Are heat pumps noisy? What to expect
What a heat pump sounds like, and the noise check your installer must pass before one goes in.
The short answer
No, not when it’s sited and installed properly. Most heat pumps produce noise levels similar to a gas boiler, and before one goes in, your installer has to check how loud it will be outside your neighbours’ windows.
It’s the question that stops many people before they ask for a quote: will a unit outside my window drive me mad, and will the neighbours complain? This guide covers what to expect and what to ask your installer.
How loud is a heat pump?
At full power, a modern heat pump is no louder than a gas boiler: about 50 dB(A) at 1 metre. Most of the time it runs well below that, at around 41. Decibels are hard to picture on their own, so here’s how that compares.
Noise Levels Compared
Even at full power, a heat pump is no louder than a gas boiler
Sound fades with distance. Once the noise reaches your neighbours’ window, it must be 37 dB(A) or less, about the same as a library, for the install to go ahead without planning permission. Ground source heat pumps are quieter still, because there’s no outdoor fan and the unit usually sits indoors.
Why heat pumps sound the way they do
It’s a consistent hum because a heat pump works steadily.
The sound comes from the fan drawing air across the outdoor unit, and from the compressor. A boiler fires in short bursts, usually in an indoor cupboard. A heat pump runs for long stretches at a lower level, outside. As with any new sound, you may notice it at first, even if it’s no louder than the boiler it replaced.
On cold days, ice can build up on the outdoor unit. When it does, the sound rises a little as it ices up, pauses while it defrosts, then starts again at its usual level.
The way you run your heat pump is also important. If you switch it off and on like a boiler, it has to work harder to catch up, which makes more noise. Left to run consistently, it makes less noise and uses less energy. Many models also have a night mode that turns the noise down at set hours.
The rules that keep a heat pump quiet
Before a heat pump goes in, your installer has to prove it will meet the noise limit at your neighbours’ windows.
Most heat pumps go in without planning permission. In England and Wales, that’s only allowed if the installer completes a noise calculation called MCS 020 a), which is set by MCS, the body that certifies heat pump installations. If any check point comes out above 37 dB(A), that position doesn’t qualify. The installer will look for a different spot or a quieter unit; if neither works, you’ll need planning permission.
How the Noise Check Works
Your installer checks the noise at every window that counts
In this example, the fence hides the living room window, which takes 10 dB off that check point. It doesn't hide the bedroom window above it.
Every check point must come out at 37 dB(A) or below
- Each check point sits 1 metre outside a window or door of a room your neighbours live or sleep in.
- A solid wall or fence lowers the figure only for the windows it hides from the unit.
- Hedges and gappy fences count for nothing.
- Bathrooms, hallways and utility rooms don't count.
The installer must use the unit’s normal noise figure, not its night mode, and complete the calculation for your property before any work starts. They must also give you a copy.
What the research says
Neighbours rarely notice heat pumps, and hardly anyone complains.
Complaints are rare. 124 of the 242 councils that answered a Freedom of Information request had no heat pump noise complaints on record. Councils note that passing the noise check doesn’t rule out a complaint, so placement matters.
A street of them isn’t much louder than one. Research in 2024 for Nesta found no significant increase in noise from several heat pumps in one neighbourhood.
The calculation errs on the side of caution. In a 2026 University of Salford study, real heat pumps came out about 2 dB below what the calculation predicted. It was only one site, so it’s an early result.
What Neighbours Hear
Dogs bother people far more than heat pumps do
Sounds people living near a heat pump notice from indoors during the day
Where you put it matters
The same heat pump can sound different depending on where it sits.
Distance makes the biggest difference. Every time you double the distance to a window, the noise drops by about 6 dB. Moving a few metres further from a bedroom window, yours or a neighbour’s, is worth it.
When you talk it through with your installer:
Avoid tight corners. Walls close to the unit bounce the sound back. A unit boxed in on every side, like in a small lightwell, can’t pass the noise check.
Use a solid wall or fence. It must be brick, or a fence at least 18mm thick with no gaps. It takes 10 dB off if it hides the unit completely from the window, and 5 dB if it hides part of it.
Ask for anti-vibration feet, so the hum doesn’t travel through the ground into the house.
Tell your neighbours before the install.
The noise check covers your neighbours’ windows, not yours. Your installer will also help you keep the unit away from your bedroom, and talk you through where it goes before you agree to anything.
Is my heat pump’s noise normal?
Most sounds are the unit doing its job. A few are worth a call.
Normal
- A steady hum while your home stays warm and there are no error codes
- A rise in sound as ice builds on a cold day
- A pause while it defrosts, then the hum starts again
Call your installer
- Knocking
- Grinding
- A high-pitched squeal
- A rattle
Take a short video and note the date it started, so they can find the cause.
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Questions people ask
Are heat pumps noisier than boilers?
About the same. At full power, and lower the rest of the time. A heat pump runs steadily for longer at a lower level, whereas a boiler fires in short bursts.
How close can a heat pump be to a neighbour’s window?
There’s no fixed distance. In England and Wales, to avoid needing planning permission, it must be 37 dB(A) or below, 1 metre outside each window or door of the rooms your neighbours live and sleep in. Your installer calculates this for your site.
Can I have a heat pump with a small garden?
Often, yes. It depends on finding a spot that passes the noise check, not on your garden’s size. Where no spot works, you can apply for planning permission.
Do heat pumps get louder in winter?
They can sound different. The sound rises a little as the unit ices up on a cold night, then drops again once it has defrosted.
What’s the difference between sound power and sound pressure?
You’ll see both on spec sheets. Sound power is the total noise the unit emits, regardless of where you stand. Sound pressure is what you hear at a given spot, and it drops off as you move farther away. When you compare models, check which figure you’re looking at and how far away it was measured.
When did the noise rules change?
England made the MCS noise calculation the only route on 29 May 2025, under S.I. 2025/560. Installs already allowed under the old rules could still go ahead until 28 May 2026. Wales followed on 1 June 2026. Scotland and Northern Ireland have their own rules.
Are there other limits without planning permission?
Yes. On a house, the outdoor unit can be no bigger than 1.5 cubic metres, and it can’t go on a pitched roof (Planning Portal).
What should I ask an installer about noise?
Where they plan to put the unit and why, whether the model is Quiet Mark certified, and for a copy of the noise calculation. They must give you one.
Sources
Nesta, Are heat pumps noisy and is there regulation on noise?
Department for Energy Security and Net Zero, Air source heat pump planning regulations review: technical annex, 2023
Hive, Air source heat pump noise levels
MCS, MCS 020 a) Air source heat pump sound calculation, Issue 1.1, April 2025
Hargreaves et al., University of Salford for the Heat Pump Association, Field assessment of air source heat pump noise levels and propagation in a UK housing development: initial report, March 2026
Nesta, What homeowners want to know about heat pumps: data-driven FAQs
Saga, Freedom of Information request to UK councils
Rossendale Borough Council, Noise from air source heat pumps
Apex Acoustics for Nesta, Air source heat pump cumulative noise impact, July 2024
Nesta, Heat pumps: a user survey, May 2023
S.I. 2025/560
MCS, Changes to permitted development rights in Wales from 1 June 2026
Planning Portal, Air source heat pumps: planning permission
Vaillant, aroTHERM plus installer’s quick guide, March 2024
Heat Pumping Technologies, Effect of heat sinks and operation modes on acoustic emissions, webinar, November 2020
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