Heat pump planning permission: when you need it, when you don’t

Class G: the limits for air source heat pumps in England

Permitted development rights let you do certain work without a planning application. For air source heat pumps in England, the right is Class G of Part 14 of Schedule 2 to the Town and Country Planning (General Permitted Development) (England) Order 2015. It grants permission for the installation, alteration or replacement of a microgeneration air source heat pump on a dwellinghouse or block of flats, or within the curtilage of one, including on a building within the curtilage. The legislation.gov.uk text, checked on 8 October 2026, states it is up to date with all changes known to be in force on or before 8 October 2026, and none of the outstanding changes it lists touches Class G.

The right is then limited. Development is not permitted if any of these apply (paragraph G.2):

The Order also attaches three further conditions: the unit must, so far as practicable, be sited to minimise its effect on the external appearance of the building and on the amenity of the area, and it must be removed as soon as reasonably practicable when no longer needed. Outside the limits you apply for planning permission. The council may still grant it; the limits only set out what is automatically allowed. Note the last row of the table, which many summaries leave out: even away from a conservation area, a unit cannot go on a wall facing the road above ground-floor level.

What changed on 29 May 2025

The Town and Country Planning (General Permitted Development) (England) (Amendment) Order 2025 (S.I. 2025/560) came into force on 29 May 2025. A lot of older advice, including some still on installer sites, predates it. Its changes to Class G were:

• The boundary rule was omitted. Paragraph G.2(e), the condition that tied the unit’s position to the property boundary, no longer exists.
• Detached houses can have two units, where the previous limit was one air source heat pump.
• The size limit rose to 1.5 cubic metres for a house, with 0.6 cubic metres kept for a block of flats.
• The definition of the MCS Planning Standards was updated to refer to MCS 020 a), the air source heat pump sound standard.
• A cooling-only condition was added: a unit used solely for cooling is not permitted development.

If you see “42 dB” or “one metre from the boundary” on a page about heat pump planning, it is out of date: the permitted development limit in MCS 020 a) is 37.0 dB(A).

If you live in a flat, the smaller volume limit and the freeholder’s consent usually decide the matter before planning does; the guide to heat pumps for flats and terraces works through the positions.

Listed buildings, conservation areas and Article 4 directions

If the house or block of flats is listed, Class G does not apply to a unit on the building or on land in its curtilage. You need planning permission, and listed building consent may also be needed for work that affects the character of the building; both are separate regimes run by the council. The same applies to a scheduled monument site. In a conservation area or World Heritage Site the right still exists, but with the stricter position test above. That test is about where the unit goes relative to the highway, not whether it can be seen: a unit round the side of the house that is nearer to the road than the front wall is still excluded.

Councils can also take permitted development rights away. Under article 4 of the Order, the Secretary of State or a local planning authority can make a direction that development of a specified class, or particular development, no longer enjoys the permission the Order grants. If you live in a conservation area or an area with a history of local restrictions, ask the council whether a direction covers your street. Old and protected houses raise wider questions than planning; for those see heat pumps in old houses.

In the capital, conservation areas and highway-facing walls often decide where a unit can go; the London guide covers the borough data alongside those siting questions.

The noise condition

This is the condition that most often makes the difference in practice, and it is the installer’s calculation to carry out. MCS 020 a) sets a permitted development noise limit of 37.0 dB(A), measured as LAeq,5mins, at an assessment position: a point 1 metre outside the centre of any door or window of a habitable room of a neighbouring property, with the effect of the facade ignored. The standard is explicit that compliance with it does not on its own bestow permitted development rights, and that the other conditions of the Order must also be met. The details, including how distance, reflecting surfaces and barriers affect the result and a calculator you can try, are in heat pump noise and the 37 dB(A) rule.

Ground and water source heat pumps

Class C of the same Part grants permission for the installation, alteration or replacement of a microgeneration ground source heat pump within the curtilage of a dwellinghouse or block of flats. Class D does the same for a water source heat pump. Neither contains the number, volume, roof or noise limits that Class G places on air source units. That does not make a ground source project consent-free in every case: listed building consent and article 4 directions sit outside Part 14, so check with the council if either might apply. The grant side of ground source is on the ground source heat pump grant page.

Worked scenarios

Wales, Scotland and Northern Ireland

Planning is devolved, so the Class G limits above are England’s. The Boiler Upgrade Scheme is covered separately on grants by country.

Wales

The Welsh Government says domestic heat pumps benefit from permitted development rights, and its page records that the air source rules were updated on 1 June 2026 by the Town and Country Planning (General Permitted Development) (Amendment) (Wales) Order 2026. On 8 October 2026 the page listed conditions broadly like England’s: compliance with MCS 020 a), up to two units on a detached house and one otherwise, an outdoor unit of no more than 1.5 cubic metres, no pitched roofs, no listed buildings, restrictions on highway-facing walls and roofs, and no cooling-only units. Read the Welsh page itself for the current wording before you rely on any of this; the table in this guide is England only.

Scotland

Scotland has its own order and its own classes. The Scottish Government’s Planning Circular 1/2024, published 28 May 2024, describes Class 6H for air source heat pumps on a dwelling or in its curtilage, with limits that include no more than one air source heat pump on the same building or curtilage, no protrusion of more than 1 metre from a wall, roof plane, ridge or chimney, a conservation-area limit to ground-floor rear elevations, no installation in a World Heritage Site or the curtilage of a listed building, and a requirement to comply with the MCS planning standards for air source heat pumps or equivalent. Scottish rules have been under review, so confirm the current position with your council. Scottish grants (Home Energy Scotland, not the Boiler Upgrade Scheme) are on the Scotland section.

Northern Ireland

Northern Ireland has its own planning system, and this guide has not sourced its heat pump rules, so it does not state any. Ask your council. For funding in Northern Ireland, see what exists and what has closed.

If you want certainty, and how this fits the grant

You can apply to the local authority for a lawful development certificate for proposed development. GOV.UK guidance says that, once granted, any proposed use or development in accordance with it must be presumed lawful unless there is a material change before it begins, and a fee applies. It is worth considering when the position is borderline, for example on a corner plot or in a conservation area.

Ofgem’s property owner guidance (v5.1) does not list planning permission among the grant’s conditions; it mentions planning evidence only for self-build properties. The scheme pays £7,500 towards air source and ground source installations (£9,000 for eligible off-gas oil and LPG homes for applications up to 31 March 2027), through an MCS-certified installer who applies on your behalf. If you do need permission, build the time into the plan: vouchers last 3 months for air source and 6 for ground source. How applications work is in how to apply; you can check your grant position below.