HeatPumpHeat Pump Noise Levels: How Loud Are They Really?
Noise is one of the top concerns people have about air source heat pumps — especially in terraced houses or dense urban areas. The good news: modern heat pumps are far quieter than most people expect. Here are the actual numbers.
Decibel Levels: What to Expect
A modern air source heat pump produces 42–55 dB at 1 metre from the unit. Sound drops by roughly 6 dB each time you double the distance, so at 3 metres it's around 36–49 dB, and at 5 metres it's 32–45 dB.
To put that in context, here's how heat pump noise compares to everyday sounds:
| Sound Source | Decibels (dB) | Comparison |
|---|---|---|
| Rustling leaves | 20 dB | — |
| Quiet bedroom at night | 30 dB | — |
| Fridge humming | 40 dB | Similar to quiet HP at 3m |
| Heat pump at 3m | 36–49 dB | Typical distance to boundary |
| Heat pump at 1m | 42–55 dB | Right next to the unit |
| Quiet conversation | 50 dB | — |
| Gas boiler (running) | 50–60 dB | Louder than most HPs |
| Normal conversation | 60 dB | — |
| Washing machine (spin) | 70 dB | — |
| Lawnmower | 90 dB | — |
Planning Rules and MCS 020
Air source heat pumps are permitted development in most cases, meaning you don't need planning permission. However, there's a noise condition: the heat pump must not cause noise that exceeds 42 dB at the nearest neighbouring property's habitable room window.
MCS-certified installers are required to carry out a noise assessment using the MCS 020 standard before installation. This calculation considers:
- The sound power level of the specific heat pump model
- Distance to the nearest neighbour's windows
- Reflective surfaces (walls, fences) that can amplify sound
- Whether the unit is in a corner (which adds up to 9 dB)
If the assessment shows noise would exceed limits, the installer must either choose a quieter model, reposition the unit, or add acoustic mitigation.
Positioning Tips to Reduce Noise
- Avoid corners: Placing the unit in a corner between two walls can add 6–9 dB. An open position against a single wall is better.
- Face away from neighbours: The fan (loudest part) should face your garden, not the boundary.
- Distance from boundaries: Permitted development requires at least 1 metre. More distance is always better — 3 metres reduces noise significantly.
- Away from bedrooms: Position the unit away from bedroom windows (yours and your neighbours').
- Anti-vibration mounts: Rubber feet or anti-vibration pads prevent low-frequency hum from transferring through walls or paving. Cost: £20–£50.
- Acoustic enclosures: Purpose-built enclosures can reduce noise by 5–10 dB. Cost: £200–£500. Ensure adequate airflow — the unit needs unobstructed air circulation.
Night Mode and Variable Speed
Most modern heat pumps feature inverter-driven compressors that adjust speed based on demand. On a mild autumn evening, the compressor runs slowly and quietly (35–40 dB). It only ramps up to full speed — and full noise — during the coldest winter days.
Many models also have a dedicated quiet/night mode that caps the fan speed and compressor output. This reduces noise by 3–8 dB at the cost of slightly reduced heating output. For most homes, the overnight heat demand is lower anyway, so this trade-off is barely noticeable.
Terraced Houses and Urban Properties
If you live in a terraced house with limited space between your property and neighbours, noise needs more careful planning. Options include:
- Choosing a premium low-noise model (some achieve 42 dB at 1m)
- Front or rear garden positioning where distance to neighbours is greatest
- Acoustic barriers or fencing between the unit and the boundary
- Considering a ground source heat pump if noise is a deal-breaker — they're virtually silent
The Reality
The vast majority of heat pump owners report that noise is a non-issue. Once you're inside the house with doors and windows closed, the heat pump is inaudible. Outside, it's comparable to a fridge or the background hum of a quiet street. It's one of those things that worries people before installation but is rarely mentioned afterwards.
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Frequently Asked Questions
How loud is an air source heat pump?
Modern air source heat pumps produce 42–55 dB at 1 metre. At 3 metres (typical distance to a boundary), this drops to around 36–49 dB. For comparison, a fridge is about 40 dB and a normal conversation is 60 dB. Most people find them inaudible from inside the house.
Can neighbours complain about heat pump noise?
They can, but it is rarely a legitimate issue with modern units. Permitted development rules require that noise at the nearest neighbouring window does not exceed 42 dB. MCS installers must complete a noise assessment (MCS 020) before installation to ensure compliance.
Are heat pumps noisy at night?
Most heat pumps have a quiet or night mode that reduces fan speed and output, dropping noise to 35–40 dB — quieter than a bedroom at night. Some models also have scheduling features to avoid running during antisocial hours.
Where should I put the outdoor unit to reduce noise?
Position the unit away from bedroom windows (yours and neighbours). Avoid corners between walls, which amplify sound. A distance of at least 1 metre from boundaries is required, and 3+ metres is ideal. Anti-vibration mounts and acoustic enclosures can further reduce noise.
Is a ground source heat pump quieter?
Yes. Ground source heat pumps are virtually silent because the compressor is housed indoors and the ground loops produce no noise. If noise is a serious concern — for example, in a terraced house with close neighbours — GSHP eliminates the issue entirely.