Vent, Valve & Volt
Heat pump not heating, or blowing cool air

This is normal

Probably normal: deep cold reduces output

Carrier says heat pumps naturally lose some efficiency as temperatures drop below freezing. Mildly warm air on a bitter day may be normal.

Why this happens

A heat pump moves heat from the outdoor air into your house, and there's less to collect when it's very cold. Carrier notes the efficiency drop below freezing and says emergency heat may be used sparingly, since it raises bills. Energy.gov notes that cold-climate heat pumps are designed to perform in temperatures as low as 5F, so how much your system slows depends on its design.

What to do

  1. Leave the thermostat on Heat and give the system time; it may run longer on cold days.
  2. Keep the outdoor unit clear of snow and debris, switching off the outdoor disconnect before you clear it by hand.
  3. If the house can't keep up, Carrier says emergency heat may be used sparingly. Switch back to Heat when it warms up.
  4. If it also struggles on milder days, call an HVAC technician.

If it still worries you, tell the HVAC technician

  • The outdoor temperature when it struggled.
  • Whether it keeps up on milder days.
  • Whether you used emergency heat and how often.
  • The heat pump brand, model and age from the outdoor unit's data plate.

Build the full list: what to tell the HVAC technician.

Start this troubleshooter over

References (every fact above comes from one of these pages)
  1. Carrier: Heat pump not heating
  2. Energy.gov Energy Saver: Heat pump systems

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