Does Your Heat Pump Have Auxiliary Heating?

two heat pumps buried in snow

A heat pump provides comfort in an unexpected way: by extracting heat from the cold air outside. But what happens when temperatures are so low that there isn’t enough heat energy to draw from? The answer depends on the type of heat pump you have.

How Does a Heat Pump Work?

Unlike a gas furnace, a heat pump doesn’t generate heat. Instead, it transfers heat from one place to another. In heating mode, the outdoor unit absorbs heat energy from the air through a cool liquid refrigerant. The liquid is colder than the air, creating a temperature differential. This relative warmth gets compressed into a hot gas. The indoor unit blows air across the hot coils, distributing heat through the ductwork. As the gas cools, it turns back into the liquid refrigerant. And the process repeats.

Does a Heat Pump Stop Working In Extremely Low Temperatures?

At maximum capacity, a heat pump can create a 30-degree difference between the inside and outside temperature. That means if it’s 38 degrees outside, your home’s interior will be a cozy 68 degrees. However, as outside temperatures drop below 35 degrees, your heat pump's efficiency drops with it. At a certain point, the heat pump will switch to auxiliary heating.

Heat Pump Auxiliary Heat

In auxiliary heat mode, your heat pump generates warmth through electric resistance heating coils, similar to baseboard heating. A heat pump with this feature will turn on the supplemental heating if there isn’t enough heat energy outside to reach your desired temperature. (If your heat pump falls back on auxiliary heating frequently, brace yourself for a higher energy bill. Electric resistance heating isn’t nearly as efficient.)

Related: Should You Get a Furnace or a Heat Pump?

How Can You Tell If Your Heat Pump Has Auxiliary Heat?

Because temperatures in our region do occasionally dip below 30 degrees, it’s likely that your heat pump already has a backup heat source. Here’s how you can tell:

  • It says so on your thermostat: The next time temperatures plummet, take a look at your thermostat. If the display says “AUX,” this means your heat pump is in auxiliary mode.
  • Take a look at the equipment: If you see a series of electric heat strips within the indoor air handler, that’s the backup heating element.

What If Your Heat Pump Doesn’t Have Auxiliary Heat?

If you have checked the above and it appears that a heat pump is your sole heating source, you have a couple of options:

  • Have an HVAC technician inspect the unit to see if it allows for “add on” auxiliary heat. If it does, this is probably your most cost-effective option.
  • Consider installing a furnace. A high-efficiency gas furnace will get you comfortably through the coldest days when your heat pump can’t keep up with demand.

Turn to the Fairfax Area Heating Professionals

Heat pumps are tremendously efficient and provide reliable comfort all year-round. However, your particular heat pump model may need an additional heat source during extreme winter conditions. The experts at Air Treatment Company are happy to inspect your heating system and walk you through your options. To schedule your appointment, call (703) 270-0881.

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