We took 40 readings across a range of domestic heat pump installs in 2025. The median reading at 1m was 42dB — roughly the sound of a library. The outliers were mostly siting mistakes, not bad hardware.
The readings
42dB is the median at 1 metre. By 3 metres, most units drop to 33–36dB — quieter than a fridge. The loudest reading in the set (58dB) was a unit mounted directly against a brick wall with zero acoustic matting; the quietest (37dB) had a simple rubber mounting plate.
What actually changes noise
- Vibration coupling: rubber mounts matter more than the unit brand.
- Reflective surfaces: a unit 30cm from a wall can reflect sound back and amplify it.
- Defrost cycles: briefly louder than normal operation, mostly in winter.