Why Your Heat Pump Might Struggle To Keep Up With The Cold Weather

Why Your Heat Pump Might Struggle To Keep Up With The Cold Weather

Heat pumps are a great fit for many homes in Charlottesville, VA and the surrounding areas because they deliver efficient heating for much of the year. But when temperatures drop, some homeowners notice their heat pump running longer, blowing cooler air than expected, or failing to maintain the thermostat setting.

If you are asking, “Why is my heat pump not keeping up in cold weather?”, the answer is often a mix of normal heat pump behavior and fixable issues. Below are the most common reasons a heat pump struggles during winter, along with practical steps you can take to improve comfort and lower energy costs.

1) Cold weather reduces a heat pump’s heating capacity

A heat pump does not create heat like a furnace. It moves heat from outside air to inside your home. When outdoor temperatures fall, there is less heat available to move, and the system must work harder to extract it. As a result, heating capacity can drop and run times increase.

What this looks like at home

• Your system runs for long stretches, sometimes continuously during a cold snap.
• The air from vents feels “cooler” than furnace air, even though it is still warming the home.
• Your thermostat temperature rises slowly or stalls a degree or two below the setpoint.

Tip: Check your thermostat setting and avoid large temperature jumps. Raising the thermostat 3 to 5 degrees at once can trigger auxiliary heat and increase energy use.

2) Auxiliary heat is working, but it may be expensive

Most heat pumps in Central Virginia include auxiliary (backup) heat, often electric heat strips. Auxiliary heat helps when outdoor temperatures are low or when the heat pump cannot keep up. It is normal for auxiliary heat to run occasionally, but frequent use can drive up your power bill.

How to tell if auxiliary heat is on

• Your thermostat displays “AUX” or “EM HEAT.”
• Energy bills increase sharply during cold weeks.
• Indoor air feels warmer, closer to a traditional furnace feel.

Tip: If AUX heat is on constantly, schedule a professional heat pump service. The system may have an airflow problem, low refrigerant, or a control issue that is forcing backup heat unnecessarily.

3) Your heat pump may be undersized or your home needs more insulation

Sometimes the equipment is operating correctly, but the house loses heat faster than the heat pump can replace it. This is common in older homes around Charlottesville with limited attic insulation, leaky windows, or unsealed ductwork.

Common heat loss culprits

• Insufficient attic insulation or attic air leaks
• Drafty doors and windows
• Leaky or poorly insulated ductwork in crawlspaces or attics
• Unsealed penetrations around plumbing, wiring, or recessed lights

Practical step: Start with the basics. Add weatherstripping, seal obvious gaps, and verify attic insulation depth. Many homes benefit dramatically from air sealing and insulation improvements, which help any heat pump perform better in cold weather.

4) Dirty filters and restricted airflow reduce heating performance

Airflow is critical for heat pump heating. A clogged filter, closed registers, or a dirty indoor coil can choke airflow and reduce the system’s ability to deliver heat. In severe cases, restricted airflow can contribute to icing problems and frequent defrost cycles.

Homeowner checklist

• Replace or clean your air filter every 1 to 3 months (more often with pets).
• Keep supply registers open and return grilles unobstructed.
• Make sure furniture, rugs, or curtains are not blocking returns.

Tip: If you replace the filter and still notice weak airflow, it is time for an HVAC technician to inspect the blower, duct system, and indoor coil.

5) Defrost cycles are normal, but excessive defrosting is not

In winter, the outdoor unit can collect frost. Heat pumps periodically run a defrost cycle to melt it. During defrost, the system temporarily switches operation to remove ice, and you may feel cooler air indoors or see steam rising from the outdoor unit. That steam is usually normal.

Signs defrost is becoming a problem

• The outdoor unit is encased in ice for long periods.
• Defrost cycles happen very frequently.
• Heat output indoors drops significantly or you feel cold drafts.

Excessive icing can be caused by low refrigerant charge, a failing defrost sensor, a malfunctioning reversing valve, or airflow issues.

Tip: Keep the outdoor unit clear. Remove leaves, snow, and debris, and maintain at least 18 to 24 inches of clearance around the unit for proper airflow.

6) Refrigerant issues can limit heat transfer

If refrigerant is low due to a leak, your heat pump cannot move enough heat into the home. This can lead to long run times, poor comfort, and in some cases ice buildup on coils. Refrigerant is not a “top-off” situation. If the charge is low, the leak must be found and repaired.

Symptoms that warrant service

• Heat pump runs constantly but struggles to reach the set temperature
• Outdoor unit freezes more than usual
• Unusual hissing sounds near refrigerant lines

Tip: If you suspect a refrigerant problem, turn the system off and call for professional heat pump repair. Continued operation can stress the compressor and increase repair costs.

7) Thermostat settings and controls can unintentionally increase AUX heat

Modern thermostats are powerful, but incorrect settings can cause comfort issues. For example, aggressive “recovery” settings may trigger auxiliary heat more often, and poor thermostat placement can lead to inaccurate temperature readings.

Thermostat tips for winter heat pump performance

• Avoid big setpoint changes. Make small adjustments instead.
• Use a consistent schedule, especially during cold spells.
• Make sure the thermostat is not near drafts, sunlight, or supply vents.

If you recently changed thermostats and noticed worse performance, it may need heat pump specific configuration.

8) Duct leaks and duct design problems can waste heat

Even a high-efficiency heat pump will struggle if the heated air never reaches your living space. Duct leaks in attics or crawlspaces can dump warm air outside the conditioned area and pull in cold air, making your home feel uneven and drafty.

Signs of duct problems

• Some rooms are consistently colder than others
• Dusty home or musty odors when the system runs
• High energy bills with modest comfort

Tip: Ask about duct sealing and airflow balancing. These services can significantly improve heat pump heating in winter and reduce the need for auxiliary heat.

Quick winter maintenance steps you can do today

• Replace the air filter and confirm returns are not blocked.
• Clear the outdoor unit of leaves and debris. Maintain clearance on all sides.
• Check supply vents in cold rooms and keep them open.
• Seal drafts around doors and windows to reduce heat loss.
• Watch the thermostat for frequent “AUX” operation.

When to call Mack Morris Heating & Cooling

Some heat pump behavior in cold weather is normal, but you should schedule service if:

• Your heat pump cannot maintain temperature even on mild winter days
• AUX heat runs almost constantly
• You see heavy ice on the outdoor unit or repeated freeze-ups
• Airflow is weak, rooms are uneven, or the system is noisy

At Mack Morris Heating & Cooling, we help homeowners across Charlottesville, VA and nearby communities troubleshoot heat pump performance, improve efficiency, and restore comfort fast. A professional inspection can identify issues like low refrigerant, airflow restrictions, defrost problems, or duct leakage and recommend the most cost-effective fix.

Stay comfortable all winter

If your heat pump is struggling to keep up with the cold weather, do not assume you need a full replacement. Many winter comfort issues come down to airflow, maintenance, insulation, or controls. With a few homeowner steps and the right HVAC service, your heat pump can deliver reliable heating through the season.

Need help in Charlottesville or surrounding areas? Contact Mack Morris Heating & Cooling to schedule heat pump repair or seasonal maintenance and get your home back to warm, efficient comfort.