Have you seen AUX on your thermostat and want to know what it indicates? Often, AUX means auxiliary heat, a backup heat source that can provide some heat during extreme cold or to supplement the heat pump’s output if it’s unable to effectively heat your home. By learning what AUX means on a thermostat, you can use your HVAC system efficiently, lower your bills and know when to call us. What is heat meaning; when does aux heat turn on, and should we be concerned?
What Is AUX Heat on a Thermostat?
In response to a query about the thermostat’s AUX heat, this refers to supplementary heating capacity which is used in conjunction with your heat pump.
Heat pumps are designed to move heat from the outdoor air into your home effectively. When the outside air is exceedingly cold, however, heat pumps will no longer have an adequate capacity to generate sufficient heat.
At this time, your thermostat will turn on the auxiliary heat to maintain your pre-selected room temperature.
Auxiliary heat may consist of:
- Electric resistance elements
- Gas furnace (in dual-fuel systems)
- Oil furnace (uncommon)
The system turns on automatically, usually without your having to take any further action.
What Is Auxiliary Heat on a Thermostat?
This is also commonly asked among home owners. What is auxiliary heat on a thermostat and how is it different from main heating?
Auxiliary heat is an additional heating mode that turns on only when your main heat pump requires some additional help. Your auxiliary heat may kick on the following circumstances:
- Outside temperatures are quite cold
- Indoor temperatures fall below the thermostat’s set point in several degrees
- Heat pump goes into the defrost mode
- Heat pump fails to raise the inside temperature quickly enough
As soon as the house reaches its set temperature, the auxiliary heat is disabled.
AUX Heating Meaning
AUX heating meaning there is no need to explain AUX meaning, because when your backup heater turns to work it’s a backup heater, the backup system will help your heat pump system in heating your house as it needs the supplement.
Usually, the AUX heating system can be automatically activated by the heat pump thermostat if any following conditions are met:
- It was set as the heating season and the temperature reached its lowest setting.
- Your home reached its temperature of the setting thermostat temperature.
- In this case, your AC may just need some supplementary heat supply, which may be needed at the very low room temperature situation.
Generally it is normal to find AUX heating sometimes.
What Does AUX Heat Mean?
Is AUX heat an issue in my heating system? You’re likely asking if you’re reading “AUX heat” on your display, what it could mean and if there’s a reason to worry. The AUX heat setting signals to you that your heat pump has turned off temporarily in favor of your backup heating system for some reason.
Typically, this temporary change in the heating method is temporary and could be caused by;
- Temperatures dropping below zero Outdoor temps plunging
- The thermostat being reset to a significantly lower temp mode DEFROSTMODE
- The heat is turned off temporarily so the outer part of the system can defrost the ice on it
When Should AUX Heat Turn On?
Auxiliary Heat Explained
Here are some typical reasons Auxiliary Heat turns on.
When Outside Temps are Extremely Cold
When outdoor temperatures drop significantly, your heat pump becomes less able to regulate temperatures on its own. Additional heat is necessary until the heat pump is able to keep pace.
Big Temperature Shifts
Once your home heats up a number of degrees the system may switch on auxiliary heat. You’ll be able to bring your house to the ideal temperature without expending excessive energy by only turning up the thermostat by a single degrees.
The Defrost Cycle
Heat pumps use a defrost cycle in cold temperatures in order to get rid of ice and snow from the exterior unit’s fins. When this is happening your heat pump has turned to auxiliary heat to send you heated air while it melts the ice.
Is AUX Heat Expensive?
- Does AUX Heat Cost A Lot?
- The most significant point that the AUX heat does: typically more energy intensive than your heat pump. Electric resistance uses a LOT of electricity, so you likely do not want to run Your Aux Heat a lot – unless you don’t mind a lot of utility bills to increase your energy bills a lot.
The better approach toward more efficient operation:
- Don’t make extreme changes in the thermostat setting.
- Change Your Air Filter Regularly.
- HVAC check-ups are in order – schedule them regularly.
- Check the draft on windows and doors for leakage. Maintain current thermostat settings.
Is It Normal for AUX Heat to Stay On?
Should My AUX Heat Be On Constantly? Your AUX heat usually should only come on when it’s very cold and the air pump can’t meet the heating demands.
However, if your auxiliary heat has been running constantly, you may have one of the following issues:
- Your air filter is dirty
- Your home is too cold
- For your current refrigerant your heat pump itself is not working
- Properly heat pump fan control module,
- Your exterior heating coil is frozen
- Faulty thermostat your electric heat source isn’t getting power
If your auxiliary heat system stays on all the time or you have difficulty staying comfortable, have your system professionally inspected.
Emergency Heat vs AUX Heat
When Emergency Heat Is Used and Auxiliary Heats The AUX and emergency heat stages come at different times to add heat to the air
|
AUX Heat |
Emergency Heat |
| Turns on automatically |
Activated manually |
|
Assists the heat pump |
Completely bypasses the heat pump |
| Used during normal cold weather |
Used only if the heat pump fails |
|
More energy efficient than emergency mode |
Usually more expensive to operate |
Emergency Heat should only be used if your heat pump isn’t working properly.
Tips to Reduce AUX Heat Usage
In order to reduce energy costs, and auxiliary heat:
- Ensure HVAC filters are changed on a regular basis.
- Schedule a yearly maintenance for the heat pump.
- Do not try to countersink or “sag” your thermostat.
- Open the insulation in your home.
- Use weather stripping to seal any gaps about doors and windows.
- Keep outdoor air conditioning units clear of snow leaves and dirt.
With correct maintenance, it will be able to run efficiently through the winter.
When Should You Call an HVAC Professional?
You should contact an HVAC technician if:
- AUX heat remains on 24/7.
- Your room isn’t at the set temperature.
- Huge spike in your energy bills.
- The heat pump is noisy.
- The thermostat displays error messages.
- The machine is cyclic about modes between heating mode.
Prompt repairs avoid more expensive and serious HVAC problems.
Why Select 75 Degree AC?
When it comes to heater as well as air conditioning solutions, 75 Degree AC is your go-to group. For lots of years we have actually given service to your location and remain qualified in performing premier heat as well as ac system solutions, keeping the devices properly.
These are the kind of services we have offered so far:
- Heat pump repair service as well as support
- Thermostat installments and repair as well as help AC system reviews
- Heating system repair
- Urgent cooling and heating solutions
- Energy effectiveness system remodeling
Along with the years of proficiency, our trained experts will rapidly find your heater repair work concern as well as present you with best alternative.
Conclusion
Now you have insight to your auxiliary heat usage by asking, what does AUX mean on a thermostat. Knowing these specifics allows you to optimize the performance of your heater and helps you realize if you need HVAC maintenance assistance for your device. The aux heat meaning essentially involves a system that assists your primary unit.
If your heating has been asking you what is AUX heat on thermostat, auxiliary heat, or even asking, what do AUX heat mean, aux heat is a pretty regular aspect that keeps our homes nice & comfy.
If your AUX has taken over the house, or you are a poor heating performance for your family, give a 75DegreeAC call to set you up for a HVAC maintenance review.
FAQs
What does AUX mean on my thermostat?
AUX stands for auxiliary, and it’s nothing to worry about. When your thermostat shows “AUX” or “AUX Heat,” it just means your heat pump has switched on a backup heat source to help it keep up. Think of it as your system asking for a little extra muscle, not a warning that something’s broken.
Why did AUX suddenly show up on my screen?
Usually it’s the weather. Heat pumps pull warmth from the outside air, and when it gets cold enough outside, there’s simply less heat out there to grab. Your system leans on the auxiliary source to fill the gap and keep your home at the temperature you set. It can also pop up if you bumped the thermostat up several degrees at once, or during a brief defrost cycle on really cold mornings.
Is AUX heat the same as emergency heat?
No, and this trips a lot of people up. AUX heat kicks on automatically and works alongside your heat pump. Emergency heat (often shown as “EM Heat”) is a manual setting you’d only switch on if your heat pump itself has stopped working. If you’re not sure which one you’re seeing, check whether you turned it on yourself if not, it’s AUX.
Should I be worried when I see AUX on my thermostat?
Not usually. Seeing it during a cold snap or right after you changed the temperature is completely normal. It’s more worth paying attention to if it’s running for long stretches when the weather’s mild, or if it seems to be on constantly that’s usually a sign something else needs a look.
What can cause AUX heat to run too much?
A few common culprits: a dirty air filter restricting airflow, low refrigerant from a leak, a thermostat that isn’t calibrated correctly, or a heat pump that’s simply undersized for the home. Any of these can make your system reach for backup heat more than it should.
Does AUX heat cost more to run?
Yes, typically. Electric auxiliary heat works like a space heater it’s effective, but it uses a lot more electricity than your heat pump running on its own. If you notice AUX cycling on frequently, it’s worth finding out why, since it can show up on your energy bill fast.
How do I stop my system from switching to AUX heat so much?
The easiest fix is adjusting your thermostat in small steps a degree or two at a time instead of cranking it up all at once. Beyond that, keeping filters clean and staying current on maintenance goes a long way toward keeping your heat pump doing the work on its own.
Does AUX heat show up differently on Nest, Ecobee, or Honeywell thermostats?
The idea’s the same across brands, though the wording can differ slightly. Honeywell thermostats typically show an “Aux Heat” indicator. Nest labels it “Aux” or references it under heat pump/balance settings. Ecobee shows it as part of the Aux/Emergency heat configuration. If you’re not sure what you’re looking at, checking your specific thermostat’s settings menu will confirm it.
