When To Use Emergency Heat On a Heat Pump (These Rare Cases)

Josh Mitchell

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Josh Mitchell

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Holly Curell

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Heat pumps let you maintain a comfortable home environment, and most heat pumps have have an emergency heat setting that provides an intense burst of warmth when you need it most.

However, emergency heat can be inefficient and cause damage if it isn't used appropriately.

Many homeowners I've worked with struggle to use emergency heat correctly, but in this guide, I'll explain what it is, when you should be using it, and how you can maximize the benefits.

How Does EM Heat Work In Heat Pumps?

Emergency heat (EM) in a heat pump system is the backup heating method.

Typically, when a heat pump is in heating mode, it pulls in heat from the outside.

When the temperature drops the outdoor air is too cold to draw in heat, and the heat pump efficiency drops.

That's when emergency heat kicks in, allowing the heat pump to continue operating as it should. 

Heat pump EM usually comes from electric resistance heat strips - small heating coils located in the air handler of the indoor unit in the heat pump. 

Once activated, heat is generated and blown into the indoor space by the heat pump fan system, raising the indoor temperature. 

Electric heat strips are the most common emergency heat source, but some heat pump systems can use a gas or oil-filled component. I usually find these more complicated, but they can be practical if you don't have an outlet nearby. 

Not all heat pumps have emergency heat capability, but it's common for appliances in colder areas. Systems with EM heat usually have a red indicator light on the thermostat to signal when the emergency heat is activated, but it can vary by make and model.

EM heat is often activated automatically, so I recommend checking your specific heat pump specs to see if it has EM heat and how to tell when it's in use. 

Why You Should Use EM Heat Sparingly

EM Consumes A Lot More Energy And Costs More To Operate

Emergency heat will help you stay warm, but it uses far more energy than regular heat pump operation.

The EM heat source can use 2-5 times the amount of electricity, and once it kicks in, your bills can skyrocket.

The table below shows just how inefficient EM heat can be and how much more it could cost you if it relied on emergency heat for a week:


Normal Heat Pump
at 30°F for 1 week

Emergency Heat
at 10°F for 1 week

Watts per Hour

4,000 Watts

4,000 Watts + 15,000 watts for EM heat

House of Use (per day)


10 hours + 10 hours of EM heat

Total kWh (per week)

280 kWh

1330 kWh

Cost per kWh



Total Cost per Week



As you can see, staying warm in cold conditions using emergency heat could cost you an extra $160 a week, so I recommend using it sparingly.

When Do You Use Emergency Heat?

Emergency heat systems shouldn’t be used all the time, but they are useful in a few situations:

Your Heat Pump Is Damaged

Heat pumps typically have some external components to draw heat in. These can become damaged (usually by falling debris or branches) and can stop your heat pump from functioning. 

Temporary emergency heat provides an alternative heat source so your pump can continue maintaining the temperature in your home without interruption.

This allows you to stay warm while repair work is carried out. 

Your Heat Pump Is Frozen

Heat pumps often operate in cold temperatures, and the outdoor unit can freeze over (usually the outdoor coil responsible for extracting the heat from the air). A frozen coil will prevent the heat pump from working and can damage the appliance.

Emergency heat can thaw the frozen coil and get your heat pump working again, and modern heat pumps have an automatic defrost cycle that uses the EM heat. Temporary bursts of heat from the emergency heat source will protect the unit and keep it functioning in colder conditions.

Heat Pump Is Going Through Maintenance

Your heat pump will need some routine maintenance and should have a professional inspection at least once a year.

During scheduled maintenance or repairs, your heat pump won't be able to draw in heat as usual. However, short-term use of the emergency heat can keep your home comfortable until the HVAC technicians have completed their work.

Just remember to switch back to regular operation once the maintenance is done, or your electricity consumption will dramatically rise.

Weather Is Below Freezing

Your heating pump will work well when the temperature is about 30 to 35 degrees, but below that point, it may struggle.

In very cold conditions, your heat pump won’t be able to draw in warm air to meet the demands of your interior thermostat, and this is when you’ll need an alternative heat source for your home.

The emergency heating coil within the heat pump will kick on or can be manually activated to boost the temperature by a few degrees.

This won’t only heat your home; it will help defrost any parts of the pump which may have been frozen by the cold.

It isn’t only those in cold conditions who may need to use the emergency heat, as even those who live in mild conditions can have a few freezing nights a year.

For A Quick Warm Up

It isn't efficient, but your emergency heat will provide faster warmth than your standard heat pump operation.

If you are returning to a cold house or need some fast heat, you can use the EM supplemental heating to raise the temperature more quickly.

It's a helpful feature for homes with older/vulnerable people, but I recommend checking the temperature closely and switching back to regular heat pump operation as soon as possible.

The "Don'ts" Of Using Emergency Heat

Emergency heat can be a lifesaver (literally in some cases), but only if you use it appropriately. Here are my 5 tips to consider before you activate it:

  1. 1
    Don't Use It Just Because It's Cold Outside
    Emergency heat is, as the name suggests, only for emergencies. It can provide very effective heating, but you must be careful about how and when you use it because it could cost you 4 or 5 times as much. Only use it in extreme conditions. 
  2. 2
    Don't Use It For Longer Periods Of Time
    Continuous use of heat pump EM heat is inefficient and costly. If you really need it that often, you should look for alternative, more economical heat sources.
  3. 3
    Don't Neglect Regular Maintenance
    Automatic emergency heat can make you think everything is fine with your heat pump because it runs uninterrupted, but that's not always the case. Always check it monthly, and have a professional inspection once a year. 
  4. 4
    Don't Fix The Underlying Issues With Main Heat Yourself
    If you find an issue with the primary heat source, don't attempt to fix it yourself (unless you're a qualified technician). Improper repairs can exacerbate the problem, and I recommend calling a professional to help you. 
  5. 5
    Don't Ignore Insulation Issues
    Emergency heat often kicks in because your home isn't retaining heat properly. Investing in wall, floor, window, and door insulation can make a big difference and prevent your EM heat from kicking in unnecessarily.


Will Emergency Heat Defrost The Heat Pump?

Yes. Your emergency heat will trigger a defrost cycle and force heat to flow throughout the device. If your heat pump is not defrosting properly, then consult a professional for help.

Does The Heat Pump Automatically Switch Emergency Heat?

Yes, your heat pump should automatically switch to emergency heat when it’s 30 degrees or below. You can activate it manually if there’s an emergency.

What Is The Difference Between Auxiliary Heat And Emergency Heat?

Auxiliary and emergency heat are similar as heat is provided from a secondary source. However, auxiliary heat works with the heat pump's regular operation, while emergency heat operates independently during extreme conditions or malfunctions.

What Happens If You Accidentally Turned-On Emergency Heat?

Once you turn on emergency heat, your heat pump will start to provide more heating and consume more electricity, leading to higher bills. I recommend turning it off as soon as you notice to optimize the energy use.

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Josh Mitchell


Josh Mitchell
My name is Josh and I am obsessed with home appliances. From portable AC units to heaters and air purifiers, I enjoy testing, learning and using these devices to improve the air quality inside my family home.

My Favorite Home Appliance?

Midea U Shaped Window Air Conditioner

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