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Are heat pumps noisy? The 37 dB(A) answer, in plain terms

Not especially: a modern air source heat pump runs at roughly 30 to 38 dB(A) depending on the model and mode, and England's planning system backs that up with a hard sound limit rather than a distance rule. Here is what the number means and what else permitted development requires.

Updated 4 August 2026 · written by the Clearline guidance team

8 dated sources, listed in full below Independent guidance, written to inform rather than sell Figures recomputed at every update, never recycled

An air source heat pump outdoor unit mounted at a UK terraced house

The short answer

Not especially. A modern air source heat pump runs at roughly 30 to 38 dB(A) depending on the model and mode, and most installations in England go in under permitted development, which means no planning application. That permission rests on one calculation and a short list of physical conditions. The calculation is MCS 020 (a), the sound calculation for permitted development installations, and it has to return 37.0 dB(A) or lower at the assessment position.

The 1 metre boundary rule is gone

Class G used to bar a unit within 1 metre of the property boundary. The amendment order that came into force on 29 May 2025 removed it. A unit can now sit against a neighbour's fence in England provided the sound calculation passes. The only 1 metre rule left is on flat roofs, where every part of the unit must be at least 1 metre from the external edge.

The 37 dB(A) sound test

Class G permits a heat pump only if the installation complies with the MCS Planning Standards, and for air source units that means MCS 020 (a). The pass mark is 37.0 dB(A) or lower at the assessment position, which sits at the nearest noise sensitive premises rather than at your own house. Meet it and the installation is permitted development, subject to the other conditions below. Miss it and you are applying for planning permission.

Manufacturer noise figures are a useful first filter but they are not the test. They are quoted at a stated distance and in a stated operating mode. Vaillant quotes below 30 dB(A) at 3 metres for the aroTHERM plus. Daikin quotes 38 dB(A) at 3 metres for the Altherma 3 H HT, and 35 dB(A) in low sound mode. Samsung quotes 35 dB(A) in quiet mode on the EHS Mono R290. None of those numbers predicts what the calculation returns at a neighbour's window, because that depends on where the unit ends up.

The standards route hardened in May 2026

The 2025 amendment order struck the words 'or equivalent standards' out of the noise condition and gave a transitional window running to 28 May 2026. That window has closed. In England an MCS 020 (a) calculation is now the only accepted way of demonstrating the noise condition under Class G.

The permitted development conditions in England

Condition	What Class G allows	What it means in practice
Sound	MCS 020 (a) must return 37.0 dB(A) or lower at the assessment position	The single test most siting decisions turn on
Boundary distance	No minimum distance from a neighbour's boundary	The old 1 metre rule was removed on 29 May 2025
Number of units	Two on a detached house, one on anything else including flats	A second unit on a semi needs a planning application
Unit volume	1.5 cubic metres on a house, 0.6 cubic metres on a block of flats	Measured on the outdoor compressor unit
Pitched roofs	Not permitted development at all	A pitched roof mount always needs permission
Flat roofs	Every part of the unit at least 1 metre from the external edge	Rules out most small flat roof extensions and dormers
Wind turbines	Not permitted if a turbine is already on the building or in its curtilage	One or the other under Class G, not both
Use	Must not be used solely for cooling	A cooling only installation falls outside Class G

England only, and correct at 4 August 2026. These are the limits. The conditions in the next section apply on top of them.

Where a unit cannot go at all

On a listed building, or on land within its curtilage. That route needs planning permission and listed building consent instead.
On or within the curtilage of a scheduled monument.
In a conservation area or World Heritage Site, on a wall or roof that fronts a highway, or anywhere nearer to a highway bounding the property than the nearest part of the building itself.
Anywhere else, on a wall above the level of the ground floor storey where that wall fronts a highway.
Anywhere at all, if a wind turbine is already installed on the building or inside the curtilage.

Siting is the part homeowners get wrong most often. The free remote design call goes through your actual elevation, boundary and neighbours before anyone quotes, on video, with nothing to sign.

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Siting in practice

Step 1

Start at the neighbour's window, not your wall

The assessment position is at the nearest noise sensitive premises. Two positions that look identical from your own garden can return different results once the distance and direction to that position are counted.

Step 2

Fix the position before the unit is ordered

The calculation is run for one specific unit in one specific position. Change either and it has to be run again, which is a good reason to settle siting at survey stage rather than on installation day.

Step 3

Check what the compliance case relies on

Ask whether the result depends on a quiet or night mode being active, and what that mode does to heat output on the coldest nights of the year. A pass that only holds in quiet mode is worth knowing about early.

Step 4

Get the calculation in writing

Keep the MCS 020 (a) output with your handover pack. It is the evidence that the installation was permitted development, and it is what you will want if a neighbour queries it or when you come to sell.

There is a further condition that is easy to overlook because it is written as a duty rather than a measurement. The unit must be sited, so far as is practicable, to minimise its effect on the external appearance of the building and on the amenity of the area, and it must be removed as soon as reasonably practicable when it is no longer needed. Those apply regardless of how comfortably the sound calculation passes.

Conservation areas, listed buildings and flats

Conservation areas do not rule out heat pumps, they restrict where the unit sits, and the condition is written around highways rather than elevations. The unit must not go on a wall or roof fronting a highway, and it must not sit nearer to a highway bounding the property than the nearest part of the building. On most terraced and semi-detached streets that puts the unit at the back, which is usually where it was going anyway. World Heritage Sites carry the same condition. Listed buildings are a different matter: Class G does not apply, so the installation needs planning permission and listed building consent, both judged on the specific proposal rather than against a fixed limit. Flats are the tightest case of all, with one unit, a 0.6 cubic metre volume limit, and freeholder consent to obtain on top, which is a contractual question separate from planning.

Wales, Scotland and Northern Ireland

Wales made its own amendment order in 2026 and has landed close to England: one unit on a non-detached dwelling or a block of flats, two on a detached house, a 1.5 cubic metre limit on dwellings, and the same removal of 'or equivalent standards' from the MCS Planning Standards condition. One difference worth knowing is the volume limit for blocks of flats, which is 1 cubic metre in Wales against 0.6 in England. Scotland and Northern Ireland run separate permitted development regimes, so treat every figure on this page as an England figure and check the national rules for the property in question.

If your property is listed, in a conservation area, or a flat, settle the planning route before you start comparing quotes. The free design call maps it out and puts you in front of an MCS-certified installation team for your area who have done that version of the job before.

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Planning is one input into a heat pump decision rather than the whole of it. The heat pumps guide covers sizing, flow temperature and running cost, and our coverage map carries a local calculator on every county page. If you are weighing a heat pump against or alongside solar panels, the extra electrical load is worth planning in at the start rather than revisiting it later.

Clearline gives independent guidance and does not install. Installations are carried out by an MCS-certified installation team for your area.

FAQs

Planning questions, answered

Are heat pumps noisy?

Not particularly. Manufacturers quote modern air source heat pumps at roughly 30 to 38 dB(A) at 3 metres depending on the model and mode: Vaillant's aroTHERM plus is below 30 dB(A) at 3 metres, and Daikin's Altherma 3 H HT is 38 dB(A) standard or 35 dB(A) in low sound mode. For permitted development in England, a calculation has to show 37.0 dB(A) or lower at your nearest neighbour's window before installation can go ahead without planning permission.

Do I need planning permission for a heat pump in England?

Usually not. Air source heat pumps on domestic premises fall under Class G permitted development, so no application is needed provided the MCS 020 (a) sound calculation returns 37.0 dB(A) or lower at the assessment position and the installation meets the size, count and siting conditions. Listed buildings, scheduled monuments and pitched roof mounts sit outside Class G and do need permission.

Is there still a 1 metre boundary rule?

No. The condition barring a unit within 1 metre of the property boundary was removed by the amendment order that came into force on 29 May 2025. A unit can now sit adjacent to a neighbour's boundary in England as long as the sound calculation passes. The only remaining 1 metre condition applies on flat roofs, where every part of the unit must be at least 1 metre from the external edge.

How loud is 37 dB(A) in practice?

It is a limit at a position rather than a rating printed on the unit, which is why manufacturer figures and the permitted development test are not interchangeable. Manufacturers quote sound at a stated distance and mode: Vaillant quotes below 30 dB(A) at 3 metres for the aroTHERM plus, Daikin quotes 38 dB(A) at 3 metres for the Altherma 3 H HT and 35 dB(A) in low sound mode. What matters for planning is the calculated figure at the nearest noise sensitive premises.

What happens if the sound calculation does not pass?

You have three options and they are usually tried in that order. Move the unit to a position with more distance from the assessment point, specify a quieter unit, or apply for planning permission and let the local authority decide. A designer who runs the calculation early has room to change the answer; one who runs it on installation day does not.

Can I have a heat pump in a conservation area?

Yes, with a restriction on position. The unit must not be installed on a wall or roof that fronts a highway, and it must not sit nearer to a highway bounding the property than the nearest part of the building. World Heritage Sites carry the same condition. A listed building in a conservation area is a separate case and needs both planning permission and listed building consent.

Can I fit a second heat pump?

On a detached house, yes, two units are within Class G. On a semi, a terrace, or a block of flats the limit is one, so a second unit means a planning application. The volume limit applies per unit: 1.5 cubic metres on a house and 0.6 cubic metres on a block of flats.

Do the England rules apply in Wales and Scotland?

Not automatically. Wales made its own 2026 amendment order which is close to England on unit counts and dwelling volume but sets a 1 cubic metre limit for blocks of flats rather than 0.6. Scotland and Northern Ireland run separate permitted development regimes. Check the rules for the nation the property is in before relying on any figure from an England page.

See the numbers next: Tesla Powerwall 3, installed, or what a battery costs.

Figures and specifications in this guide are sourced below and were checked on the date shown. Rates and product specifications change; we confirm the current picture on your free design call.

Sources

The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2 Part 14 Class G: conditions on unit counts, volume, pitched and flat roofs, conservation areas, World Heritage Sites, listed buildings, scheduled monuments and wind turbines legislation.gov.uk
The Town and Country Planning (General Permitted Development) (England) (Amendment) Order 2025, SI 2025/560, in force 29 May 2025: removal of the boundary condition, revised unit counts and volume limits, removal of 'or equivalent standards', cooling only exclusion, and the transitional provision running to 28 May 2026 legislation.gov.uk
Planning Portal, planning permission guidance for air source heat pumps in England: MCS Planning Standards requirement and the full list of Class G conditions planningportal.co.uk
MCS 020 (a), Air Source Heat Pump Sound Calculation for Permitted Development Installations: the 37.0 dB(A) compliance threshold at the assessment position mcscertified.com
The Town and Country Planning (General Permitted Development) (Amendment) (Wales) Order 2026: Welsh unit counts, dwelling and flats volume limits, and MCS Planning Standards condition legislation.gov.uk
Vaillant aroTHERM plus product information: sound pressure below 30 dB(A) at 3 metres vaillant.co.uk
Daikin Altherma 3 H HT product page and installer brochure: 38 dB(A) at 3 metres standard, 35 dB(A) low sound mode daikin.co.uk
Samsung EHS Mono R290 product page: 35 dB(A) quiet mode samsung-climatesolutions.com