The short answer

A heat pump running for hours on a 25 degree night in Northern Virginia is normal. It’s built to run long and steady. Running nonstop on a 50 degree day, showing AUX all day, or never reaching the temperature you set is not.

The part most people don’t know

A heat pump pulls heat out of the outdoor air, and the colder it gets, the less heat there is to pull. DOE’s Building America researchers put it plainly: capacity falls as the outdoor temperature falls. An older single-stage heat pump starts needing backup heat around 30°F, its balance point. Colder than that, it runs nonstop and the backup strips help.

Systems are sized to the local design temperature (DOE’s sizing guide), about 12 to 14°F across Northern Virginia. On nights near that, running almost nonstop is what it was sized to do. Here’s how heat pumps handle a Virginia winter.

A new heat pump outdoor unit with an insulated line set and filter drier on a paver patio at a Northern Virginia home
A new outdoor unit on a patio. On cold days it’s built to run long and steady.

The $67 Heating Check

We check your furnace, heat pump or boiler before winter. Through December 31. See the offer

Book the $67 checkCall (703) 997-9757

Defrost looks like a breakdown

In cold, damp weather, frost builds on the outdoor coil, and the heat pump reverses for a few minutes to melt it. The CEE owner guide says defrost runs about 5 to 15 minutes. You may see steam, hear a whoosh and feel cooler air at the vents while the strips cover. That’s normal. A coil that stays caked in ice is not: heat pump frozen over. Odd sounds are in heat pump making noise.

When it runs constantly for a bad reason

  • Low refrigerant. In NIST lab tests, a heat pump a little more than 30 percent low on refrigerant lost almost 14 percent of its heating capacity and almost 9 percent of its efficiency. A NIST simulation of a house in the Washington climate found a 30 percent undercharge raised yearly energy use 23 percent and stretched backup heat from 89 hours a year to 154.
  • A blocked outdoor coil. The same NIST lab work found a coil 30 percent blocked lost 26 percent of its capacity and 24 percent of its efficiency at the coldest test condition. Leaves, a shrub grown in close or snow piled against it all count.
  • Big setbacks. Turning it down at night and back up in the morning can bring on the strips. The CEE guide says hold it steady and skip changes of 3°F or more.
  • AUX all day. That’s the strips doing the work, and it shows on the bill: AUX heat vs emergency heat and why your electric bill is so high.
  • A code or blinking light. Our error codes and warning lights guide covers the common ones.
A new outdoor unit on a pad beside a brick Northern Virginia home, with refrigerant gauges and tanks set up for the charge
Gauges on for the charge. NIST found a heat pump a little over 30 percent low on refrigerant gives almost 14 percent less heat.

Is it the heat pump or the house?

If the heat pump checks out and still can’t keep up, look at where the heat goes: leaky ducts, one cold room, or a system that was never sized for the house. When the outdoor unit itself is the problem, that’s heat pump repair.

What we check

Our heating check is $67 per system, through December 31: furnace, heat pump or boiler. On a heat pump we look at the outdoor coil, check how it heats and watch when the backup strips come on and why. Tell us if AUX stays on when you book.

Holding a quote already? Our free second opinion sends a tech to look at the system you were quoted on and tell you what it actually needs, with our price if you want it. You don’t owe us anything for looking.

Book it

Book the heating check, call (703) 997-9757, or book online from goswiftpro.com/cookiesoffer and a box of warm cookies comes with the visit. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.

Questions people ask

Is it normal for a heat pump to run constantly in winter?

On cold days, yes. Near freezing and colder, a heat pump runs long and steady, and near the design temperature, about 12 to 14°F in Northern Virginia, it may barely stop. Nonstop on a mild day is not normal.

At what temperature does a heat pump need backup heat?

An older single-stage heat pump usually starts needing help around 30°F, its balance point. Cold-climate models are built to keep heating at much lower temperatures.

Why is my heat pump running but the house isn’t warm?

Low refrigerant, a blocked outdoor coil, leaky ducts or a defrost problem are common causes. If AUX is on all day, the backup strips are carrying the house, and that shows up on the electric bill.

Should I turn my heat pump down at night?

Usually no. Turning it back up in the morning can bring on the backup strips. Hold it steady and save setbacks for trips longer than a day.