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Heat Pump Noise Limit UK: Is It 37 or 42 dB(A)?

In England and Wales, an air source heat pump installed under permitted development must pass MCS 020 a), which MCS says sets a 37 dB(A) limit. The older 42 dB(A) figure belongs to MCS 020. The number dropped because the calculation changed.

Sumcraft Editorial Team10 min read

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The heat pump noise limit for permitted development in England and Wales is 37 dB(A) under MCS 020 a). The 42 dB(A) figure comes from the older MCS 020.

Checked on 6 November 2026. Updated 7 November 2026 with how far a heat pump can be from a neighbour's window and quiet mode settings by brand. Updated on 6 November with the Wales and Scotland rules and how to complain about a neighbour's heat pump. Everything below comes from legislation.gov.uk and MCS, the scheme that writes the heat pump planning standard. Sources are linked at the end. We could not access the full MCS 020 a) document, so the exact assessment method is not covered here. Ask an MCS certified installer to run the calculation for your home.

WhereStandardSince
EnglandMCS 020 a), 37 dB(A)29 May 2025
WalesMCS 020 a), 37 dB(A)1 June 2026
ScotlandMCS Planning Standards (Class 6H)28 May 2024 guidance
Northern IrelandMCS 020, 42 dB(A)MCS, May 2025

The dB figures come from MCS. The legal requirements come from legislation.gov.uk, gov.wales and gov.scot.

Why you see two different numbers

Most pages quoting 42 dB(A) describe the older standard, MCS 020. MCS's consultation response calls it "the Permitted Development noise limit of 42 dB(A)".

MCS then rewrote the calculation as MCS 020 a). Its consultation response says the new method "creates a corresponding overall limit of 37dB(A)". Two changes explain the lower figure:

  • MCS removed the steps that added an assumed background noise level. Respondents said those steps added burden without value.
  • The new method uses exact distances instead of a rounded table. MCS says its impact assessment found the new method easier to pass.

So 37 dB(A) under the new method is not the same test as 42 dB(A) under the old one. Comparing the two numbers directly is misleading.

What changed in England on 29 May 2025

MCS says the government changed permitted development rights for air source heat pumps in England on 29 May 2025. The changes:

  • Heat pumps can now go within 1 metre of the property boundary.
  • A detached house can have two air source heat pumps instead of one.
  • The size limit for a house rose from 0.6 to 1.5 cubic metres.
  • Air-to-air units used for cooling can now qualify.
  • The installation must comply with MCS 020 a), whether or not the installer is MCS certified.

The permitted development conditions in England

The law is Class G of Part 14 of the General Permitted Development Order 2015. Legislation.gov.uk shows it was amended on 29 May 2025. A heat pump is not permitted development if any of these apply:

ConditionRule
Number of unitsMore than one on a non-detached house or block of flats. More than two on a detached house
SizeThe outdoor unit is over 1.5 cubic metres on a house, or over 0.6 cubic metres on a block of flats
RoofIt is on a pitched roof, or within 1 metre of the edge of a flat roof
Protected sitesThe building is listed, or the site is a scheduled monument
Conservation areasIt is on a wall or roof that fronts a highway
ElsewhereIt is above the ground floor on a wall that fronts a highway
Wind turbinesThere is a wind turbine on the building or within its grounds
NoiseIt does not comply with MCS 020 a)

If any condition is not met, the heat pump needs full planning permission from your council.

Wales: new rules from 1 June 2026

The Welsh Government says permitted development rights for air source heat pumps "were updated on 1 June 2026". gov.wales now says "your installation must comply with MCS 020(a)". The main conditions:

  • Up to two heat pumps on a detached house, and one on other homes.
  • The outdoor unit must not exceed 1.5 cubic metres.
  • Not on a pitched roof, or within 1 metre of the edge of a flat roof.
  • Not on a listed building or within its grounds.
  • In a conservation area, not on a wall or roof that fronts a highway.

MCS's article on the Welsh changes says two units running together must stay within "the 40 dB limit". That differs from the 37 dB(A) in MCS's consultation response. We could not access the full standard to settle this. Ask your installer for the calculation on your home.

Scotland: Class 6H

Scotland has its own permitted development rules. The Scottish Government's Planning Circular 1/2024 covers air source heat pumps under Class 6H. The main conditions:

  • Only one air source heat pump on the building or within its grounds.
  • It must not protrude more than 1 metre from a wall, roof plane, roof ridge or chimney.
  • Not within the grounds of a listed building, or in a World Heritage Site.
  • In a conservation area, only at ground floor level on the rear of the home.
  • It must "comply with MCS (Microgeneration Certification Scheme) Planning Standards for air source heat pumps" or equivalent standards.

The circular does not set a dB figure itself. In May 2025, MCS said Scotland and Northern Ireland "must continue to comply with MCS 020 until further notice".

If your neighbour's heat pump seems too loud

There are two separate routes in England and Wales. You can use either or both.

RouteWhen it appliesWho to contact
PlanningThe heat pump does not meet the permitted development conditions, including MCS 020 a)Your council's planning team
Statutory nuisanceThe noise is "prejudicial to health or a nuisance"Your council's environmental health team

The statutory nuisance rules are in section 79 of the Environmental Protection Act 1990. They cover "noise emitted from premises so as to be prejudicial to health or a nuisance". When a resident complains, the council must take "such steps as are reasonably practicable to investigate the complaint". If it is satisfied a nuisance exists, section 80 says it "shall serve" an abatement notice. That applies even if the heat pump passed MCS 020 a) when it was installed.

This version of section 79 covers England and Wales only. Scotland has its own version. Talking to your neighbour first is often quickest. They may be able to change the unit's settings or position.

The Institute of Acoustics and the Chartered Institute of Environmental Health publish joint guidance for professionals. It uses a 37 dB(A) criterion for most installations, in line with MCS 020 a).

How far does a heat pump have to be from a neighbour's window?

In England there is no fixed distance in the law. Class G of the permitted development rules sets no boundary or window distance. MCS says the old 1 metre boundary rule was removed on 29 May 2025. What matters is whether the installation passes the MCS 020 a) noise calculation for your home.

Vaillant gives its own placement advice. It suggests the heat pump is placed "at least three metres away from your neighbours' property". It also says to "avoid positioning the heat pump near windows, especially bedroom windows". Vaillant warns that wall niches and corners "can amplify noise like an echo". This is a maker's recommendation, not a legal rule.

Quiet mode and night settings by brand

Most heat pumps have a quiet or night setting. It lowers the outdoor unit's noise by limiting its output. Each maker documents its own version:

BrandWhat the maker documents
Daikin AlthermaQuiet mode with levels "Quiet", "More quiet" and "Most quiet". It can run on a schedule
Octopus CosyA "Hush" setting in the app that limits the heat pump's top output
VaillantA night mode that lowers output at night. Vaillant says storage and underfloor heating help keep the home warm
Mitsubishi EcodanIts FTC6 controller lists "multiple quiet mode options". The product page gives no detail

Daikin

Daikin's user reference guide for the Altherma low temperature split says: "You can use quiet mode to decrease the sound of the outdoor unit." The menu path is User settings > Quiet > Activation. Choose a level, Off or Automatic. Automatic follows a schedule. You set it under User settings > Quiet > Schedule.

Daikin warns that quiet mode "also decreases the heating capacity of the system". It recommends not using the most quiet level when the outdoor temperature is below zero.

Octopus Cosy

Octopus says the Hush setting, in the Settings section of its app, "makes your Cosy even quieter". It limits the heat pump's "top end" output. Octopus describes that as output you would only need on the coldest days.

Vaillant

Vaillant says night mode lets you "lower the heat pump's output at night, reducing noise significantly". It suggests running hot water heating in the early morning. Vaillant does not give the menu steps on that page, so check your controller's manual or ask your installer.

Every maker that explains the trade-off says the same thing: a quieter setting means less heat. If your home struggles to stay warm on cold nights, ask your installer before you use the quietest level.

Quick answers

What is the heat pump noise limit in the UK?

  • In England and Wales, permitted development installations must pass MCS 020 a), which MCS says sets a 37 dB(A) limit. Scotland requires MCS Planning Standards under its own Class 6H rules.

Has the heat pump noise limit changed from 42 to 37 dB?

  • The number changed because the calculation changed. MCS removed the background noise steps, so the two figures are not directly comparable.

Do I need planning permission for a heat pump?

  • Not in England if it meets the Class G conditions and MCS 020 a). Listed buildings and some conservation area positions need permission.

How close to the boundary can a heat pump be?

  • Since 29 May 2025, MCS says heat pumps in England can go within 1 metre of the boundary. The noise calculation still has to pass.

How many heat pumps can I have without planning permission?

  • Two on a detached house and one on other houses or blocks of flats, under Class G.

Can I complain about my neighbour's noisy heat pump?

  • Yes. In England and Wales, contact your council's environmental health team. The council must take reasonably practicable steps to investigate a statutory nuisance complaint.

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

  • Usually not. Since 1 June 2026, gov.wales says installations under permitted development must comply with MCS 020(a) and meet the size and position conditions.

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

  • Usually not for one air source heat pump that meets Class 6H. Listed buildings, World Heritage Sites and some conservation area positions are excluded.

How far from a neighbour's window does a heat pump need to be?

  • In England there is no fixed distance in the law. The heat pump must pass the MCS 020 a) noise calculation. Vaillant suggests at least three metres from a neighbour's property.

Is there a way to make a heat pump quieter at night?

  • Yes. Most makers offer a quiet or night mode. Daikin, Octopus and Vaillant all document one. It reduces noise by limiting output.

Does quiet mode reduce heating?

  • Yes. Daikin says quiet mode "also decreases the heating capacity of the system".

Are heat pumps noisy for neighbours?

  • The MCS 020 a) calculation exists to protect neighbours. Ask your installer to show you the calculation for your home before you agree to a position.

Sources, checked 6 November 2026:

  • Heat pumps
  • Planning
  • Permitted development
  • Home heating

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