Heat pumps

Heat pump noisy at night

Warning Do not attempt any electrical or gas work yourself. Always use a qualified, MCS-certified, or Gas Safe registered professional for repairs.

What you’re seeing (symptoms)

You may notice a humming, buzzing, or whirring sound coming from the outdoor unit of your heat pump, which seems more noticeable during the night or early morning hours.

What’s normal vs not normal

Normal:

  • A steady humming or whirring sound when the fan and compressor are running.
  • A slight increase in noise during very cold weather when the unit works harder.
  • Occasional “wooshing” sounds during a defrost cycle.

Not normal:

  • Loud banging, clattering, or metal-on-metal scraping sounds.
  • Excessive vibration that can be felt inside the house.
  • Rattling that suggests loose panels or debris.

Likely causes (ranked)

  1. Lower background noise: Everything seems louder at night when the neighborhood is quiet.
  2. Defrost mode: On cold nights, the unit enters defrost mode, which changes the sound profile.
  3. Vibration transfer: The unit may not be properly decoupled from the ground or wall.
  4. Loose components: Panels or screws may have loosened over time.
  5. Debris: Leaves or twigs caught in the fan housing.

Quick checks you can do safely

  • Check for any visible debris like leaves or twigs in the fan area (ensure the unit is off before looking closely).
  • Ensure all external panels appear secure and not vibrating against each other.
  • Verify the unit is sitting level on its base.

When to call an installer

  • If the noise has significantly changed recently.
  • If you hear grinding or loud mechanical banging.
  • If the unit is vibrating excessively and transferring noise through the walls.

Questions to ask your installer

  • “Can you check if the anti-vibration mounts are still effective?”
  • “Is the unit’s ‘quiet mode’ or ‘night mode’ enabled in the settings?”
  • “Are there any loose internal components causing the rattle?”

Related NetZeroNow tools & guides

FAQs

Is it normal for a heat pump to be louder in winter? Yes, as the temperature drops, the heat pump has to work harder and may enter defrost cycles more frequently, both of which increase noise slightly.

What is ‘Night Mode’? Many modern heat pumps have a setting to reduce fan and compressor speed at night to lower noise levels, though this may slightly reduce heating capacity.

Can I build a fence around it to block the noise? You must ensure any screening allows for adequate airflow. Consult your installer before blocking the unit’s intake or exhaust.

Does a noisy heat pump mean it’s broken? Not necessarily. Most “noise” complaints are due to installation resonance or simply the quietness of the night environment.

Should I turn it off at night to save noise? No, heat pumps are designed to run continuously. Turning it off can lead to the house cooling down too much, making the unit work even harder (and louder) in the morning.

Written by NetZeroNow | Last updated on 2026-03-02