MCS 020 noise calculator

Will the heat pump pass the permitted-development noise limit?

Check the sound pressure at a neighbour’s window against the MCS 020 (a) permitted-development limit before you quote the job. Enter the sound power figure, the surroundings and the distance, and the working is shown line by line.

A pre-check to size up a survey, not the MCS 020 compliance submission. England uses MCS 020 (a). Nothing is sent anywhere.

1. Where is the property?

England uses MCS 020 (a), a 37.0 dB(A) limit. Scotland, Wales and Northern Ireland still use the earlier MCS 020 (42 dB(A) including a 40 dB(A) background), which this tool does not compute.

2. The heat pump and the window

The assessment position is 1 m outside the centre of a neighbour’s nearest habitable-room window or door. Run the check for each one; the worst case governs.

A-weighted sound power level from the datasheet. Use the highest specified figure, not the low-noise mode.dB(A)
Any hard surface within 1 m, including the ground, but not vegetation. More surfaces make it louder.
Straight line from the centre of the unit to the window, to the nearest 0.1 m.m

3. Any barrier in between

A solid wall or fence that blocks the line of sight from the top of the unit to the window reduces the noise. Open or gappy fences and vegetation do not count.

dB(A)
m

Sound pressure at the window

Permitted-development limit37.0 dB(A)

Working

Sound power level
Directivity
Distance and directivity
Barrier correction
Heat pumps

Computed with the MCS 020 (a) method: LP = LW + 10·log(Q / 4πr²) minus the barrier correction, compared against 37.0 dB(A). It is a pre-check, not the MCS 020 (a) submission, and your local planning authority has the final say.

Scotland, Wales or NI

Different standard appliesScotland, Wales and Northern Ireland still use the earlier MCS 020, which allows up to 42 dB(A) and includes a 40 dB(A) background in the assessment. This tool computes the England MCS 020 (a) method (37.0 dB(A), no background), so it will not give you the right figure here. Use the MCS 020 paper form or Excel tool for your nation. Capture it on the survey instead →
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Heat pump noise pre-check

MCS 020 (a) permitted-development method (England). Not the compliance submission.

Reference: Date:
InputValue
Sound power level (highest datasheet figure)
Directivity (reflecting surfaces)
Distance to assessment position
Barrier
Sound pressure at the assessment position
Against the 37.0 dB(A) limit
MCS 020 (a) permitted-development noise pre-checkPermitted-development limit 37.0 dB(A) at the assessment position (1 m external to the centre of a neighbour’s habitable-room window or door). England, MCS 020 (a) Issue 1.1.

A pre-check to size up a survey, not the MCS 020 (a) compliance submission. Results depend on the manufacturer sound power figure and the inputs chosen. Complete the official MCS 020 (a) paper form or Excel tool for the planning record; the local planning authority has the final say. Scotland, Wales and NI use the earlier MCS 020. installHUB does not issue MCS certificates.

Produced with the free tools at installhub.com/tools
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The method

How the MCS 020 (a) noise check works

Six lines. The arithmetic is standard point-source acoustics, so no copyright tables are reproduced.
Sound power levelThe A-weighted sound power level LW from the datasheet, in dB(A). Use the highest specified figure, never the low-noise mode, because the unit will not always run quietly.
Directivity QMore hard surfaces within 1 m reflect more sound back: Q2 for one surface, Q4 for two, Q8 for three. The ground counts, vegetation does not. More than three surfaces (a lightwell) cannot meet the standard.
Distance and directivityThe sound spreads out with distance: 10·log(Q / 4πr²), where r is the straight-line distance in metres to the assessment position.
Barrier correctionA solid barrier (Type 1 ≥18 mm, Type 2 <18 mm) that blocks the line of sight takes off up to 10 dB. Open or gappy fences and vegetation take off nothing.
The limitLP = LW + 10·log(Q / 4πr²) minus the barrier correction, rounded to 0.1 dB. 37.0 dB(A) or lower at every assessment position may be permitted development under MCS 020 (a).
Two heat pumpsEach unit’s sound pressure is worked out, then combined with a logarithmic sum. Three or more units are a full planning matter.

Which standard applies. In England the governing document is MCS 020 (a) Issue 1.1, mandatory for permitted-development heat-pump installs from 20 September 2025, with a 37.0 dB(A) limit applied to the heat pump alone. Scotland, Wales and Northern Ireland still use the earlier MCS 020, which allows up to 42 dB(A) and includes a 40 dB(A) background. This calculator does the England method and is a pre-check, not the official submission: complete the MCS 020 (a) form or Excel tool from mcscertified.com for the planning record.

Passing the noise check is step one

The job still needs surveying, documenting and, more often than not, a DNO notification, because a heat pump adds a continuous electrical load. installHUB captures the unit location, the photos and the noise working on the survey, then carries it through to the quote, the job sheet and the DNO notification without re-keying.

Capture it on the survey →Will it need a DNO notification? →Check the supply →
Questions

Heat-pump noise and MCS 020, answered

What is the MCS 020 noise limit for a heat pump?+

In England, under MCS 020 (a), the sound pressure from the heat pump must be 37.0 dB(A) or lower at the neighbour’s assessment position for the install to count as permitted development on noise. The earlier MCS 020, still used in Scotland, Wales and Northern Ireland, allowed up to 42 dB(A) and included a 40 dB(A) background in the assessment.

What is the "assessment position"?+

A point 1 m outside, and perpendicular to, the centre of the nearest window or door to a habitable room of a neighbouring property. A habitable room is one used for sleeping or living, not a bathroom, hallway, utility or similar. Run the check for each neighbouring window and door, because the worst case governs.

Which heat-pump sound power figure do I use?+

The highest A-weighted sound power level on the datasheet, not the low-noise or night-mode figure. The unit will not always run in its quiet mode, so the assessment has to use the worst case. For MCS-certified products the figure is published on the MCS Product Directory.

Do reflecting surfaces make it louder?+

Yes. A hard surface within 1 m of the unit reflects sound back and raises the level at the window: Q2 for one surface, Q4 for two, Q8 for three. The ground counts, vegetation does not. More than three surfaces, such as a unit in a small lightwell, cannot meet the standard.

Does a fence or wall help?+

A solid barrier that blocks the line of sight from the top of the unit to the window reduces the noise. A solid masonry wall or fence at least 18 mm thick (Type 1) that fully obscures the window takes off up to 10 dB. Open, gappy or poorly maintained fences and vegetation take off nothing.

My result is over the limit. What now?+

Move or raise the unit, add distance to the neighbour’s window, add a solid barrier, choose a quieter unit, or apply for full planning permission. Re-run the check after each change, and for every neighbouring window and door.

Is this the official MCS 020 submission?+

No. This is a pre-check to help you size up a survey and spot a problem early. The planning record needs the official MCS 020 (a) paper form or Excel tool from mcscertified.com, and your local planning authority has the final say. installHUB does not issue MCS certificates.

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