Should My Heat Pump Run All the Time?

Short answer

Not always, but often a heat pump runs for long stretches and that can be perfectly normal. Heat pumps deliver heat gradually, so in cold or very hot weather they may run for hours. Constant running becomes a concern when the weather is mild, the house is not reaching the set temperature, or your energy bills jump without explanation.

Why long run times can be normal

A furnace puts out a lot of heat in short bursts and then shuts off. A heat pump typically works at a lower output for longer periods. Two things influence how it behaves:

• Single-stage systems are either on or off. They tend to cycle on and off in mild weather and run longer as the weather gets more extreme.
• Variable-speed (inverter) systems adjust their output up and down. These may run almost continuously at a low speed, which is how they are designed to work.

Outdoor temperature matters too. The bigger the gap between the outdoor temperature and your thermostat setting, the longer the system has to run. Heavy use during a cold snap or heat wave is usually expected.

How many hours a day is normal?

There is no single correct number. Run time depends on your climate, the size of the system, how well the home is insulated, and the type of heat pump. On a mild day you might see it run a small fraction of the day, and on an extreme day it may run most or all of it. If you want a useful benchmark, compare your system against itself: how long does it run in similar weather compared with previous seasons? A sudden change is more telling than any one number.

Is it cheaper to leave it on or set it back?

Many manufacturers and efficiency programs suggest holding a steady temperature rather than making big swings, because a large setback can force the system, and possibly the electric backup heat, to work hard to recover. Savings from a small, modest setback may still be real, but large changes can backfire on a heat pump. If your thermostat shows a recovery message after a schedule change, our article on heat pump recovery mode explains what is happening.

A practical approach: pick a comfortable temperature, avoid dramatic schedule swings, and check your bills over a few weeks rather than a few days.

How to tell whether your heat pump is working correctly

Signs of normal operation:

• The home reaches and holds the set temperature, even if it takes a while.
• Air from the vents feels warm in heating mode (it is often cooler than furnace air, which is normal) or cool in cooling mode.
• The outdoor unit runs, and occasionally defrosts in cold, damp weather, with some steam from the unit (see is it normal for a heat pump to steam).
• It does not trip breakers or make loud grinding or banging noises.

Signs of a possible problem:

• The system runs continuously but the house never reaches the set temperature.
• Mild weather and non-stop running together.
• The outdoor unit is covered in ice and does not clear.
• Airflow from the vents is weak.
• Auxiliary or emergency heat appears to be running much of the time. See when to use emergency heat.

Reasons a heat pump runs constantly when it should not

• Dirty air filter or blocked vents, which restrict airflow.
• Thermostat settings that are too extreme, or a thermostat that is not reading correctly.
• Dirty indoor or outdoor coils.
• Air leaks and poor insulation, so heat escapes as fast as it is made.
• An undersized system that cannot keep up with the home’s load.
• Low refrigerant or a failing component, which reduces capacity. See how to tell if a heat pump is low on refrigerant.
• Open windows, doors or a very large temperature setback.

Checks you can do safely

1. Set the thermostat to a reasonable temperature and confirm it is on the correct mode.
2. Replace or clean a dirty air filter, following the manufacturer’s instructions.
3. Make sure supply and return vents are open and not blocked by furniture.
4. Clear leaves, snow or debris from around the outdoor unit, without poking into it.
5. Confirm that doors and windows are closed.

Turn the power off at the thermostat and the disconnect or breaker before doing anything near the unit. Do not open panels or touch wiring.

What temperature to set in summer

Comfort preferences vary. Many people choose a setting in the mid-70s Fahrenheit while at home, and a few degrees higher when away, but the right number depends on your home and budget. Avoid setting it dramatically lower than you need, because the system will simply run longer without cooling faster.

When to call a professional

Call a licensed HVAC technician if:

• The system runs constantly but cannot keep the house comfortable.
• You suspect a refrigerant leak (oily residue, hissing, or ice on lines). Handling refrigerant requires certification.
• Breakers trip repeatedly, or you notice burning smells or visible damage. Turn the system off and do not keep resetting the breaker.
• The outdoor unit stays iced over.

Electrical and refrigerant work is not a DIY job.

Related questions

If long run time is tied to your fan setting, see heat pump fan: on or auto. If you have a ground-source system, read about geothermal heat pump troubleshooting.