Heat Pump Noise and Planning Rules for Landlords

The short answer

Check four things before you order: the property type, the position of the outdoor unit, the calculated noise at the nearest neighbour’s window and any listed building, conservation area or Article 4 restriction. Most ordinary houses can pass these checks. Flats, terraces and conservation areas need more care. This page covers England only and is not planning advice.

What Class G allows in England

Class G of the General Permitted Development Order covers installing an air source heat pump on a dwellinghouse or block of flats, or within its curtilage. As the text stands on legislation.gov.uk, development is not permitted if:

Rule	Limit
Number of units	One on a house that is not detached or on a block of flats; two on a detached house
Size of outdoor compressor unit, including housing	1.5 cubic metres on a house; 0.6 cubic metres on a block of flats
Pitched roof	Not permitted
Flat roof	Not within 1 metre of the roof edge
Listed building	Not permitted on the building or in its curtilage
Scheduled monument	Not permitted

Conditions also require the unit to be sited, so far as practicable, to limit its effect on the building’s appearance and the area’s amenity, and to be removed when no longer needed. A unit used solely for cooling is not covered.

Class G also says development is not permitted unless the heat pump complies with the MCS Planning Standards. From 29 May 2025 (SI 2025/560) those standards mean MCS 020 a) for air source heat pumps, the words “or equivalent standards” were removed, and an older rule about distance from the boundary was dropped. Do not rely on older guides that still quote the boundary rule.

The 37.0 dB(A) noise limit and MCS 020 a

MCS 020 a) is the MCS standard that sets out the sound calculation for a domestic heat pump to be permitted development. It uses a noise limit of 37.0 dB(A), measured as LAeq,5mins at an assessment position. That position is 1 metre outside the centre of a door or window to a habitable room of a neighbouring property.

For a landlord the key points are:

• Neighbouring property includes houses in multiple occupation, and on a block of flats it includes other flats in the block, apart from the owner’s own flat.
• The installer works from the manufacturer’s sound power data, the distance, the unit’s directivity and any barrier, and completes one table for each assessment position.
• The installer must keep one copy and give the customer another.
• MCS says compliance alone does not give permitted development rights, because other Class G limits still apply.

A tenant at the property is not the test. The calculation protects neighbours, which includes the tenants next door.

Flats and leasehold

A block of flats is limited to one unit and 0.6 cubic metres, so a second flat in the same block may find the single permitted unit already taken. Planning rules do not decide who may use an external wall or shared area. That depends on the lease and the freeholder, so read the lease and ask in writing. The flat air to air example shows why this matters for small flats.

Listed buildings, conservation areas and Article 4

• Listed building: Class G does not apply, so ask the local planning authority what consent is needed.
• Conservation area: the unit cannot go on a wall or roof that fronts a highway, or closer to the highway than the nearest part of the building.
• Elsewhere: a wall-mounted unit cannot sit above ground floor level on a wall that fronts a highway.
• Article 4 direction: a local authority can remove permitted development rights in an area. Ask the council whether one applies to the address.

If a neighbour complains

MCS 020 a) says an installation that does not meet the standard may be subject to enforcement action by the local planning authority, and that MCS may sanction a contractor who fails to ensure compliance. That is why the paperwork matters to you as the owner. If a neighbour or a tenant raises noise later, the completed calculation shows what was assessed and where.

Keep the sound table with the tenancy file and note the unit’s make and model. Siting also matters in practice: a unit facing a neighbour’s bedroom window across a narrow gap is a worse choice than one on a side wall with more distance, even if both calculate under the limit. Ask the firm to explain why it chose the position.

The 37.0 dB(A) figure comes from MCS 020 a), and Class G makes compliance with that standard a condition of permitted development. If the margin is tight, ask the local planning authority before the unit goes up.

What to ask the installer to provide

• The completed MCS 020 a) table for every assessment position, with the sound power figure used.
• The unit’s size including housing, and how many units are proposed.
• A plan or photo showing the position, and confirmation it is not on a pitched roof.
• Written confirmation that the listed building, conservation area and Article 4 checks were made.
• Their MCS details, which you verify on the register, as explained on the installer checking page.

More prompts are in questions to ask a heat pump installer as a landlord.

Next step

If the site passes these checks, test the economics in the heat pump landlord calculator or send an enquiry on the quote page. Relevant independent firms contact you; no charge to you, no obligation.