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

For homeowners here in the Cincinnati, Ohio, area, 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 when to use 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.

What Is Auxiliary Heat?

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 enough heat to maintain the desired indoor temperatures. That’s when the system switches on the heat pump’s auxiliary heat in Cincinnati.

The auxiliary system 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 and gas furnace combos are known as dual-fuel systems.

Your auxiliary heat doesn’t replace the heat pump’s heat. They will work in tandem when the temperatures drop to those cold numbers. If you notice your thermostat shows aux heat use often, even when outdoor temperatures are mild, it may be time to schedule a Cincinnati heat pump installation evaluation or a maintenance check to make sure everything is working efficiently.

Auxiliary Heat vs. 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, because you’re using more energy to heat your home.

Do not switch to heat pump emergency heat use unless your heat pump no longer works. Typically, this is only when you are waiting for heat pump repairs to be made. 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.

Why Auxiliary Heat Usage Increases in Winter

As winter temperatures in Cincinnati dip below freezing, it’s common to see your auxiliary heat turn on more often. This isn’t a sign that something’s wrong with your system: it’s actually your heat pump doing its job to keep your home warm and comfortable.

Unlike summer cooling, winter heating can push your system to work harder, especially during extreme cold snaps. Here’s why auxiliary heat usage increases in winter:

1. Colder Outdoor Temperatures Reduce Heat Pump Efficiency: A heat pump transfers warmth from outside air into your home. When outdoor temperatures fall below 35°F, there’s simply less heat to extract. To make up the difference, the system automatically engages the auxiliary heat source to maintain your set temperature.
2. Faster Temperature Recovery Is Needed: If you lower your thermostat at night and then raise it in the morning, the system has to work harder to quickly warm the house. This rapid recovery often triggers heat pump auxiliary heat to supplement the main system.
3. Defrost Cycles Trigger Backup Heat: During extremely cold weather, your outdoor unit can accumulate frost. When the system goes into defrost mode to melt the ice, the indoor unit pulls heat from the air to send to the outdoor unit. The auxiliary heat kicks on temporarily to keep warm air blowing inside.
4. Extended Heating Demands Mean Longer Runtime:  Cincinnati winters can stay cold for days or weeks at a time. Continuous low temperatures force the system to rely on auxiliary heat more often, which can increase energy use and auxiliary heat cost if not managed properly.

Auxiliary heat helps your home stay warm during extreme cold, but it isn’t nearly as energy efficient as your primary heat pump. Electric resistance heating uses much more electricity than a heat pump to produce the same amount of warmth. This higher energy demand can lead to noticeably higher utility bills if auxiliary heat runs for long periods.

How to Avoid High Energy Bills With Auxiliary Heat

While auxiliary heat is a helpful backup during Cincinnati’s coldest days, relying on it too often can drive up your monthly utility costs. The key to keeping your home comfortable without overspending is reducing how frequently your system needs to switch to this less efficient heating source. Here are a few smart strategies to help you save energy and money:

Maintain a Consistent Thermostat Setting

Large temperature swings can cause your system to work harder and trigger auxiliary heat. Instead of drastically lowering your thermostat at night and cranking it up in the morning, aim for a steady, comfortable temperature. A programmable or smart thermostat can make this easier and help you avoid unnecessary use of your heat pump’s auxiliary heat in Cincinnati.

Seal Drafts and Improve Insulation

Cold air sneaking in through windows, doors, or poorly insulated areas makes your heat pump work overtime. Sealing gaps, adding weatherstripping, and improving insulation will reduce heat loss and help your system maintain your desired temperature without relying on auxiliary heat.

Schedule Regular Maintenance

A well-maintained heat pump runs more efficiently. After your heat pump maintenance tune ups, components are clean, airflow is balanced, and your system isn’t overworking, which can minimize the need for auxiliary heat and help lower auxiliary heat cost.

Use Emergency Heat Only When Necessary

Remember: auxiliary heat vs emergency heat is not the same thing. Emergency heat should only be turned on manually if your primary system isn’t working. Relying on it unnecessarily can significantly increase your energy bills.

Schedule Heat Pump Repair at the First Sign of Trouble

If your system struggles to maintain temperature or auxiliary heat kicks on more than usual, it could be a sign of an underlying issue. With prompt heat pump repair from our HVAC professionals, your system operates at peak efficiency and prevents costly overuse of auxiliary heat. Catching heat pump repair problems early can save you from high energy bills and expensive emergency fixes later on.

Upgrade an Inefficient System

If your heat pump is old or struggling to keep up, it may be time to consider a replacement. A modern, energy-efficient system installed by Adams Heating & Cooling, a trusted Cincinnati heat pump installation company, can reduce how often auxiliary heat is needed and lower your long-term heating costs.

Frequently Asked Questions About Auxiliary Heat

What is auxiliary heat on a heat pump?

Auxiliary heat is a built-in backup heating function on your heat pump that turns on automatically when outdoor temperatures drop too low for your system to keep up on its own. It uses electric resistance heating to give your home an extra boost of warmth. In cold climates like Cincinnati, heat pump auxiliary heat is a normal part of winter heating and helps maintain a comfortable indoor temperature.

When should auxiliary heat turn on in winter?

Auxiliary heat typically kicks in when outdoor temperatures drop below 35°F or when your home’s thermostat calls for a big temperature increase quickly. For example, if you turn the thermostat up several degrees at once or your heat pump enters defrost mode, the auxiliary heat will automatically assist so your home stays warm even when the primary system is working at its limit.

What’s the difference between auxiliary heat and emergency heat?

The key difference is how and when they’re activated. Auxiliary heat turns on automatically to support your heat pump during very cold weather. Emergency heat, on the other hand, is turned on manually when the heat pump isn’t working properly or can’t operate. While auxiliary heat works alongside your system, emergency heat bypasses the heat pump entirely—and because it uses more electricity, it can lead to higher energy bills if left on too long. This is an important distinction between auxiliary heat vs emergency heat.

Does using auxiliary heat increase my energy bill?

Yes. Auxiliary heat is less efficient than your primary heat pump because it generates heat with electric resistance coils instead of transferring it from outdoors. This process requires much more energy, which can cause your auxiliary heat cost to rise quickly during extended cold periods. Occasional auxiliary heat use is expected, but frequent or constant operation can significantly impact your utility bills.

How can I reduce auxiliary heat usage to save money?

You can lower your reliance on auxiliary heat by keeping your thermostat at a steady temperature, sealing drafts around your home, and scheduling regular maintenance. Prompt heat pump repair can also prevent your system from overworking, while upgrading to a more efficient unit through Cincinnati heat pump installation may reduce auxiliary heat use in the long run. Avoid using emergency heat unless absolutely necessary, since it consumes even more energy.

Why is my heat pump always running on auxiliary heat?

If your heat pump seems stuck on auxiliary heat, it could mean the outdoor temperature is extremely low, your system is undersized, or there’s a mechanical issue. Dirty coils, low refrigerant, or poor airflow can all cause your heat pump to rely too heavily on backup heat. In these cases, scheduling a professional inspection or repair is the best way to restore efficiency and keep your energy costs manageable.

Can a smart thermostat help control auxiliary heat better?

Absolutely. A smart thermostat can prevent unnecessary auxiliary heat use by learning your heating habits and adjusting settings gradually. Instead of triggering a big temperature jump that turns on backup heat, it can make small, efficient adjustments throughout the day. Many smart thermostats can also send alerts if your system runs on auxiliary heat too often, helping you spot problems early and save money.

Contact Us for Heat Pump Services

Because it’s automatic, you don’t really need to know when to use auxiliary heat—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.