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Does Emergency Heat Work In The Absence Of Power?

Does Emergency Heat Work In The Absence Of Power?

A dependable heat source is a necessity in most homes, particularly in colder climates. Assume your central heating system goes out due to a power outage at some point. This may cause you to wonder whether you can use your emergency heat without power.

A power source is required for emergency heat to function. This could be electricity, gas, oil, or hot water, depending on your backup system. In most cases, it is powered by electricity. When you set your thermostat to emergency heat, your system can use the electric heat strip directly.

Heat systems are made up of various parts and units. Continue reading to learn how emergency heat works, as well as alternative power sources for your home.

Emergency Heat And Unit Types

Does Emergency Heat Work In The Absence Of Power?

A typical heating system includes primary and secondary units. The main heat pump (usually located outside the building) is the primary unit, while the secondary unit is the emergency heat or EM heat, also known as the supplemental or backup unit.

EM heat is controlled by a manual button that activates a separate heating system from the outside heat pump. It could run on electricity, oil, or gas. It is used in an emergency when your heat pump is unable to function due to extreme cold or a breakdown.

Aside from the main heat pump outside your building, your thermostat has two additional heat provisions: the auxiliary and emergency heating systems.

When Should You Use Emergency Heat?

As previously stated, the primary unit shuts down immediately when the temperature falls two to three degrees below the thermostat’s set point or when there is a power outage. Typically, before switching to EM heat, an auxiliary unit works alongside your heat pump, providing extra support and allowing it to defrost.

You will have to manually turn on the emergency heat on your thermostat. This means you should check your thermostat to see if the emergency light is on, or you should inspect your heat pump outside for any problems.

Remember, this is an emergency heat, so use it accordingly. It should not be used as a primary heat source unless you want to pay exorbitant power bills (especially when it runs on electricity). Furthermore, emergency heat is not designed to last long.

If your heat pump is frozen and refuses to defrost despite the fact that your heater is turned on, look for physical damage outside. In windy areas, for example, a tree branch could fall on your heat pump. In this case, you must perform routine maintenance or repair while also switching to EM heat.

How Does An Emergency Heat System Work?

Most heat pumps have an emergency heat switch that is activated in an emergency. Depending on its power source, EM heat follows a separate heating system or channel from the heat pumps.

Switching it on disables the heat pump, even if it defrosts in the event that it stops working due to freezing. It must be manually turned off before the heat pump can function.

Thermostat Display Icons

Does Emergency Heat Work In The Absence Of Power?

Manual switching is usually done after checking your thermostat indicator. The thermostat display is made up of three icons. The “HEAT” icon represents the main unit or heat pump, whereas the “AUX” icon represents auxiliary or supplemental heat.

Based on your thermostat calculation or programming, this supplemental heat works automatically with the main unit. The thermostat detects when the main unit requires assistance and automatically activates the backup unit. Because this process is automatic, you are unlikely to notice.

The third icon on your thermostat is the “EM” icon, which indicates that it is time to turn on the emergency heat. When your heat pump and compressor can no longer compress air to produce heat, this icon appears.

The EM light illuminates and appears on the thermostat, indicating that it is time to turn it on. When you switch to EM heat, your main heater and compressor turn off automatically, allowing you to perform necessary repairs while the EM heat keeps the house warm.

Is It Possible To Have Emergency Heat Without Power?

Every heating process involves the conversion of energy from one form to another. The amount of energy required for this conversion is determined by the amount of energy produced.

A heat pump converts and compresses hot air before introducing it into the system (just the opposite of air conditioners). The EM heat is affected by power. Its power source ranges from (mostly) electricity to hot water.

What Is The Distinction Between Emergency And Auxiliary Heating?

Does Emergency Heat Work In The Absence Of Power?

The auxiliary heating system works in tandem with the main heat pump. In general, as the weather cools and the temperature drops, the heat pump becomes weaker and less effective.

When your system reverses to defrost the coils, the radiation strips automatically turn on to keep you warm.

The thermostat is set to turn on the supplemental heating as soon as the outside temperature falls below the threshold, which is usually two to three degrees below the threshold. The process and calculations are automated based on the thermostat settings.

Important Distinctions

The key distinction between auxiliary and EM heat is the automatic process. Most people are unaware of the auxiliary heating activities that take place behind the scenes between the thermostat and the heat pump. This is due to the fact that the process is automated, as opposed to the EM system, which must be turned on manually.

Another notable distinction is that the EM system consumes significantly more energy than the supplementary system. In fact, the auxiliary system communicates directly with the heat pump, so it lacks its own independent power source and has little impact on your bill.

How Long Can You Survive On Only Emergency Heat?

You should only use the emergency heating system in an emergency. This means that the EM system should be used for as long as the main heat pump system is being repaired.

If the heat pump freezes, the duration of your EM heat usage will be the time it takes to defrost if the heat pump is still operational. It is not cost effective to run the EM heat for an extended period of time, but that does not mean it cannot be run continuously. It would only have economic ramifications.

Aside from the high electricity bills, EM heat is also difficult on your plumbing system because it bypasses the traditional route for the main heat pump to provide heating.

Alternative Heat Sources In The Event Of A Power Outage

Aside from emergency heat, the following are some more cost-effective alternative power sources to consider.

  • Indoor kerosene heater: this is your go-to option when you want to cut your bills; it is very economical, but you must follow all safety precautions, especially in a ventless setting.
  • Propane heaters are very effective and efficient because they use liquid propane as fuel to heat medium to large spaces. Newer models are more efficient than 90% of the time. It comes in a variety of sizes.
  • Pellet stove: This type of stove is powered by recycled sawdust or wood shavings. It is available in a variety of sizes, allowing you to select the one that is best for your home.
  • Catalytic heater: it produces heat without using a flame, making it ideal for indoor use.
  • Solar heating is based on thermal mass and a large window facing south. These two are used to capture solar energy, which is then used to keep the house warm when the sun goes down.
  • Camping cooking bag: camp bags can be used to heat water for tea and cook pasta. It is an excellent choice for keeping warm.
  • Home insulation: Consider insulating key areas of your home. It slows the rate at which cold air enters your home.
  • The alcohol heater is powered by denatured alcohol. It burns cleanly and can be used indoors.
  • DIY Heater: This is only useful when all other heating options have been exhausted. You can make your own heater at home using common household items such as candles and ceramic bowls.
  • Wood Stoves: This is for those who have access to plenty of firewood, but it is very efficient and cost-effective. It is best installed near a window, and a chimney pipe can be used to direct the smoke out.


EM heat is powered by electricity. Your power selection should not be limited to cost alone; you should also consider efficiency and safety. You can also experiment with other alternative heat sources, but be cautious of potentially hazardous options, especially if you have children at home.

Does Emergency Heat Work In The Absence Of Power?

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Written by HVAC Contributor

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