For many people, fall is a magical time of year. Leaves begin to change, nights become crisp and celebrations like Halloween abound. But as the days continue to shorten and the temperatures slide toward winter lows, many homeowners consider the maintenance they’ll need for their HVAC systems. As you’re getting your heat pump inspected and cleaned, it’s also a good time to learn about auxiliary heat vs. emergency heat and how you can choose the right settings come winter.
Is Auxiliary Heat the Same as Emergency Heat?
Auxiliary heat vs. emergency heat may sound similar because both refer to the same backup heating component in your home. However, they have different functions and come on for different reasons.
What Is Auxiliary Heat?
Auxiliary heat is a system function that activates a backup heating source when your heat pump can’t meet your home’s heating needs on its own. Usually, auxiliary heat comes on automatically as needed depending on the outdoor temperature and how hard your heat pump has to work to keep up with your desired temperature setting. Many thermostats show or flash an AUX indicator when this setting is on.
Some homes have electric heating systems alongside older radiator heating or other comfort options. Secondary systems that aren’t connected to the main heat pump, like a fireplace, can serve as backup heating. However, they’re not automatic auxiliary heat.
How Does Auxiliary Heat Work?
Auxiliary heat relies on a secondary heat source. Electric resistance heat strips are common, though some systems also have a backup gas or oil furnace. When auxiliary heat is triggered, the secondary heat source comes on to help warm the house.
Potential triggers for auxiliary heat systems include:
- Very low outdoor temperatures
- A system going into defrost mode
- Raising the thermostat setting by several degrees at once
If auxiliary heat comes on, it powers down automatically when your home reaches the desired temperature and your heat pump can take over on its own again.
Is It Okay for Auxiliary Heat to Run?
Yes, the AUX function is designed to help ensure your HVAC system can keep you comfortable even when winter months get frigid. However, if auxiliary heat runs constantly or you think it’s running when it’s not that cold outside, it may indicate an issue with your heat pump. Consider getting a heating technician to inspect your HVAC system to determine why the auxiliary heat is running so often.
Does Auxiliary Heat Cost More?
Yes, auxiliary heat can cost more to run than relying on your heat pump alone. That’s especially true with electric resistance backup; for gas or oil systems, operating costs depend on fuel prices. Heat pumps are also fairly efficient because they move heat instead of making it. In contrast, electric resistance creates heat directly, which uses more electricity.
What Is Emergency Heat?
Emergency heat refers to a manual override setting built into heat pump systems. You have to manually turn on emergency heat, and when the setting is on, your thermostat may show EM HEAT or E. Sometimes, this indicator flashes on the screen of your thermostat.
How Does Emergency Heat Work?
When you select the emergency heat setting on your thermostat, the system shuts down your outdoor compressor completely. At that point, the only thing heating your home is the backup source. This differs from auxiliary heat, which automatically activates backup heating when needed to reach or maintain your thermostat’s set temperature.
Is It Okay for Emergency Heat to Run?
Like auxiliary heat, emergency heat is a part of your system design. However, you must turn it on manually, and you should only do that if there’s a specific reason your outdoor heat pump shouldn’t or can’t run. For example, you might turn on emergency heat if your outdoor unit freezes completely during a winter storm or breaks down.
Emergency heat is meant to be used as a temporary measure to keep your home at a safe temperature until you can get someone to address necessary heat pump repairs or the outdoor unit can run again.
Does Emergency Heat Cost More?
Yes, emergency heat can cost substantially more than relying on your heat pump, especially when it uses electric resistance heat. Commonly, emergency heat is generated by electric resistance heat strips, which are a little like the bars you see heat up inside a toaster. Creating heat with that kind of mechanism is less efficient than using a heat pump, and running emergency heat for an extended period can increase your electric bill.
How to Learn More About Auxiliary Heat vs. Emergency Heat for Your System
If you’ve never considered auxiliary heat vs. emergency heat before, break out your heat pump’s manual this fall so you can be prepared to make the right choices during cold snaps. Or, if you’re getting a new system installed, ask your heat pump installer to explain the settings.
