Why Your Heat Pump Runs Constantly in Cold Weather: Causes, Efficiency Tips, and What to Do

Heat pumps are vital for efficient home heating, but many homeowners notice their heat pump runs constantly when temperatures drop. This extended operation can be normal or indicate a system issue. This article explores why heat pumps run non-stop in cold weather, how to distinguish normal behavior from problems, and practical tips to improve efficiency and comfort.

Table: Common Causes And Solutions For Constantly Running Heat Pumps

Cause	Is It Normal?	Potential Solutions
Design In Cold Temperatures	Yes	Increase insulation, add weather stripping
Dirty Filters Or Coils	No	Replace or clean filters and coils regularly
Improper Sizing Or Installation	No	Have an HVAC pro perform a load calculation
Low Refrigerant	No	Repair leaks, recharge refrigerant
Thermostat Issues	No	Upgrade thermostat or recalibrate settings
Extreme Weather	Yes	Consider supplemental heating for rare cold snaps

How Heat Pumps Work In Cold Weather

Heat pumps operate by transferring heat from the outside air into your home, even in winter. Unlike furnaces, they don’t create heat, but move existing heat. As outdoor temperatures fall, there is less heat to extract, so the unit must run longer to maintain the indoor set temperature.

Modern heat pumps are designed to operate efficiently in most U.S. climates. However, during extended periods of freezing temperatures, it is normal for the system to run continuously.

Normal Operation Versus Signs Of Trouble

What Is Considered Normal?

In mild or moderate cold, heat pumps cycle on and off regularly. In sustained cold—below 35°F—the unit may run nearly non-stop, especially if your thermostat is set high or the home has poor insulation.

This continuous operation helps prevent the interior temperature from dropping too low. Supplemental heat sources, known as “auxiliary” or “emergency heat,” may occasionally kick in during extreme cold.

When It Signals A Problem

If your heat pump never cycles off in mild weather, fails to reach the thermostat set point, or energy bills spike unexpectedly, a problem might be present.

• Dirty filters or coils can restrict airflow
• Low refrigerant may hinder heat transfer
• Improperly sized systems cannot keep up with demand
• Thermostat malfunctions or wiring issues may cause incorrect operation

Common Reasons Heat Pumps Run Constantly In Cold

Cold Climate Design Limitations

Standard air-source heat pumps lose efficiency when outdoor temperatures fall below 32°F. Many units are sized for average winter conditions, but might run constantly when exposed to unusually low temperatures or wind chills.

Insufficient Home Insulation

Air leaks around doors, windows, and ductwork can also cause the system to struggle to maintain warmth.

Dirty Air Filters Or Indoor Coils

Neglecting routine filter changes and coil cleaning can reduce airflow, forcing the heat pump to run longer. Restricted airflow also increases wear and may decrease the lifespan of the compressor.

Thermostat Settings And Location

A thermostat set higher than 68°F will cause the heat pump to run longer, especially in extreme cold. If the thermostat is placed near drafts, sunlight, or heat sources, it may register incorrect readings and keep the unit running.

Incorrect Heat Pump Sizing And Installation

An improperly sized or poorly installed heat pump may never satisfy the thermostat setting during cold weather. A professional can assess whether your system matches your home’s heating load requirements.

Mechanical Or Refrigerant Issues

Low refrigerant, compressor problems, or valve failures prevent your heat pump from extracting and moving enough heat. If you notice ice build-up, strange noises, or poor heating, a technician’s inspection is recommended.

How To Tell If Your Heat Pump Is Working Correctly In Cold Weather

• Check if your thermostat is displaying the correct room temperature.
• Place your hand over a vent—warm air should blow gently, though not as hot as a furnace.
• Your heat pump should keep your home within 2-3 degrees of your set point, even if it runs almost constantly in the cold.
• If the system fails to keep up when temperatures are 30°F or above, consider an evaluation.
• Look for warning lights, error messages, and an unusual rise in energy bills.

Energy Efficiency Of Heat Pumps In Winter

Heat pumps are among the most energy-efficient home heating options in America, even in winter. They use electricity to move heat from outside air to indoors, consuming less power than electric furnaces or resistance heating.

However, their efficiency (measured as HSPF or COP) decreases as outdoor temperatures drop since extracting heat becomes more difficult. In cold snaps, some systems switch to backup heating coils temporarily, increasing energy costs.

Maximizing Your Heat Pump’s Performance In Cold Weather

Set The Thermostat For Best Results

• Set your thermostat to a steady, energy-efficient setting (68°F is recommended by the Department of Energy).
• Avoid raising the temperature by more than 2 degrees or using the ‘emergency heat’ mode except in severe weather.
• If you have a programmable thermostat, allow gradual temperature changes.

Improve Insulation And Seal Leaks

• Upgrade attic and wall insulation for better heat retention.
• Add weather stripping to doors and caulk window frames.
• Seal ductwork and consider window coverings at night for added efficiency.

Keep Filters And Coils Clean

• Replace air filters every 1–3 months during peak heating season.
• Schedule professional maintenance for coil cleaning and refrigerant checks annually.

Check Outdoor Unit

• Clear leaves, snow, and debris from around the outside unit to maintain airflow.
• Ensure the unit is elevated above expected snow lines.

When To Call A Professional

If your heat pump runs constantly but your home never gets warm, blows cold air, or makes loud noises, it’s time for professional service. An HVAC specialist can:

• Assess refrigerant levels and recharge or repair leaks
• Diagnose sensor and thermostat problems
• Check compressor and reversing valve performance
• Evaluate whether the unit is properly sized for your home

Auxiliary And Emergency Heat: What Are They?

Auxiliary Heat

When outside temperatures drop below the heat pump’s efficient range, backup electric resistance (‘auxiliary heat’) automatically activates. This helps maintain temp but consumes significantly more electricity.

Emergency Heat

If the outdoor unit malfunctions, ‘emergency heat’ can be manually enabled, disabling the heat pump and using only electric coils or a gas furnace. Use this mode only when the heat pump is not working, as it is more expensive.

Cost Implications Of Constant Operation

Running your heat pump continuously in very cold weather will increase your electricity bills, but it is often still cheaper than electric resistance heating or oil furnaces.

Heating Method	Estimated Efficiency (COP)	Common Scenarios
Heat Pump (Above 32°F)	2.5-3.5	Normal operation
Heat Pump (Below 20°F, with Aux Heat)	1.0-2.5	During deep freezes
Electric Furnace	1.0	Backup/emergency

Upgrading To A Cold-Climate Heat Pump

Cold-climate or low-ambient heat pumps feature improved compressors and refrigerants that perform reliably in low temperatures (as low as -5°F). Homeowners in northern states or exposed locations may benefit from upgrading for better comfort and efficiency.

Frequently Asked Questions

How Long Should A Heat Pump Run In Freezing Weather?

It is normal for a heat pump to run most or all of the time when outdoor temperatures are below 32°F. If it maintains the set point, there’s likely no problem.

Can Running Constantly Damage My Heat Pump?

Modern units are designed for extended operation without harm, though neglected maintenance or mechanical faults can cause accelerated wear and damage.

Should I Run Auxiliary Or Emergency Heat?

Allow the system to switch to auxiliary heat automatically. Use emergency heat manually only if the outdoor unit is disabled and you need a temporary heat source.

Does A Heat Pump Work In Extreme Cold?

Standard units function well in moderate cold, but below 20°F, backups may be necessary. Choose a cold-climate heat pump for best performance in harsh winters.

What Temperature Should I Set My Thermostat In Winter?

The Department of Energy recommends 68°F for heating—this keeps energy costs lower and reduces stress on your system.

Quick Troubleshooting Checklist

• Change or clean filters every month during heating season.
• Clear snow, ice, or debris from the outdoor unit.
• Check thermostat settings and program for optimal use.
• Ensure all vents are open and unblocked.
• Monitor temperature differences at each room vent.
• Schedule professional maintenance each fall before cold weather hits.

When To Add Supplemental Heating

Homeowners in areas subject to prolonged sub-freezing temperatures may need additional heating sources such as ductless mini-splits, wood stoves, or backup electric heaters for comfort during rare cold snaps.

Consult with an HVAC contractor to design the most efficient solution for your specific climate and home layout.

Key Takeaways For Heat Pump Owners

• Constant running is usually normal in cold weather if your home stays comfortable and energy bills are manageable.
• Regular maintenance, good insulation, and correct thermostat programming are crucial to maximize performance.
• Call a professional for continual operation outside of extreme cold, heating failures, or rising costs.
• Explore cold-climate heat pumps or supplemental heating for severe winters.

By understanding why your heat pump runs constantly in cold weather and implementing these best practices, you can improve efficiency, comfort, and peace of mind throughout the heating season.