How Do I Know When to Use My Heat Pump’s Auxiliary Heat?

For homeowners here in Anderson Township, Ohio, heat pumps are highly efficient, but they can be confusing as well. In order to take advantage of their efficiency, you need to be sure they’re operating the way they’re intended to operate. 

Whether you’re considering heat pump installation or are already using one of these heating and cooling systems, this means knowing when and how to use the auxiliary heat setting properly. Adams Heating & Cooling explains the best strategy for utilizing your heat pump’s auxiliary heat to keep your home comfortable and avoid wasting money this winter.

Refresher––How a Heat Pump Works

It’s important to first understand how a heat pump works before getting into the specifics of auxiliary heat. A heat pump is different from a furnace—electric heat pumps transfer heat from one area to another instead of creating its own heat. 

Air source heat pumps actually operate like an air conditioner when it comes to how they cool, but in the winter, they operate in reverse to heat your home. The heat pump system draws heat in from the cold air outdoors (yes, even though it’s cold, there’s still heat available!) and moves it indoors. Ground source heat pumps—also called geothermal heat pumps—use the same process but transfer heat between the ground and the air inside your home.

How Does Auxiliary Heat Work?

It just makes sense that an air source heat pump can struggle to draw warm air in cold temperatures less than 35ºF (or 40ºF, depending on who you talk to), so they need assistance in creating the desired indoor temperatures. That’s where your heat pump’s auxiliary heating system enters the picture. 

Auxiliary heat is a secondary heating source that supplements your central heating system when it struggles to meet your home’s heating needs. It’s typically powered by electric resistance heating, which involves an auxiliary heat strip similar to those in a toaster. Some heat pump systems may use gas or oil furnaces as auxiliary heating systems—these heat pump/furnace combos are known as dual-fuel systems

Auxiliary heat automatically activates when your heat pump faces:

Extreme Cold Weather

Heat pumps are highly efficient but become less effective as outdoor temperatures approach freezing. When it’s too cold for the heat pump to extract heat from the air, auxiliary heat provides the additional warmth needed to maintain comfort.

Rapid Temperature Changes

If you drastically increase your thermostat setting, the heat pump may struggle to heat your home quickly enough, triggering auxiliary heat. While this is helpful, it’s more energy-efficient to make gradual adjustments to avoid over-reliance on aux heat.

Defrost Mode Activation

During freezing conditions, frost can accumulate on the outdoor coil, reducing the heat pump’s efficiency. To resolve this, the system enters defrost mode, temporarily switching to auxiliary heat to keep your home warm while the outdoor unit defrosts.

Your auxiliary heat supplements your heat pump’s heat––it doesn’t replace it. They will work in tandem when the temperatures drop to those cold numbers. While auxiliary heat ensures your home stays warm during extreme conditions, it comes with higher energy consumption and costs.

The Difference Between Auxiliary Heat and Emergency Heat

Your auxiliary heat, as just described, supplements your heat pump’s heat when it needs it. On the other hand, your emergency heat takes over, or replaces, your heat pump’s heat.

Auxiliary Heat

Your auxiliary heat will kick in on its own when it’s needed by your heat pump (provided your heat pump’s in good working order, which can be ensured by annual checkups and maintenance).

You don’t have to give it a thought or switch anything over on your thermostat. Just leave your thermostat’s setting on Heat, and let it do its thing. You may have an aux heat indicator on your thermostat, which tells you when it’s on.

Emergency Heat

Your emergency heat is meant to be a true backup for your heat pump if there’s an emergency and the heat pump system stops working. Emergency heat completely takes over heating your home for your heat pump, shutting down your heat pump. 

Unlike auxiliary heat, this is completely within your control. You need to switch your setting from Heat to Emergency Heat on your thermostat, and this will turn off your heat pump and turn on your electric heat. This is where your energy efficiency disappears and your high energy bills appear.

Do not switch to your emergency heat setting unless your heat pump no longer works. Do not switch to emergency heat when the outdoor temperatures dip below 35ºF––your auxiliary heat will automatically step up to supplement your heat pump. 

If you do find yourself in the position of needing to use your emergency heat, turn it on, but then call one of our Adams Heating & Cooling technicians to come out to service your heat pump. If done relatively quickly, you may not even notice the issue reflected in your energy bill.

Contact Us for Heat Pump Services

Because auxiliary heat is automatic, you don’t really need to know when to use it—but you do need to know when to use emergency heat. Of course, if your heat pump isn’t performing as described or if it needs servicing, you should call one of our professionals at Adams Heating & Cooling to assess the situation and correct it. Give us a call, or you can request service online today.