You wake up on a cold Arkansas morning, walk past the thermostat, and suddenly see two words that make you wonder whether your HVAC system is sending a distress signal:
AUX HEAT.
Before you start pricing a new heat pump, there is good news. Seeing auxiliary heat on your thermostat does not automatically mean something is wrong.
For homeowners in North Little Rock, Little Rock, Sherwood, Maumelle, Jacksonville, and surrounding Central Arkansas communities, AUX heat often appears when temperatures drop and your heat pump needs a little extra help keeping the house comfortable.
The important question is not simply “Why is my AUX heat on?”
It is: “How long has it been running, and is my heat pump still doing what it should?”
What Does AUX Heat Mean on a Heat Pump?
AUX heat means your heat pump has activated a secondary source of heat to help reach the thermostat setting.
Most of the time, the heat pump itself handles the majority of your home's heating. It moves heat from the outdoor air into your home rather than generating all of its heat directly.
When outdoor temperatures get colder or the thermostat needs to recover several degrees quickly, the system may activate supplemental heat.
In many electric heat-pump systems, that supplemental source is electric resistance heat.
So when the thermostat displays AUX HEAT, your HVAC system is essentially saying:
"I'm working on it, but I'm bringing in backup."
Is It Normal for AUX Heat to Come On During an Arkansas Cold Snap?
Yes. Short periods of auxiliary heat can be completely normal when outdoor temperatures fall or when the system is recovering from a significant temperature change.
Central Arkansas winters are famous for temperature swings. Homeowners in Lakewood or Park Hill may enjoy a fairly mild afternoon and wake up to temperatures much colder the following morning.
A heat pump that handled yesterday's weather easily may need supplemental heat during that sudden cold period.
Auxiliary heat may also operate briefly while a heat pump goes through its normal defrost cycle. During defrost, the system temporarily changes operation to remove frost from the outdoor coil, and supplemental heat may activate to help maintain indoor comfort.
Federal heat-pump guidance notes that auxiliary heating may operate during colder conditions and during defrost.
That is usually normal behavior.
Why Is My AUX Heat Running Constantly?
AUX heat running for long periods can mean the weather is very cold, but it can also indicate that the heat pump needs attention.
Possible reasons include restricted airflow, a dirty filter, thermostat problems, an outdoor-unit issue, incorrect control settings, or a heat pump that is struggling to provide enough heating on its own.
For a homeowner in Indian Hills, Levy, Argenta, Sherwood, or Jacksonville, the first clue may be that the home still does not feel warm even though AUX HEAT seems to stay on.
That is when it makes sense to have the system checked.
ENERGY STAR recommends inspecting HVAC filters monthly during heavy-use periods because dirty filters restrict airflow and make heating equipment work harder.
Does AUX Heat Use More Electricity?
Electric auxiliary heat can use significantly more electricity than the heat-pump portion of the system.
A heat pump moves heat instead of creating all of it through electric resistance, which is one reason heat pumps can be very efficient.
ENERGY STAR notes that heat pumps can provide efficient winter heating and recommends keeping heat-pump thermostats at a steady comfortable temperature rather than making large setbacks.
When electric resistance backup heat operates, however, energy use can increase.
That is why a thermostat displaying AUX heat for a few cold hours is very different from one showing AUX heat day after day.
If your electric bill suddenly jumps while AUX heat seems to be running constantly, it is worth having the system evaluated.
Can Changing the Thermostat Cause AUX Heat to Come On?
Yes. Raising the thermostat several degrees at once can cause some systems to bring on auxiliary heat to reach the new temperature more quickly.
This can happen when someone comes home and moves the thermostat from 65°F to 72°F all at once.
ENERGY STAR recommends maintaining a relatively steady temperature with heat pumps rather than using the large temperature setbacks commonly associated with furnaces.
In other words, your heat pump often prefers:
“Let's maintain 70.”
rather than:
“Surprise! We need seven degrees right now.”
What Is the Difference Between AUX Heat and Emergency Heat?
Auxiliary heat and emergency heat are not the same thing.
AUX heat normally comes on automatically when the thermostat or heat-pump controls determine additional heating is needed.
Emergency heat is generally a manually selected mode designed to bypass normal heat-pump operation and rely on backup heating.
You should not normally switch to emergency heat simply because the weather is cold.
If the heat pump itself has failed and a technician instructs you to use emergency heat temporarily, that is a different situation.
If you are unsure why your thermostat says EM HEAT, call Sanders Plumbing HVAC before assuming it needs to stay there.
Why Is My Heat Pump Running Constantly in Cold Weather?
Heat pumps often operate for longer cycles than gas furnaces.
That does not necessarily mean something is wrong.
A heat pump typically delivers heat more gradually and maintains a steady indoor temperature rather than producing short bursts of extremely hot air.
During a Central Arkansas cold snap, a heat pump in North Little Rock, Maumelle, Cabot, or Conway may run for long stretches.
The bigger concern is when it runs continuously and the home still cannot reach the thermostat setting, especially if AUX heat is also running constantly.
That may indicate airflow problems, equipment trouble, thermostat issues, or another condition that needs diagnosis.
Can a Dirty Air Filter Make AUX Heat Run More?
It can contribute.
A dirty filter restricts airflow through the HVAC system. ENERGY STAR says dirty filters make heating and cooling systems work harder and can contribute to higher energy use and premature equipment failure.
If the heat pump cannot move enough heated air throughout the home, maintaining the thermostat setting becomes more difficult.
During winter, check the filter regularly—especially during periods when the heat is running heavily.
When Should I Call for Heat Pump Repair in North Little Rock?
Call an HVAC professional if:
AUX heat seems to run almost continuously even during moderate weather, the home will not reach the thermostat setting, the outdoor unit is heavily iced over and does not clear itself, airflow feels unusually weak, the system makes new noises, or your energy use suddenly increases without an obvious explanation.
A little AUX heat during a cold morning may be perfectly normal.
A system begging for backup every day deserves a closer look.
Heat Pump Repair and Maintenance in Central Arkansas
Whether you live in Park Hill, Lakewood, Indian Hills, Levy, Argenta, or elsewhere in North Little Rock, winter heating problems rarely become more convenient by waiting.
Sanders Plumbing HVAC provides heat-pump and heating service throughout Central Arkansas, including Little Rock, Sherwood, Maumelle, Jacksonville, Cabot, Conway, Benton, and Bryant.
Regular heating maintenance can also help identify airflow, electrical, thermostat, and equipment issues before the next cold front arrives. ENERGY STAR recommends annual pre-season HVAC maintenance to help prevent future problems and maintain system performance.
If AUX heat comes on occasionally, your system may simply be doing its job.
If AUX heat has apparently moved in permanently, give Sanders a call.
Frequently Asked Questions About AUX Heat
Is AUX heat bad?
No. Auxiliary heat is a normal feature of many heat-pump systems. Frequent or continuous AUX operation outside very cold conditions may deserve professional inspection.
At what temperature does AUX heat come on?
There is no single temperature that applies to every heat pump. System design, thermostat controls, equipment capacity, outdoor temperature, and heating demand all affect when auxiliary heat activates.
Should I turn AUX heat off?
Normally, no. AUX heat is controlled automatically. If you believe it is operating excessively, have the system inspected rather than disabling an important backup-heating function.
Why does AUX heat come on after I raise my thermostat?
A large thermostat increase may tell the controls that additional heating is needed quickly, causing auxiliary heat to activate.
Does AUX heat mean my heat pump is broken?
Not necessarily. AUX heat can operate normally during cold weather, thermostat recovery, or defrost. Continuous operation combined with poor heating performance can indicate a problem.
Meta Description: Why does your heat pump say AUX heat? Learn when auxiliary heat is normal, why it may run constantly, how it affects energy use, and when to call for heat pump repair in North Little Rock and Central Arkansas.