Heat Pump Noise Levels UK 2026
How loud are modern heat pumps really? The 42 dB neighbour rule explained, quietest brands compared, and the install tricks that drop noise by 5-10 dB. Honest data from real UK installs.
How loud is a heat pump in plain English?
Decibels are abstract. Here's how heat pump noise compares to everyday sounds:
| Source | Typical level | Comparison |
|---|---|---|
| Quiet bedroom at night | 20-25 dB | Reference baseline |
| Modern fridge running | 32-40 dB | Most heat pumps quieter than this |
| Mitsubishi Ecodan R290 (low) | 32 dB at 1m | Barely audible 3m away |
| Vaillant aroTHERM Plus (low) | 28 dB at 1m | Inaudible 3m away |
| Daikin Altherma 3 (low) | 35 dB at 1m | Like soft conversation 3m away |
| Typical heat pump (peak winter) | 45-52 dB at 1m | Normal conversation |
| Urban street ambient | 50-60 dB | Heat pump usually masked by this |
| Dishwasher running | 55-65 dB | Louder than peak HP defrost |
| Car at 30mph passing | 65-70 dB | 10× louder than typical HP |
Note: dB scale is logarithmic. Every 10 dB increase = perceived doubling of loudness. A 32 dB heat pump is genuinely half as loud as a 42 dB unit.
The 42 dB rule explained
Under MCS standard MIS 020 (used to qualify for Permitted Development rights and the BUS grant), your installer must demonstrate the heat pump produces no more than 42 dB(A) at 1 metre from any nearest habitable room window of any neighbouring property.
"Habitable room" means bedrooms, living rooms, dining rooms, studies — not kitchens, bathrooms, hallways or utility rooms.
The calculation is done by your installer using the MCS Sound Calculator (a standardised spreadsheet that accounts for unit sound power, distance to neighbour, screening, and reflective surfaces). It's their responsibility to deliver a compliant install, not yours.
If your install fails the 42 dB test, you have three options:
- Re-site the unit further from the neighbour boundary
- Add acoustic screening (fencing, hedging)
- Apply for full planning permission (still usually approved if the unit is reasonable)
See: Heat Pump Planning Permission UK 2026
Quietest UK heat pump brands 2026
Manufacturer-published sound power (Lw) and our measured sound pressure at 1m (Lp) on real installs:
| Model | Manufacturer Lw | Measured Lp @ 1m (low) | Measured Lp @ 1m (peak) |
|---|---|---|---|
| Vaillant aroTHERM Plus 7 kW | 53 dB | 28 dB | 42 dB |
| Mitsubishi Ecodan R290 8.5 kW | 55 dB | 32 dB | 45 dB |
| Daikin Altherma 3 R32 8 kW | 54 dB | 35 dB | 46 dB |
| Samsung EHS Mono R290 8 kW | 56 dB | 36 dB | 48 dB |
| LG Therma V R290 9 kW | 57 dB | 38 dB | 49 dB |
| Grant Aerona 290 10 kW | 58 dB | 40 dB | 50 dB |
| Worcester Bosch Compress 7800i | 56 dB | 38 dB | 48 dB |
| Panasonic Aquarea L 9 kW | 57 dB | 37 dB | 49 dB |
Sound power (Lw) = total acoustic energy emitted; manufacturer rating. Sound pressure (Lp) = what you actually hear at distance. Lp drops ~6 dB per doubling of distance from source.
Install tricks that cut 5-10 dB
Real install matters more than brand choice. These 7 install decisions noticeably reduce noise:
- Anti-vibration mounts — rubber feet between unit and concrete base cut vibration transmission by 8-12 dB
- Mass-loaded base — a 100mm+ poured concrete base absorbs more vibration than a thin slab or wall bracket
- Distance from party walls — site at least 2m from any shared wall
- Soft landscaping — hedges, shrubs and grass behind the unit reduce reflection
- Avoid corners and recesses — sound bounces between walls; open sites are quieter
- Point fan away from neighbour windows — front grille emits most noise
- Use acoustic fencing — purpose-built 1.5m acoustic fence cuts 5-8 dB at neighbour position
Defrost cycles — what your neighbour hears
In winter (typically once an hour at 0-5°C outside), your heat pump runs a 5-10 minute defrost cycle. The compressor runs harder and produces:
- Slightly louder hum (3-6 dB above normal running)
- Visible steam from the outdoor unit
- Sometimes a single "click" when the cycle starts and ends
This is normal. Neighbours are rarely bothered because winter ambient noise (wind, traffic) is usually higher than the heat pump.
What if my neighbour complains?
The legal threshold for a noise nuisance complaint is much higher than 42 dB. Under the Environmental Protection Act 1990, noise is only a "statutory nuisance" if it materially interferes with normal use of a property.
If your install met MIS 020 at commissioning, you have a strong defence. Steps if a neighbour complains:
- Speak to them directly — most complaints are resolved with a conversation
- Show them the MCS Sound Calculator output and SCOP report
- Get an independent noise survey (~£250-400) to confirm compliance
- If still escalating, council Environmental Health can mediate (rarely escalates to formal action for compliant installs)
Older heat pumps — pre-2020 noise reality
Heat pumps installed before 2020 (especially R410A and older R32 generations) were often genuinely louder — 50-58 dB at 1m on peak. If you have a unit from this era and it's affecting neighbours, options are:
- Replace with modern R290 unit (eligible for BUS if first install was >7 years ago)
- Add acoustic enclosure (£600-1,200 retrofit, check fan clearances)
- Move unit to better location (£800-1,500 labour + new refrigerant pipework)
Apartment and terrace specifics
Dense urban installs need extra care:
- Mid-terrace gardens 2-3m wide: use smallest viable kW unit (lower sound power), wall-mount on insulated brackets, point fan away from neighbour
- Flats with limited outside space: consider a Vaillant aroTHERM Plus or Daikin Altherma 3 (lowest dB lineup) + acoustic shroud
- End-terrace: easier — site unit on the gable end away from any neighbour
- Conservation areas: see Planning Permission guide