Planning permission
Do you need planning permission for a heat pump?
- Covers
- air source heat pump, ASHP, air-to-water heat pump, air-to-air heat pump, ground source heat pump, water source heat pump, heat pump outdoor unit
- The law
- GPDO 2015, Schedule 2, Part 14, Class G (air source, as amended by SI 2025/560 from 29 May 2025), Class C (ground source) and Class D (water source)
- Applies to
- England
Short answer
Usually not, for a house in England. Part 14, Class G of the General Permitted Development Order grants permission for an air source heat pump on a house or in its garden, if it passes the MCS 020 a) noise calculation and stays within the size and siting limits. Since 29 May 2025 the outdoor unit of a house's heat pump can be up to 1.5 cubic metres, a detached house can have two, and the old rule keeping units 1 metre from the boundary has gone.
Ground source and water source heat pumps within the curtilage of a house or block of flats are permitted by Classes C and D, which set no size or siting limits of their own.
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The Class G limits for a house
| Test | Limit | Paragraph |
|---|---|---|
| Noise | Must comply with MCS 020 a) | G.1 |
| Number | One on a semi-detached or terraced house; two on a detached house | G.2(a) |
| Outdoor unit size | 1.5 cubic metres including housing (0.6 cubic metres on a block of flats) | G.2(d) |
| Wind turbine | None on the same building or in the curtilage | G.2(b), (c) |
| Roof | Not on a pitched roof; on a flat roof, at least 1 metre from the edge | G.2(f), (g) |
| Listed building | Not on it or in its curtilage | G.2(i) |
| Conservation area or World Heritage Site | Not on a wall or roof fronting a highway, and not nearer a bounding highway than the house | G.2(j) |
| Anywhere else | Not above ground floor level on a wall fronting a highway | G.2(k) |
| Use | Not used solely for cooling | G.3(aa) |
A "detached dwellinghouse" is one that does not share a party wall with a neighbouring building (paragraph P). A link-detached house joined by a garage wall may only get one.
G.1 Development is not permitted by Class G unless the air source heat pump complies with the MCS Planning Standards.
The noise test replaced the boundary rule
Before 29 May 2025 no part of the heat pump could be within 1 metre of the boundary, the outdoor unit was capped at 0.6 cubic metres, and only one was allowed. Guidance written before that date gives those limits. The government's explanatory memorandum explains that the independent review of heat pump noise found the boundary distance unnecessary, given a noise limit at neighbouring homes.
MCS 020 a) (issue 1.1, 14 April 2025) sets a permitted development noise limit of 37 dB LAeq,5mins at each assessment position: 1 metre outside the centre of any door or window to a habitable room of a neighbouring home. With two units, the calculation covers both together (Table 2 of the standard). The installer completes the calculation table and must give you a copy; keep it with the house papers, because it is your evidence that the installation is permitted development.
Conditions that last
The unit must be sited, so far as practicable, to minimise its effect on the building's appearance and the amenity of the area, and removed when no longer needed (paragraph G.3). The old condition that it be used solely for heating was replaced by one that it is not used solely for cooling: see air conditioning.
Ground source and water source
Classes C and D grant permission for a microgeneration ground source or water source heat pump within the curtilage of a house or block of flats, with no "development not permitted" paragraph at all. For heat, microgeneration is capped at 45 kilowatts thermal (Energy Act 2004, section 82(6) and (8)). Listed building consent can still be needed for works to a listed building, and an article 4 direction can still remove the right.
Flats and listed homes
On a block of flats the limits are one heat pump for the whole block and 0.6 cubic metres: see flats and maisonettes. For listed houses and conservation areas, see solar panels and heat pumps on heritage homes. The permitted development checker runs through the Class G tests.
Getting certainty
A lawful development certificate under section 192 of the Town and Country Planning Act 1990 confirms that a proposed heat pump would be lawful; the council has 8 weeks to decide. Include the MCS 020 a) calculation with the application. See lawful development certificates.
Sources
- GPDO 2015, Schedule 2, Part 14 (Classes C, D and G, paragraph P) legislation.gov.uk
- The Town and Country Planning (General Permitted Development) (England) (Amendment) Order 2025, SI 2025/560 legislation.gov.uk
- Explanatory memorandum to SI 2025/560 legislation.gov.uk
- MCS 020 a) Air Source Heat Pump Sound Calculation, issue 1.1 mcscertified.com
- Energy Act 2004, section 82 legislation.gov.uk
- Town and Country Planning Act 1990, section 192 legislation.gov.uk