Heat pump evidence for a planning energy statement
Most domestic heat pumps need no application. The condition that decides it is the MCS noise standard, calculated at 1 metre from a neighbouring habitable room window.
Most domestic air source heat pumps need no planning application and no energy statement. They are permitted development under Schedule 2 Part 14 Class G of the Town and Country Planning (General Permitted Development) (England) Order 2015, subject to conditions, and the condition that matters is the noise one: the installation has to comply with the MCS planning standard, which sets a calculated limit of 42 dB(A) at an assessment position 1 metre from a habitable room window or door of a neighbouring property.
Get the noise calculation right and the rest follows. Get it wrong, or skip it, and a council enforcement officer can take the view that the right never applied, which puts an installed unit outside permitted development with no fallback.
When a heat pump needs consent at all
Class G permits an air source heat pump on domestic premises, with limitations covering the size of the outdoor unit, its siting, its appearance and its removal when no longer needed. The limitations were relaxed by amendment in 2024, so read the current text of Part 14 rather than a guide written before then.
Consent is needed in these situations:
- The dwelling is a listed building, or the unit would go within its curtilage, where the right does not apply and listed building consent is likely to be needed as well
- The property is in a conservation area, a National Landscape, a National Park or a World Heritage Site and the unit would go on a wall or roof slope forming the principal or side elevation fronting a highway
- The unit exceeds the volume limit for the outdoor compressor, or the siting falls outside the distances the class allows
- The installation cannot meet the MCS noise standard at the neighbouring assessment position
- An Article 4 direction has removed the right locally, which is uncommon for Class G but not unknown in conservation areas
Flats are a separate question. Class G applies to domestic premises including blocks of flats in some circumstances, with different limits, and a unit serving one flat on a shared elevation often needs permission. Check the class text and the lease.
The noise assessment a council expects
The MCS planning standard works by calculation rather than measurement. You take the manufacturer's declared sound power level for the unit at its rated operating condition, apply a distance correction to the assessment position, and apply corrections for reflective surfaces and for any barrier between the unit and the window.
The three variables you control are distance, enclosure and the unit itself. Doubling the distance to the neighbouring window takes roughly 6 dB off the result in free field conditions. A unit sited in a corner between two walls gains several decibels from reflection, which is why the convenient spot beside the back door often fails. And manufacturers publish a sound power figure that varies substantially between models of similar output, so the specification is a design decision rather than an afterthought.
Submit the calculation sheet, the manufacturer's data sheet, and a plan showing the unit, the assessment position and any reflective surface or barrier. Where the result sits within a decibel or two of the limit, an acoustician's check is money well spent, because a marginal calculation is the thing an objecting neighbour will take apart.
Siting distances and boundary relationships
The class sets siting rules and the 2024 amendments changed them, so the current text governs. Beyond the rules, three practical judgements decide whether an installation causes trouble.
Keep the unit away from the neighbour's bedroom window rather than away from the boundary. A unit 3 metres from a boundary with a blank wall beyond is quieter at the receptor than one 5 metres away facing a window.
Point the fan discharge into open space, not at a wall that will reflect it back across the garden. And leave the clearances the manufacturer specifies for airflow, because an installation boxed in to hide it will run harder, ice up in cold weather and make more noise than the data sheet predicts.
Front gardens are the hardest case. A unit visible from the street in a conservation area will attract attention even where the right technically applies, and a side or rear position with a longer pipe run is usually the better outcome.
Flow temperatures and emitter sizing evidence
This is building regulations territory rather than planning, and it still belongs in the paperwork because it decides whether the installation works. Approved Document L expects new and replacement heating systems in existing dwellings to be designed to a maximum flow temperature of 55 degrees Celsius where that is practical, and heat pumps run most efficiently well below that.
A low flow temperature means larger emitters. A room heated by a single panel radiator at 70 degrees needs a substantially larger surface at 45 degrees, which in practice means a double panel, a wider unit or underfloor heating. The room-by-room heat loss calculation is the document that proves the sizing, and it is a requirement of the installation standards rather than of planning.
Where a local plan policy does require an energy statement, for example on a larger householder scheme in London or on a new dwelling, the heat pump sits in the carbon reduction section of an Energy Statement, supported by the heat loss calculation and the predicted performance. For a single retrofit on an existing house, no such document is needed.
Interaction with listed building and conservation area controls
For a listed building, the question is whether the installation affects the character of the building as one of special architectural or historic interest. A unit on the ground in a rear garden, with pipework entering through an existing opening, may well not. A unit fixed to a principal elevation, or pipework cut through a moulded cornice, certainly will.
The usual route is listed building consent with a short Heritage Statement covering the significance of the affected fabric, the alternatives considered, and the reversibility of the fitting. Reversibility carries real weight here: a bracket fixed into a mortar joint rather than into stone, a pipe route through an existing hole, and a unit that can be removed without trace.
In a conservation area without a listing, the test is the effect on the character and appearance of the area, which comes down to visibility from the street and other public viewpoints. Screening with timber louvres or planting helps, provided the airflow clearances are kept.
What to include in the submission
| Document | When it is needed |
|---|---|
| MCS noise calculation with the manufacturer's data sheet | Always, whether or not an application is made |
| Site plan showing the unit, assessment position and barriers | Always |
| Elevations showing the unit in position | Where permission or listed building consent is sought |
| Heritage statement | Listed building, or conservation area where visibility is an issue |
| Room-by-room heat loss calculation | For the installation standards, and useful evidence of competent design |
| Energy statement | Only where a local plan policy requires one |
| Acoustician's review | Where the calculated result is close to the 42 dB(A) limit |
Keep the noise calculation even where no application is made. It is the evidence that the permitted development condition was met, and the only answer to a complaint two years later.
Conditions typically attached
Where permission is granted, expect conditions on the finish and colour of the unit, screening to be installed and retained, a requirement that the unit be removed and the fabric made good when no longer needed, and a noise limit expressed either as the MCS standard or as a rating level at a stated position.
A condition requiring maintenance in accordance with the manufacturer's schedule is reasonable and worth offering. An installation that ices up because nobody cleared the leaves from the coil is both less efficient and louder.
Ground source systems raise entirely different questions around boreholes and abstraction, covered in ground source heat pumps and borehole permitting. Where the plant is larger and serves several dwellings, a full Noise Impact Assessment to BS 4142 replaces the MCS calculation.
PlanScope can draft the supporting statements for a heat pump application, including the heritage and noise material, from a postcode and a set of answers, flagging where measurements or manufacturer data are needed. Reports should be reviewed before submission and PlanScope does not guarantee planning approval. This is general guidance, not legal advice, and a lawful development certificate is the only formal way to confirm that an installation is lawful.
Frequently asked questions
Does an air source heat pump need planning permission?
Usually not. Class G of Part 14 of the General Permitted Development Order 2015 permits one on domestic premises subject to conditions, including compliance with the MCS planning standard for noise. Permission is needed for listed buildings, for certain positions in conservation areas and designated landscapes, and where the size or siting limits are exceeded.
What noise limit applies to a domestic heat pump?
The MCS planning standard sets a calculated limit of 42 dB(A) at an assessment position 1 metre from a habitable room window or door of a neighbouring property. It is a calculation using the manufacturer's declared sound power level with corrections for distance, reflective surfaces and barriers, rather than a measurement after installation.
Does a heat pump need an energy statement?
Only where a local plan policy requires one, which generally means larger schemes or new dwellings rather than a single retrofit. Where an energy statement is required, the heat pump belongs in the carbon reduction section, supported by the room-by-room heat loss calculation and the predicted performance figures.
Can I put a heat pump on a listed building?
Permitted development does not apply, so listed building consent is likely to be needed along with planning permission. The case turns on the effect on the building's special interest, so a ground-mounted unit in a rear garden with pipework through an existing opening is far easier to justify than a unit fixed to a principal elevation.
Why does siting a heat pump in a corner cause problems?
Reflective surfaces add to the calculated sound level. A unit in the angle between two walls can gain several decibels from reflection, which is why the convenient position beside the back door often fails the assessment while a more open position at a similar distance passes.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.