Heat pumps under Class G permitted development

Class G of Part 14 of Schedule 2 to the General Permitted Development Order 2015 allows an air source heat pump to be installed on domestic premises without planning permission, provided every condition attached to the class is met. Miss one condition and the whole class falls away, leaving you needing a householder application for a unit that is already bolted to the wall.

The conditions cover the equipment standard, where the unit sits, how big it is, what it is used for and what happens when it is no longer needed. Several of the numerical limits in England have been amended since the Order was made, so read the current consolidated text rather than a summary.

What Class G permits

The class covers installation, alteration or replacement of an air source heat pump on a dwellinghouse or a block of flats, or within the curtilage of a dwellinghouse or block of flats. It is permitted development, which means the right exists in the Order itself and there is nothing to apply for when the conditions are met.

Ground and water source systems sit in different classes in the same Part, with their own conditions, and they are generally less constrained because the plant is buried or submerged. If you have the land for a ground array, the planning position is usually simpler than for an external air source unit.

The class permits the heat pump. It does not permit everything that comes with it. New external pipework runs, a large buffer cylinder in an outbuilding, a raised plinth or an acoustic enclosure may each need looking at separately, and none of them is automatically covered.

The conditions, and which ones move

Group the conditions into the stable ones and the ones that have been amended, because that tells you where to check.

Stable in substance.

• The equipment must comply with the relevant microgeneration certification scheme planning standards, or equivalent standards.
• The heat pump must be used solely for heating purposes.
• It must be sited, so far as practicable, to minimise its effect on the external appearance of the building and on the amenity of the area.
• It must be removed as soon as reasonably practicable when no longer needed.
• It is not permitted within the curtilage of a listed building or a scheduled monument.
• Restrictions apply on article 1(5) land, which covers conservation areas, National Parks, National Landscapes, the Broads and World Heritage Sites.

Amended more than once in England, so check the current figures in the Order itself.

• The permitted volume of the outdoor compressor unit including its housing.
• Rules about proximity to the boundary of the curtilage.
• How many units may be installed under the class.
• The detail of roof installations, including the position on a flat roof.

The general prohibition on installing on a pitched roof has been a fixture of the class, and flat roof installations are subject to a setback from the external edge. Do not assume either point from memory when you are advising on a specific case.

Secondary legislation in this area is amended often. The same is true across the permitted development and use classes regimes, as our note on what the 2020 use classes reform replaced shows for a different part of the system.

The noise standard and how it is met

The reference to the certification scheme planning standards brings a noise test into the class, and that test is the condition most likely to be failed on a tight urban plot.

The assessment compares the sound level from the heat pump at an assessment position, taken at a habitable room window of the nearest neighbouring property, against a limit of 42 dB(A). The calculation accounts for the sound power of the unit, the distance, and the effect of nearby reflective surfaces such as walls and fences, which is why a unit in a narrow side passage between two houses performs much worse than the same unit in an open garden.

Practical consequences worth knowing before the installer arrives.

The calculation is done before installation, using manufacturer data, and your installer should hand you the completed sheet. Keep it. It is the evidence that the condition was met.

Position changes the answer more than the model does. Moving a unit two metres away from a boundary, or out of a reflective corner, will often bring a marginal case within the limit. Fences and walls close to the unit can make it worse rather than better.

Meeting the standard is not the end of the matter. A heat pump that complies can still, in principle, give rise to a statutory nuisance complaint if it is badly maintained or runs at antisocial hours, and that is dealt with by environmental health rather than through planning. Where a neighbour raises a serious objection at design stage, a short acoustic report from a competent consultant costs far less than a dispute, and on a complex site a full Noise Impact Assessment may be the proportionate answer.

Listed buildings, conservation areas and article 4

Three separate controls can each remove the right.

A listed building takes the installation outside the class entirely, and listed building consent is likely to be needed in any event for works affecting the special interest of the building or a structure within its curtilage. That includes internal works, so a new cylinder, pipe runs through historic fabric and radiator fixings can all be caught.

On article 1(5) land, the class continues to apply with extra restrictions focused on visibility from a highway. The general effect is that units on walls and roofs fronting a highway, or nearer to a bounding highway than the house itself, are excluded.

An article 4 direction removes permitted development rights in the area it covers. Directions over conservation areas are common and their scope varies, so check the authority's published list before assuming the class applies. Where a direction has removed the right, an application is needed, and the fee for development that would be permitted but for the direction is waived.

Flats, leases and shared roofs

The class extends to blocks of flats, with tighter conditions than for a house, and roof installations in particular are restricted.

Planning is only half the question. A leaseholder almost always needs the freeholder's consent under the lease for an alteration to the structure or the exterior, and for the use of a roof or a shared wall. That is a private law matter which planning permission does not resolve, and a permitted development right does not override a covenant.

Where several flats in a block want heat pumps, a coordinated scheme handled by the freeholder or management company works better than six separate installations. It also produces a sensible answer on noise, since cumulative sound from multiple units is assessed together rather than one at a time.

When a planning application is needed

Apply where any condition cannot be met, where the property is listed or an article 4 direction applies, where the unit needs to go on a highway-facing elevation in a conservation area, or where the noise calculation cannot be brought within the limit.

A householder application is the usual route. Submit a location plan, a block plan showing the unit position with distances to boundaries and neighbouring windows, elevations, the manufacturer's data sheet and the noise calculation. Add a photograph of the proposed position taken from the street. Refusals of well-sited rear garden units are not common, and the ones that do occur usually involve a very close neighbouring window or a prominent front elevation.

Where policy background is useful, the reform timeline on the planning law updates page is the place to follow changes to the Order.

Confirming the position before installation

If the installation relies on permitted development and anything about the case is marginal, get it confirmed rather than assumed.

A certificate of lawfulness for a proposed use or development under section 192 of the Town and Country Planning Act 1990 is the only formal way to confirm that works would be lawful. It carries a fee and a determination period, and it produces a decision notice you can show a buyer's solicitor. On a straightforward rear garden installation most people do not bother. On a corner plot where the side elevation arguably fronts a highway, it is money well spent.

Keep the paperwork either way: the data sheet, the noise calculation, the installer's certification, the commissioning record and photographs of the installed position with a tape measure in shot.

This is general guidance, not legal advice. Permitted development limits change, and a lawful development certificate is the only formal way to confirm that works are lawful, so check the current text of the Order and the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.

Browse all 66 PlanScope report types if an application turns out to be needed.