Emergency Heat vs. Heat on the Thermostat: When You Should Use Each Setting

You might like the idea of using an energy-efficient heat pump to control your home’s interior atmosphere for both heating and cooling. However, if you live in an area with tough winter weather, you may worry that a heat pump won’t keep up with the cold, leaving you shivering. Combatting a nasty cold snap is why some heat pumps include emergency heat settings. 

Learn more about emergency heat versus heat settings, how they work, and how they differ from one another.

What Are the Differences Between Emergency Heat and Heat?

The main difference between emergency heat versus heat settings on a heat pump thermostat is that the heat setting is for normal heat pump operation, while the emergency heat mode (or EM mode) is meant for dangerously low temperatures. The EM mode activates a secondary heating system to deal with below-freezing temperatures during a winter cold snap. 

Understanding a Heat Pump’s Operating Modes

A heat pump is a device that provides both heating and cooling capabilities for a house. It typically runs from electricity and is more energy efficient than other heating and cooling systems made for homes.

When heating the home, the heat pump could offer up to three potential modes, depending on the system you’re using.

Normal Heating Mode

The heat mode is the normal, day-to-day operating mode. As long as outdoor temperatures are 40 degrees Fahrenheit or warmer, most heat pumps can operate sufficiently in the normal heat mode.

Emergency Heating Mode

Emergency heating mode is a secondary heating source, such as a gas furnace, that begins running when the heat pump’s normal heating mode is unable to keep up with the low outdoor temperatures. The emergency heat mode could work in conjunction with the normal heat mode. (Not all homes have secondary heat sources installed.)

The emergency heat source can operate alone if the heat pump breaks down or stops working completely due to extremely cold weather.

Auxiliary Heating Mode

Some heat pumps use the term auxiliary heating to signify when the secondary heat source is operating at the same time as the heat pump’s normal heat mode. Auxiliary mode would help heat pumps combat low temperatures. 

In systems that use an auxiliary mode, the emergency heat mode operates only if the heat pump is unable to work at all.

Emergency Heat vs. Heat on a Thermostat: Differences in Performance

Learn more about the emergency heat versus heat settings on your thermostat and how they differ in several categories.

System Design

How do I know if I have a heat pump with an emergency heat mode? If this option is available, your heat pump’s thermostat will have a mode listed as “EM,” “E,” or “Emergency Heat.” You’ll have a secondary heat source, such as a gas-powered furnace, that serves as the emergency heat option when the heat pump cannot deliver enough heat on its own.

If the thermostat only has heat mode available, you would not have a secondary heat source to supplement your heat pump.

If you believe you need a secondary heat source because your heat pump is having trouble keeping up with low outdoor temperatures, contact a local heat pump installation company for help.

Purpose

The regular heat mode for the heat pump should operate the majority of the time. It can deliver adequate heat for the home as long as temperatures are 40 degrees or higher. The effectiveness of the heat pump as a heater falls off during below-freezing and lower temperatures.

Emergency heat mode should only operate when the heat pump is not working or temperatures are too low for it to operate effectively.

Cost to Operate

Many people select regular heat mode with a heat pump because it costs less to operate than a traditional furnace. If you have to run emergency heat regularly, though, your heating bill will increase because the secondary heat source costs more to operate than the heat pump.

Fuel Sources

Although several types of heat pumps exist, most of them run on electricity. When running in regular heat mode, you’ll use electricity. 

If you need to run in emergency heat mode, you’ll use whatever kind of fuel is associated with your secondary heat source, whether it’s natural gas, propane, oil, or electricity.

When to Use Them

Regular heat mode with a heat pump efficiently heats a home until outdoor temperatures reach about 40 degrees. However, the heat pump becomes ineffective once outdoor temperatures are below freezing, which is why you need a secondary heating source. 

The device associated with emergency heat mode can operate effectively at any outdoor temperature.

Automatic vs. Manual Operation

When does a heat pump switch to emergency heat, and is it automatic? You can decide whether to have emergency heat mode start working automatically or whether you want to activate it manually. Some people prefer to activate emergency heat manually because of the extra cost associated with running it.

A system that activates emergency heat mode automatically measures the outdoor temperature to determine when to make the switch. This option functions smoothly, as emergency heat can kick on if temperatures drop while you’re sleeping.

Heating Alternatives

If you want to use a heat pump for regular heat mode, but you don’t want the expense of setting up a secondary heat source for emergency heat mode, you might consider a few heating alternatives, including:

• Wood-burning fireplace

• Gas fireplace

• Electric space heater

• Propane space heater

• Electric radiator

• Radiant floor heating

These heating products can be expensive to operate, so you should only use them sparingly. In other words, if your region’s outdoor temperatures rarely dip below 40 degrees, you could use one of these heaters as a supplemental option. You’d then let the heat pump handle the majority of the home’s heating needs.