A heat pump running constantly in winter is usually normal, not a sign of failure
Heat pumps work differently in cold weather than in warm weather. In winter, your heat pump may run almost all day and night without stopping, and this does not mean it is broken or working inefficiently. A heat pump that runs constantly is often doing exactly what it should do — moving heat from outside air into your home, even when outdoor temperatures are well below freezing.
The reason is straightforward: heat pumps have a lower heating capacity in winter than in summer. When it is 20 degrees outside, your heat pump has to work much harder to extract enough heat to warm your home than it does when it is 50 degrees outside. To meet your home's heating demand, it runs longer and more often. This is normal operation, not a malfunction.
However, constant running can also signal a problem — usually that your heat pump is undersized for your home, your thermostat is set too high, or your backup heating system is not working. Understanding the difference between normal winter operation and a genuine issue will help you decide whether to call a technician or straightforward adjust your expectations.
Key Takeaways
- Heat pumps naturally run more often in winter because outdoor air is colder and contains less heat to extract, so constant operation is usually normal.
- A heat pump running constantly while your home stays cold, or your electric bill spikes sharply, suggests the unit may be undersized or malfunctioning.
- Backup electric heating (called auxiliary or emergency heat) is designed to run alongside your heat pump on very cold days and will increase your energy use noticeably.
- Thermostat settings, insulation quality, and outdoor temperature all affect how often your heat pump runs, so adjusting one of these may reduce runtime without sacrificing comfort.
- Most heat pumps operate efficiently down to about 32 degrees; below that, they work harder and run longer, which is expected behavior.
How heat pumps heat differently in winter versus summer
In summer, your heat pump cools by moving heat from inside your home to outside air. In winter, it reverses and moves heat from outside air into your home. The problem is that cold air contains far less heat than warm air. At 70 degrees outside, there is plenty of heat to extract. At 20 degrees, there is much less, so the heat pump has to run much longer to gather enough heat to warm your home by one degree.
This is why a heat pump that runs for 30 minutes per hour in mild winter weather might run for 50 or 60 minutes per hour when it is very cold. The unit is not failing — it is working at full capacity to meet your heating demand. The colder the outdoor temperature, the longer the runtime will be. At some point, usually around 32 degrees or below, many heat pumps also turn on a backup electric heating element (called auxiliary heat or emergency heat) to help keep up with demand. When that element is running, your electric bill will rise noticeably because electric resistance heating is expensive.
Understanding this difference helps you recognize what is normal. If your heat pump runs constantly when it is 25 degrees outside, that is expected. If it runs constantly when it is 45 degrees outside and your home is still cold, that is a problem.
When constant running means something is wrong
Constant operation becomes a concern when one of three things is true: your home is not reaching your set temperature, your electric bill has jumped far beyond what you expected, or your heat pump is running but your home is actually getting colder.
An undersized heat pump is the most common cause. If a contractor installed a unit that is too small for your home's square footage or insulation quality, it will run constantly in winter and still not keep up with demand. You can check your unit's capacity (measured in BTU, or British thermal units) against your home's heating load — a heating contractor can calculate this, or you can find the BTU rating on the outdoor unit's nameplate and compare it to sizing charts for your climate zone. If the unit is significantly undersized, constant running is the symptom, and replacement or supplemental heating is the solution.
A malfunctioning compressor or refrigerant leak will also cause constant running without adequate heating. If your heat pump runs all day but your home stays 5 or 10 degrees below your thermostat setting, call a technician. The unit may need repair or recharge. A clogged outdoor coil (from ice, dirt, or debris) can also reduce heating capacity and force longer runtimes. If you see ice buildup on the outdoor unit during operation, that is a sign the defrost cycle is not working properly.
Finally, check your thermostat setting. If you have set it to 75 degrees in a home that was previously heated to 68 degrees, the heat pump will run much longer than usual to close that gap. Lowering the setpoint by a few degrees will reduce runtime and lower your bill without sacrificing much comfort.
The role of backup heating and why it increases your bill
Most modern heat pumps include a backup electric heating element that turns on automatically when outdoor temperatures drop below a certain threshold — usually 32 to 40 degrees, depending on the unit and your thermostat settings. This element is called auxiliary heat, emergency heat, or supplemental heat. It is not a sign of failure; it is a design feature meant to help the heat pump keep up on very cold days.
However, electric resistance heating is expensive. It uses roughly three times as much electricity as the heat pump itself to produce the same amount of warmth. When your backup heat is running, you will notice your electric bill climb. Some thermostats display an indicator light or message when auxiliary heat is active, so you can see when it is running. If you want to reduce its use, you can lower your thermostat setpoint slightly, improve your home's insulation, or seal air leaks around doors and windows.
Some homeowners disable auxiliary heat to save money, but this is not recommended. If you turn it off, your heat pump alone may not be able to keep your home warm on the coldest days, and your home temperature will drop. The backup element exists for a reason — to maintain comfort when the heat pump reaches its limit.
What affects how often your heat pump runs in winter
Several factors determine whether your heat pump will run constantly or cycle on and off. Outdoor temperature is the biggest one: the colder it is, the longer the runtime. But you can also influence runtime by adjusting thermostat settings, improving insulation, and reducing air leaks.
Your thermostat setpoint directly affects runtime. Every degree you lower the setpoint reduces the amount of heat your home needs and shortens the time the heat pump must run. Lowering the setpoint from 72 to 70 degrees can reduce winter runtime by 10 to 15 percent. You can also use a programmable or smart thermostat to lower the temperature when you are away or asleep, which saves energy without sacrificing comfort when you are home.
Insulation and air sealing also matter. A home with poor insulation or drafty windows and doors loses heat faster, so the heat pump has to run longer to maintain temperature. Sealing air leaks around baseboards, outlets, and window frames, and adding insulation to the attic, can reduce heating demand and shorten runtime. These improvements also reduce your overall heating bill, whether you use a heat pump or any other heating system.
Finally, the age and efficiency rating of your heat pump affects runtime. Older units or those with lower SEER and HSPF ratings (heating seasonal performance factor) are less efficient and will run longer to produce the same heat. If your heat pump is more than 15 years old and runs constantly, upgrading to a newer, more efficient model may reduce runtime and lower your bill.
How to tell if your heat pump is working efficiently in winter
The best way to assess whether your heat pump is working as it should is to compare your actual electric bill to what you expected based on your heating needs and local utility rates. Most utilities provide historical usage data online, so you can see how much electricity you used last winter at the same outdoor temperatures. If this winter's usage is similar, your heat pump is likely working normally. If it is significantly higher, something may be wrong.
You can also monitor your heat pump's runtime manually. On a day when outdoor temperatures are steady (not rising or falling), note what time your heat pump turns on and off. If it runs for 45 minutes and then cycles off for 15 minutes, that is normal. If it runs for 8 hours straight without stopping, even on a mild day above 40 degrees, that suggests a problem worth investigating.
A professional energy audit can also reveal whether your heat pump is sized correctly and whether your home's insulation or air sealing is limiting efficiency. Many utility companies offer these audits for free or at a reduced cost. The audit will show you exactly where heat is escaping and what improvements would have the biggest impact on your heating bill.
Comparing heat pump winter operation to other heating systems
Heat pumps behave differently from furnaces and boilers in winter, which can surprise homeowners switching from a traditional system. A gas furnace cycles on and off — it runs for 10 or 15 minutes, then stops for 30 minutes while the house coasts on stored heat. A heat pump, by contrast, often runs much longer and more continuously, especially in cold weather. This does not mean it is less efficient; it means it operates on a different principle.
Heat pumps are most efficient when they run continuously at a steady output, rather than cycling on and off. A heat pump running constantly at 50 percent capacity uses less energy than one that cycles on and off at full capacity. So if your heat pump runs for 8 hours straight on a cold day, it may actually be more efficient than a furnace that cycles on and off during the same period.
However, heat pumps do have a lower efficiency threshold. Below about 32 degrees, most air-source heat pumps lose efficiency rapidly. At 0 degrees, they may use nearly as much electricity as a backup electric heater to produce the same warmth. In climates where temperatures regularly drop below 20 degrees, a ground-source heat pump (which draws heat from the ground rather than the air) is more efficient, but it is also much more expensive to install. For most homeowners in cold climates, an air-source heat pump with backup electric heating is the practical choice.
Steps to reduce constant running without sacrificing comfort
If your heat pump is running constantly and you want to reduce runtime and lower your bill, start with these low-cost adjustments before calling a technician.
Lower your thermostat setpoint by 2 to 3 degrees. You may not notice the difference in comfort, but your heat pump will run significantly less. If you are away during the day, lower it further while you are out.
Seal air leaks around windows, doors, and baseboards. Use weatherstripping, caulk, or foam sealant to close gaps. This reduces the amount of heat your home loses and shortens runtime.
Close doors to unused rooms. Heating only the spaces you occupy reduces the total heating load on your heat pump.
Check your outdoor unit for ice or debris. If the coil is clogged or frozen, the heat pump cannot extract heat efficiently. Clear away snow and ice, and make sure the unit has at least 2 feet of clearance on all sides.
Use a programmable or smart thermostat. These allow you to set different temperatures for different times of day, so you heat only when needed.
If you have made these adjustments and your heat pump still runs constantly while your home stays cold, or your electric bill remains very high, contact a technician. The unit may need servicing, or it may be undersized for your home.
Frequently Asked Questions
Is it normal for a heat pump to run 24 hours a day in winter?
Yes, on very cold days (below 20 degrees) it is normal for a heat pump to run almost continuously. The colder the outdoor air, the longer the runtime. If your home is reaching your thermostat setpoint and your bill is in line with expectations, constant running is not a problem. If your home is cold despite constant running, the unit may be undersized or malfunctioning.
Why is my electric bill so high when my heat pump runs constantly?
Constant running in winter is expensive because your heat pump is working at full capacity to meet heating demand. If your backup electric heating is also running, your bill will be even higher — electric resistance heating costs roughly three times as much as heat pump heating. Lowering your thermostat setpoint, sealing air leaks, and improving insulation will reduce both runtime and cost.
Should I turn off my heat pump and use only backup heat in winter?
No. Your heat pump is more efficient than backup electric heating, even in cold weather. Running the heat pump alongside backup heat uses less total electricity than backup heat alone. Turning off the heat pump to save money will actually increase your bill and may leave your home uncomfortably cold.
How do I know if my heat pump is too small for my home?
An undersized heat pump will run constantly but fail to reach your thermostat setpoint, even with backup heat running. If your home stays 5 degrees or more below your setpoint on cold days, the unit is likely undersized. A heating contractor can calculate your home's heating load and compare it to your unit's capacity to confirm. Replacement or supplemental heating may be necessary.
Can I reduce heat pump runtime by using a higher thermostat setpoint?
No — a higher setpoint will increase runtime, not reduce it. The heat pump will run longer to reach and maintain a higher temperature. To reduce runtime, lower your setpoint instead. You can also use a programmable thermostat to lower the temperature when you are away or asleep.