Why Your Heat Pump Is Struggling During Cold Weather

This is one of the most common questions we hear.

A heat pump typically delivers air around 90–100°F, which is warm enough to heat your home but feels lukewarm compared to a gas furnace that blows 120–140°F air. When it’s very cold outside, that difference becomes more noticeable, especially if your home has older insulation or air leaks.

Common Causes of Heat Pump Heating Problems

Backup Heat Strips Not Working Properly

Heat pumps rely on electric heat strips as backup heat when outdoor temperatures fall below the system’s efficient operating range.

If those heat strips fail or don’t engage correctly:

• The heat pump alone can’t keep up

• Indoor temperatures slowly fall

• The system runs longer without real comfort improvement

• Energy bills increase as the unit struggles

In the Sandhills, this issue often goes unnoticed because the system does produce some heat—just not enough during colder nights.

Heat Pump Not Working Even If Heat Strips Are On

In some cases, homeowners assume the heat strips are the problem, when the real issue is the heat pump itself. Common causes include:

• Low refrigerant levels or refrigerant leaks

• Dirty or blocked outdoor coils, which are common in sandy or pine-heavy areas

• Compressor or reversing valve problems, preventing proper heat transfer

• Restricted airflow from clogged filters or duct issues

When the heat pump isn’t doing its share of the work, the backup heat has to carry the load alone, dramatically increasing energy usage.

A Sandhills-Specific Issue: Outdoor Coil Buildup

One problem many national HVAC blogs don’t mention is how Sandhills soil, pine needles, and fine dust affect heat pump performance.

Outdoor units in this region often experience:

• Faster coil clogging

• Reduced heat absorption efficiency

• More frequent defrost cycles

This buildup limits the system’s ability to pull heat from the air, even when temperatures are technically within the heat pump’s operating range.

Why DIY Fixes Often Miss the Real Problem

Heat pump systems are complex. Turning up the thermostat or replacing a filter may help temporarily, but it won’t identify whether:

• The backup heat strips are actually engaging

• The refrigerant charge is correct

• The reversing valve is switching properly

• Airflow meets system requirements

A trained technician can pinpoint which component is failing, whether it’s the heat pump, the backup heat strips, or both—and restore efficient operation.

Auxiliary Heat: The Backup System You May Not Realize You’re Using

Your heat pump has a built-in backup called auxiliary heat (sometimes labeled “AUX” or “EM HEAT” on the thermostat). In Moore County winters, this system is essential.

When auxiliary heat should turn on

Aux heat is designed to kick in automatically when:

• Outdoor temperatures drop too low

• Your indoor temperature falls 2–3 degrees below the thermostat setting

• The system goes into a defrost cycle

When it works properly, auxiliary heat helps your home stay comfortable during cold snaps.

When auxiliary heat causes problems

Homeowners often call us because they notice:

• Higher-than-normal power bills

• Air that feels very dry

• Rooms that feel hot one moment and cool the next

These can all be signs that auxiliary heat is running more than usual. Electric heat strips use significantly more energy than the heat pump itself, so extended cold weather can drive bills up quickly.

When auxiliary heat isn’t working at all

This is where comfort really drops.

If aux heat fails to engage, your home may never reach the thermostat setting, no matter how long the system runs. Common causes include:

• Burned-out heat strips

• Failed sequencers or contactors

• Thermostat wiring issues

• Incorrect lockout settings

When this happens, the unit is left to handle cold temperatures alone, which it simply isn’t designed to do.

Why Defrost Cycles Are More Noticeable in Moore County

Moore County’s cold, humid winter air creates ideal conditions for frost buildup on outdoor heat pump coils.

What a defrost cycle does

When frost builds up, your system temporarily switches into cooling mode to melt it off. During this process:

• The outdoor unit may steam or drip water

• Indoor air can feel cooler

• Auxiliary heat should turn on to balance the temperature

If everything is working correctly, you may barely notice the cycle.

When defrost feels uncomfortable

If auxiliary heat is weak or not working, defrost cycles become very noticeable. Homeowners often describe this as:

• Cool air blowing from vents

• Sudden temperature drops

• A system that feels inconsistent

This is especially common during early morning hours when temperatures are lowest.

When Defrost Stops Working Properly

In some cases, the defrost system itself is the problem.

Signs of defrost failure include:

• The outdoor unit covered in ice

• The system running constantly with little heat

• The unit getting stuck in defrost mode

Common causes are:

• A failed defrost control board

• Faulty temperature or coil sensors

• Electrical issues preventing proper switching

When this happens, the it loses efficiency quickly and can even shut down to protect itself.

When to Call for Heat Pump Service

You should schedule professional service if you notice:

• The system runs constantly but never feels warm

• Indoor temperatures drop overnight

• Sudden spikes in winter energy bills

• Cool or barely warm air from vents

• The system switching to emergency heat frequently

Addressing these issues early can prevent unnecessary strain on your system and help extend its lifespan.

Keeping Your Home Comfortable and Efficient All Winter

Heat pumps can work very effectively in the Sandhills NC climate but only when every component is functioning properly and the system is maintained for local conditions.

Routine inspections, coil cleanings, and electrical checks ensure your heat pump and backup heat work together as intended, keeping your home warm without driving up energy costs.

If your heat pump is struggling to keep up this winter, professional diagnostics can help restore comfort and efficiency before small issues turn into major repairs.

A Final Word for Moore County Homeowners

Heat pumps are efficient, reliable systems but they are still mechanical equipment that reacts to weather, humidity, and wear over time. Cold snaps like we’re seeing around Pinehurst tend to expose weaknesses that stay hidden during mild winters.

Get the Best Heat Pump Service in the Sandhills

If your heat pump feels like it’s struggling, there’s usually a clear explanation and often a fix. Understanding how your system works in cold weather puts you in a much better position to know when to wait it out and when it’s time to call for help.

Call Air Comfort Haeting and Air at 910-695-8241 today if your heat pump isn’t keeping up or contact us online with any questions. We’ll get your home warm and your bills under control.