Backup heat draws more power
Heat strips create heat directly with electricity, while a heat pump normally moves heat from outdoor air into the home.
Frederick heat-pump FAQ
Is auxiliary heat expensive in Frederick?
Yes, auxiliary heat can get expensive when it runs for long stretches. The AUX HEAT message usually means the heat pump's turned on a backup heat source, often 5 to 15 kilowatts of electric resistance heat strips, to help warm the home.
Seeing AUX HEAT for a short spell on a cold Frederick morning doesn't automatically mean something's wrong. The real question is whether backup heat's running more than the weather and your thermostat settings explain.
Read the pattern
One AUX message does not tell the whole story.
Runtime, weather, thermostat settings, and comfort matter more than the display by itself.
Short assistance can be expected
Cold weather, a thermostat recovery, and a defrost cycle can all bring on AUX HEAT for a limited time.
Long or unusual runtime needs an answer
Frequent backup heat in mild weather, poor comfort, heavy ice, or weak airflow is worth diagnosing.
Why the bill can rise
Auxiliary heat costs more than the normal heat-pump cycle.
A heat pump warms a home by moving heat from outdoor air indoors. The U.S. Department of Energy explains that heat pumps transfer heat rather than generate it, which is why normal operation runs far more efficiently than electric resistance heating.
Resistance strips work differently. Electricity flows through heating elements, and the air handler pushes that heat through the ductwork. It's a useful backup, but it draws a lot of power while it runs.
A federal field study found that excessive auxiliary-heater runtime can be costly and waste energy. Right equipment sizing and the right control settings can cut down unnecessary backup heat use, and we can check both.
What triggers AUX HEAT?
Backup heat can be normal. The runtime is the clue.
The thermostat display doesn't identify the trigger by itself. Look at what the system and the weather were doing at the same time.
The heat pump needs help meeting the load
When outdoor temperatures fall, the heat pump may need backup heat to keep up with the home's heating demand.
A large temperature change asks for a fast recovery
Raising the setting 3 or more degrees at once can call for supplemental heat, depending on the thermostat and its controls.
The outdoor coil is clearing frost
A short AUX cycle during defrost can keep cool air from blowing through the home while the outdoor coil clears.
The heat pump cannot deliver enough heat
Restricted airflow, a control problem, heavy ice, duct limits, or equipment capacity can make backup heat run more than expected.
Defrost deserves context.
Frost can form on the outdoor coil during cold, damp weather. The system periodically reverses operation to clear it, and auxiliary heat may kick in during defrost to keep the indoor temperature steady. That's a short event, and it's not the same as a heat pump that stays on resistance heat most of the day.
Check your own usage
There is no single Frederick price for auxiliary heat.
Homes have different heat-strip capacities, runtimes, electricity suppliers, rate plans, and bill charges. You'll find the heat-strip capacity in the equipment documentation, or we can pull it for you. Don't open electrical panels or remove equipment covers.
Potomac Edison explains that a Maryland electric bill separates electricity supply from delivery and other charges. Its Maryland customer-choice page publishes Standard Offer Service pricing, but your own price may differ. The Maryland bill guide shows where usage and pricing information appear.
When to pay attention
Watch the pattern, not one cold morning.
Short backup operation protects comfort just fine. A heat pump leaning on resistance heat day after day needs a closer look from us.
Short, explained runtime
- AUX HEAT appears briefly during the coldest part of the day.
- The home reaches the thermostat setting and backup heat turns off.
- The message appears during a short defrost event, then normal heat-pump operation returns.
- Comfort and airflow remain steady without unusual noise, odor, breaker trips, or heavy ice.
Long or unexplained runtime
- AUX HEAT runs for long stretches in relatively mild weather.
- The thermostat keeps calling for backup heat while the home falls farther below the setpoint.
- The outdoor unit never seems to run during a heating call.
- The outdoor coil stays heavily encased in ice instead of clearing through normal defrost.
- Electricity use jumps without a matching change in weather or thermostat settings.
These signs don't point to one failed part on their own. A dirty filter, blocked airflow, thermostat setup, sensor problem, control fault, refrigerant-side issue, outdoor-unit problem, duct limitation, or equipment sizing mismatch can all overlap. The NREL study documented a case where a control or outdoor-temperature-sensor fault caused resistance heat to run in relatively mild conditions.
Safe homeowner checks
Reduce unnecessary AUX HEAT without opening the equipment.
Don't disable auxiliary heat or change the equipment's factory settings just to cut a bill. Backup heat may be doing exactly what it should in cold conditions.
Keep the thermostat steady
Avoid pushing the setting up 3 or more degrees at once. A big recovery request is exactly what brings on backup heat.
Check the air path
Look at the filter, supply registers, and return grilles. Replace a dirty filter only with a type that fits the system, and keep vents clear.
Watch the outdoor unit safely
Clear loose leaves or snow blocking airflow, from a safe distance. Don't chip ice off the coil or open the equipment yourself.
Write down the pattern
Note the outdoor temperature, thermostat setting, indoor temperature, and how many minutes AUX HEAT stays on the display.
Thermostat compatibility matters. ENERGY STAR includes resistance-heat utilization among the performance measures for smart thermostats used with heat pumps. A generic setting that works fine for a furnace won't necessarily suit a variable-capacity or multi-stage heat pump, and we set those up differently.
Fast answers
Questions Frederick homeowners ask next.
Should I turn auxiliary heat off?
Don't disable it as a first move. Backup heat supports comfort when the heat pump needs help. Call us to find out why it's running before you touch equipment or installer settings.
Does AUX HEAT always mean the heat pump is broken?
No. AUX HEAT can show up during normal recovery, cold weather, or defrost. A constant or unusual pattern is what deserves a thermostat, airflow, and equipment check from us.
Is emergency heat the same as auxiliary heat?
No. AUX HEAT's generally an automatic call for support. Emergency heat is a thermostat mode that typically stops normal compressor heating and relies fully on the backup source.
Can a dirty filter make auxiliary heat run?
Restricted airflow can cut delivered heat and hurt system performance. Check the filter yourself, but let us diagnose the full operating pattern if AUX HEAT keeps going.
How can I estimate the cost of auxiliary heat?
Multiply the backup heat kilowatts by runtime hours and the electricity price per kilowatt-hour. That estimates the energy charge tied to the heat strips, not the entire electric bill.
When to request service
Let the diagnosis explain the runtime.
Call us for a heat-pump check when auxiliary heat becomes the main heating source, keeps showing up in mild weather, or comes with poor comfort, heavy ice, weak airflow, unusual cycling, or a sharp unexplained usage jump.
Before we visit, jot down the outdoor temperature, thermostat setting, indoor temperature, AUX HEAT runtime, recent filter changes, and any breaker or outdoor-unit behavior. That gives us a cleaner starting point.
Auxiliary heat running more than expected?
Tell us when AUX HEAT appears, what the heat pump is doing at the same time, and whether the home is reaching the setpoint. That points the visit toward setup, airflow, or equipment diagnosis.