can lead to sticker shock.
That’s why our technicians often recommend regular heat pump maintenance to prevent situations that trigger EM heat in the first place. Cleaning coils, checking refrigerant levels, and testing sensors can make a world of difference in efficiency.
Can EM Heat Turn On Automatically?
Yes—and that’s a good thing. EM heat automatically activates when your system detects a problem with the heat pump or extreme outdoor temperatures. It’s a built-in safeguard designed to keep your home comfortable even during equipment failure.
However, if emergency heat stays on constantly, it usually means there’s an issue. It could be a stuck relay, a failing outdoor unit, or a thermostat misconfiguration. The team at Summers Comfort Heating & Air can quickly diagnose what’s happening and restore your system to its normal cycle.
How to Prevent Overuse of EM Heat
If you want to avoid running EM heat unnecessarily, these tips can help:
Maintain your heat pump at least once a year.
Keep filters clean to improve airflow and efficiency.
Don’t block vents with furniture or rugs.
Set reasonable temperatures—avoid extreme thermostat jumps.
Schedule regular inspections with trusted HVAC professionals like Summers Comfort Heating & Air.
Simple habits can save energy and prevent your system from switching to emergency heat too often. For additional home heating efficiency advice, check out ENERGY STAR’s Heat & Cool Efficiently guide — it’s full of practical tips on filters, thermostats, and system maintenance.
What to Do if EM Heat Stays On
If you’ve switched EM heat on manually, try turning it off after a few hours. If the home cools down quickly or the outdoor unit won’t restart, call for professional help. The issue might be as small as a tripped breaker or as serious as a failed compressor.
When customers call us at Summers Comfort Heating & Air about persistent emergency heat, we start with a full diagnostic check. We look for ice buildup, electrical issues, or faulty sensors that could trigger backup heat unnecessarily. Once we find the cause, we make sure your system runs efficiently again—without relying on costly emergency heat.
When to Call Summers Comfort Heating & Air
While EM heat keeps you warm in an emergency, it’s not meant for long-term use. If you’re unsure why it turned on—or if your system won’t switch back—contact Summers Comfort Heating & Air. We’ll inspect your heat pump, verify your thermostat settings, and ensure your home stays warm efficiently.
We help homeowners across Gastonia and the surrounding areas maintain reliable comfort year-round. Call Summers Comfort Heating & Air today at (704) 879-3644 or schedule a service online. Your comfort is always our priority—especially when EM heat decides to take over.
