Emergency Heat on Your Heat Pump: When to Use It and Why It's a Last Resort

Switching your heat pump to its "emergency heat" setting is a short-term solution for extreme cold or system failure, but it should be used sparingly due to energy costs that can be over six times higher than normal operation. Relying on this backup system can lead to significantly higher utility bills, making it crucial for homeowners to understand its proper role. This guide explains what emergency heat is, when it’s appropriate to use, and the financial implications of activating it.

What is Emergency Heat on a Heat Pump?

An Emergency Heat setting (often labeled "EM Heat" on your thermostat) is a backup heating system built into most heat pumps. It is designed to take over when the primary system cannot function effectively, typically due to freezing outdoor temperatures or a mechanical failure. The most common type of heat pump works by extracting heat from the outside air and transferring it indoors. However, when temperatures drop below a certain point, this process becomes inefficient.

"Emergency heat is like the spare tire of your heating system—it’s there when your main heat pump can’t do its job, whether due to extreme cold or a breakdown," says Danny Pen, president at New Era Plumbing and HVAC in Dracut, MA. "It’s a backup system that uses more energy, so think of it as a short-term fix rather than your go-to solution."

This backup system usually consists of electrical resistance heating strips, which generate heat directly but consume a large amount of electricity. Homes with traditional gas furnaces do not have this specific feature, as their primary systems are designed for harsh winter conditions.

When Should You Switch to Emergency Heat?

You should only manually activate emergency heat in two specific scenarios: when your heat pump is malfunctioning or during periods of severe cold that exceed your unit's operational capacity.

• Equipment Failure: If your heat pump is broken, iced over, or clearly needs repair, switching to emergency heat is a smart temporary measure to maintain warmth until a professional can service the unit.
• Extreme Cold Temperatures: Heat pumps have an efficient operating range. For older models, this is typically below 20–25°F. When the outdoor temperature drops below this threshold, the system struggles to extract heat, and emergency heat can provide necessary supplemental warmth. "However, some modern heat pumps can perform well even in very low temperatures," notes Pen.

It is not recommended to use emergency heat as a routine heating source. The system will automatically engage its auxiliary heat (which is part of the normal heating cycle) during moderate cold spells without needing manual intervention.

Why is Emergency Heat So Expensive to Run?

The primary drawback of emergency heat is its high operational cost. Unlike a heat pump, which moves heat efficiently, emergency heat generates heat directly through electrical resistance. This method is far less efficient, leading to a substantial increase in energy consumption.

According to data from Home Inspection Insider (2023), running emergency heat can cost over six times more per day than running a standard heat pump. This drastic difference can lead to unexpectedly high energy bills over just a few days of use.

"The pro is obvious—you won't freeze, but the downside will be really high energy bills," says Pen. The following table illustrates the potential cost difference based on average electricity rates:

*Estimates based on average household usage and national electricity rates. Actual costs will vary.

What Should You Do If Your Heat Pump Isn't Working?

If you suspect a problem with your heat pump, the safest and most effective course of action is to contact a licensed HVAC professional. Attempting a do-it-yourself repair is not advisable and can be hazardous.

"Fixing your heat pump yourself is like trying to repair an airplane mid-flight—it’s risky and can lead to dangerous outcomes like electrical fires, gas leaks, or system damage," warns Pen. "Attempting DIY fixes is not only a risk to your safety, but it also voids warranties, and often worsens the problem."

Based on our experience assessment, the key takeaways for homeowners are:

• Use emergency heat only as a temporary solution during a system breakdown or profound cold snap.
• Be prepared for a sharp increase in your electricity bill when the setting is active.
• Schedule regular maintenance for your heat pump to prevent issues, especially before the winter season.
• Always contact a qualified HVAC technician for repairs rather than attempting them yourself.