EM HEAT: WHAT IT IS AND WHEN TO USE IT

All regular thermostats have a special setting labeled “EM heat”? Many people falsely assuming it’s a setting for you to switch on during freezing temperatures. However, this isn’t true. “EM” stands for emergency, and this secondary heating system is a back-up to keep your house warm when your primary heat fails. So, you don’t want to go switching it on without knowing what you’re doing. 

What is EM Heat? 

Most systems have a heat pump as its primary setting and activate their secondary (gas, oil, or electric) heating when supplemental, or second-stage, heating is required. In colder climate, all heat pumps need a secondary heating source because your heater taps into this setting when outside temperatures drop too low.

However, if you turn on your EM heat manually, you begin drawing heat only from the secondary source. Now, instead of working with your main heat pump, your backup is working solo. This is way less efficient than your primary heating system, so you should only use it in real emergencies unless you want to pay exorbitant heating bills. 

How Does EM Heat Work? 

As we mentioned above, homes with heat pumps come with a two-part system: the heat pump and the auxiliary heating source. The primary heat pump is usually located outside of the house, while the second stage heating source is inside. 

The second heating stage is designed to be a supplemental source of heat when the temperature is too low for your heat pump to extract heat from the outside. Different systems and thermostats have different methods of determining when to activate this secondary source. Typically, this secondary heat source is automatically triggered when temperatures are below the set threshold. 

Additionally, the heat pump, which is outside on most houses, collects frost on the coils. When the heat pumps turn off temporarily to defrost the unit, this secondary source kicks in automatically. As a result, it is not necessary to switch to the EM heat setting yourself. Your thermostat will indicate when the setting is on, usually with a light. 

While this secondary system is automatic (and mostly used in accordance with your primary heating system), you can turn it on manually. This is when it's referred to as “EM heat.” When you turn on your EM heat, you’re telling your heating system to stop using your heat pump and only use this supplemental source.