The Quick Answer
A modern air source heat pump produces around 40–50 decibels measured at one metre from the unit. At the distance of a typical neighbour’s window — 3 to 5 metres — the noise drops to approximately 30–38 decibels, equivalent to a whisper or the hum of a quiet bedroom at night. This is below the 42 dB(A) permitted development limit measured at the nearest neighbouring habitable room window. In practice, neighbour complaints about heat pump noise are extremely rare when units are correctly positioned (Energy Saving Trust).
Related reading: Do I need planning permission for a heat pump? | Best heat pump brands UK 2026
Real Noise Levels: What the Data Shows
Heat pump noise levels are measured in decibels (dB) and stated at specific distances. Manufacturers publish noise data measured at one metre from the unit, but this does not reflect what the unit sounds like from where people actually are.
Here are typical noise levels for modern domestic air source heat pumps at different distances:
| Distance from Unit | Typical Noise Level | Comparable Sound |
|---|---|---|
| At the unit (0.5m) | 48–55 dB | Quiet office conversation |
| 1 metre | 42–50 dB | Refrigerator running |
| 3 metres | 33–41 dB | Quiet library |
| 5 metres | 28–36 dB | Whisper |
| 10 metres | 22–30 dB | Rustling leaves |
Sound drops by approximately 6 decibels every time you double the distance from the source. This works heavily in favour of heat pump installations — a modest distance of 3–5 metres between the unit and a neighbour’s window reduces noise dramatically.
How decibels work
The decibel scale is logarithmic, which means a small change in dB represents a significant change in perceived loudness:
- 3 dB increase = sound energy doubles (barely noticeable to the human ear)
- 10 dB increase = sounds twice as loud to the human ear
- 20 dB increase = sounds four times as loud
This means the difference between 42 dB (the planning limit) and 52 dB (an older, noisier unit) sounds roughly twice as loud — which is why modern, quieter units matter.
Decibel Comparison Table: Everyday Sounds vs a Heat Pump
| Sound | Typical Decibel Level |
|---|---|
| Breathing | 10 dB |
| Rustling leaves | 20 dB |
| Whisper at 1 metre | 30 dB |
| Quiet bedroom at night | 30–35 dB |
| Heat pump at 5 metres | 28–36 dB |
| Quiet library | 35–40 dB |
| Refrigerator humming | 35–40 dB |
| Heat pump at 1 metre | 42–50 dB |
| Quiet conversation | 40–45 dB |
| Rainfall | 45–50 dB |
| Dishwasher | 45–55 dB |
| Gas boiler flue | 40–50 dB |
| Normal conversation | 55–65 dB |
| Washing machine (spin cycle) | 70–75 dB |
| Vacuum cleaner | 70–80 dB |
| Lawn mower | 85–90 dB |
A heat pump at a typical neighbour-facing distance (3–5 metres) sits at the same level as a quiet bedroom — well below everyday sounds like rainfall, a dishwasher, or a conversation.
The 42 dB Planning Rule Explained
Under UK permitted development rules, an air source heat pump can be installed without planning permission provided it meets the MCS 020 noise condition:
The heat pump must not exceed 42 dB(A) at the nearest neighbouring property’s habitable room window or door.
What does 42 dB sound like?
42 dB is roughly the sound of a quiet library or a refrigerator humming. It is well below the level of a normal conversation (55–65 dB) and similar to the ambient background noise of a quiet residential street during the day.
How is the 42 dB limit checked?
Installers use the manufacturer’s published noise data along with the distance to the nearest neighbour’s window to calculate whether the installation will comply. The calculation follows a simple formula: for every doubling of distance, the noise drops by 6 dB. So if a heat pump produces 48 dB at 1 metre:
- At 2 metres: 42 dB
- At 4 metres: 36 dB
- At 8 metres: 30 dB
A heat pump rated at 48 dB at 1 metre needs just 2 metres of distance from the nearest neighbour’s window to comply. Most installations comfortably exceed this.
What if you cannot meet the 42 dB limit?
- Choose a quieter unit — many modern heat pumps are rated at 42–45 dB at 1 metre, making compliance easy even at short distances
- Reposition the unit — moving the heat pump further from the boundary or to a different wall
- Install acoustic shielding — a purpose-built acoustic enclosure or barrier can reduce noise by 5–10 dB
- Apply for planning permission — if none of the above is feasible, planning permission may be granted even where the permitted development noise limit cannot be met
Quietest Heat Pump Brands in 2026
| Brand and Model | Noise Level at 1m | Noise Level at 3m (est.) | Notes |
|---|---|---|---|
| Vaillant aroTHERM plus | 42 dB | 33 dB | One of the quietest on the market |
| Samsung EHS Mono HT Quiet | 43 dB | 34 dB | Dedicated quiet mode available |
| Daikin Altherma 3 | 44 dB | 35 dB | Variable speed compressor |
| Mitsubishi Ecodan R290 | 45 dB | 36 dB | Proven reliability |
| Grant Aerona3 R32 | 46 dB | 37 dB | Popular in rural installations |
| Bosch Compress 7001iAW | 44 dB | 35 dB | Quiet operation, compact design |
The trend in the industry is firmly towards quieter operation. Manufacturers have invested heavily in sound reduction, driven by the 42 dB permitted development requirement and homeowner demand.
What makes some heat pumps quieter than others?
- Inverter-driven compressors — adjust speed continuously rather than running at full blast
- Low-speed fan designs — larger fans running at lower speeds move the same volume of air more quietly
- Acoustic insulation — sound-absorbing material inside the unit casing
- Vibration dampening — rubber mounts prevent vibration from transferring to the ground or wall
- Night mode — many units limit compressor and fan speed overnight, reducing noise by 3–5 dB
How to Minimise Heat Pump Noise
Positioning
- Avoid placing the unit directly below a bedroom window — yours or your neighbour’s
- Avoid enclosed corners — sound can bounce off two adjacent walls (the “corner effect”), amplifying perceived noise by 3–6 dB
- Mount on a solid, level concrete base — this prevents vibration and rattle
- Maintain clear airflow — do not obstruct the fan outlet
Anti-vibration mounts
Rubber anti-vibration pads between the heat pump and its concrete base prevent vibration from transferring through the ground. These cost under £50 and make a noticeable difference, particularly for units mounted close to the house.
Acoustic barriers
If the unit needs to be close to a neighbour’s boundary, a purpose-built acoustic fence or barrier can reduce noise transmission by 5–10 dB. Important: never fully enclose a heat pump. The outdoor unit needs free airflow to work properly. Any acoustic barrier must maintain at least 300mm clearance on all sides and not obstruct the fan outlet.
Night mode
Most modern heat pumps have a night mode that can be scheduled to run during sleeping hours (typically 10pm to 7am). Night mode reduces compressor and fan speed, dropping noise levels by 3–5 dB. Since heat demand is typically lower at night anyway, this rarely affects comfort.
What About Neighbour Complaints?
The legal position
There is no law that prevents you from installing a heat pump, provided it meets permitted development conditions (including the 42 dB noise limit). If your installation complies, a neighbour cannot object on noise grounds through planning.
Practical advice
- Talk to your neighbours before installation — most concerns come from unfamiliarity, not genuine noise issues
- Invite them to hear a working unit — a quick listen eliminates most worries
- Consider their bedroom and living room windows — position the unit away from the rooms where they spend the most time
- Keep good records — your installer should provide the noise calculation showing compliance with the 42 dB limit
What the evidence shows
The Energy Saving Trust and Nesta’s Electrification of Heat project surveyed thousands of heat pump owners and their neighbours. The findings were clear: the vast majority of neighbours reported no noise disturbance from a heat pump. Where issues did arise, they were almost always resolved by repositioning the unit, adding acoustic shielding, or activating night mode.
What Does a Heat Pump Actually Sound Like?
A modern air source heat pump produces a low, constant hum — similar to a large refrigerator or a distant car engine at idle. It is not a sharp, sudden, or irregular sound. There are no bangs, clanks, or high-pitched whines.
The sound character matters: research shows that constant, low-frequency sounds are much less annoying than intermittent or tonal sounds at the same volume. A heat pump running at 40 dB is far less noticeable than a dog barking at 40 dB or a dripping tap at 30 dB.
Indoor Noise
The outdoor unit is not the only potential noise source. The indoor unit and the hot water cylinder are also part of the system.
- Indoor unit: Produces a very quiet hum from the circulation pump, typically around 30–35 dB — similar to a fridge in the same room. It is usually installed in a utility area, airing cupboard, or garage, so it is rarely noticed.
- Hot water cylinder: Virtually silent.
- Pipework: Occasionally, you might hear a gentle gurgle of water in the pipes when the system is heating up or cooling down. This is normal and no different from any central heating system.
Overall, the indoor components of a heat pump are no louder than a conventional boiler installation.
How Electromatic Can Help
Electromatic M&E Ltd offers free home surveys across London and Surrey (TW, KT, SW postcodes). We handle BUS Grant applications (subject to eligibility), install ASHP and solar PV from a single contractor, and deliver within 2–4 weeks of survey confirmation. All work is carried out under MCS certification via our accredited umbrella partner. Where noise is a concern — particularly for close neighbours — we carry out a site-specific noise calculation before installation and advise on the best unit position and any acoustic measures needed.
Call us: 07718 059 284 | Email: admin@electromatic.uk
Frequently Asked Questions
How many decibels is a heat pump?
A typical modern air source heat pump produces 42–50 decibels at 1 metre from the unit. At a distance of 3–5 metres (the typical distance to a neighbour’s window), this drops to around 30–38 decibels — roughly the volume of a whisper or a quiet bedroom. This is quieter than a dishwasher, a washing machine, or a normal conversation.
Can you hear a heat pump from inside the house?
In most cases, no. With the outdoor unit positioned on an external wall and the windows closed, the heat pump is virtually inaudible from inside the home. With windows open, you may hear a faint hum similar to a distant fridge. The indoor components produce around 30–35 dB — similar to a boiler or fridge in the same room.
Will a heat pump annoy my neighbours?
In the vast majority of cases, no. Modern heat pumps are designed to meet the 42 dB permitted development noise limit at the nearest neighbour’s window. At this level, the sound is equivalent to a quiet library — well below the background noise of a typical residential area. Studies by the Energy Saving Trust show that neighbour complaints about heat pump noise are extremely rare.
What is the permitted development noise limit for a heat pump?
Under UK permitted development rules, an air source heat pump must not produce more than 42 dB(A) measured at 1 metre from the nearest neighbour’s habitable room window or door. If this limit cannot be met through positioning alone, options include choosing a quieter unit, adding acoustic shielding, or applying for full planning permission.
Are heat pumps noisier in winter?
A heat pump works harder in cold weather, so the compressor and fan run at higher speeds, producing slightly more noise. The difference is typically 3–5 dB more than in mild conditions. Even at maximum output on the coldest winter days, a well-chosen modern unit will remain within the 42 dB limit at a neighbour’s window. Night mode can be used to reduce noise further during sleeping hours.
The information in this article is for general guidance only and does not constitute financial, legal, or technical advice. Noise data is based on manufacturer specifications and standard acoustic principles. Actual noise levels depend on the specific heat pump model, site conditions, and installation positioning. Planning rules are subject to change — verify current permitted development conditions with your local planning authority. The Boiler Upgrade Scheme (BUS) grant of £7,500 is subject to eligibility criteria set by Ofgem — not all properties qualify. Electromatic M&E Ltd operates under MCS certification via our accredited umbrella partner. All installations comply with Building Regulations Part L and MCS standards. E&OE.
Written by Electromatic M&E Ltd — ASHP & Solar installer, London & Surrey (electromatic.uk)
Last updated: April 2026 | Electromatic M&E Ltd, Company No. 13837345
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