Air source: Class G
Class G of Part 14 lets an air source heat pump be installed on a house or a block of flats, or in its grounds, without a planning application, if the conditions are met. As amended in 2025, they include:
- No more than one unit on a semi-detached or terraced house or block of flats, and no more than two on a detached house.
- The outdoor unit, with any housing, no larger than 1.5 cubic metres on a house or 0.6 on a block of flats.
- Not on a pitched roof, and not within 1 metre of the edge of a flat roof.
- The unit must comply with the MCS planning standard for sound, MCS 020 a).
- Not on a listed building or within its grounds, or on a scheduled monument.
- In a conservation area, not on a wall or roof fronting a road, or nearer the road than the house.
- Elsewhere, not on a road-facing wall above the ground floor.
The unit must also be sited, so far as practicable, to minimise its effect on the building's appearance and the area's amenity, and removed when no longer needed.
Ground and water source: Classes C and D
Class C covers the installation, alteration or replacement of a ground source heat pump within the grounds of a house or block of flats, and Class D does the same for a water source heat pump. The Part 14 text sets no further limits for these classes of the kind Class G sets. Digging trenches or boreholes may raise other questions, such as protected trees, drainage or archaeology, so check anything unusual about the site.
Listed buildings
The national planning dataset records 2,681 listed-building entries in Cheshire East, 2,542 in Cheshire West and Chester and 392 in Warrington. Class G does not apply to a listed building or land within its grounds, so an air source unit there needs planning permission, and listed building consent is likely where the work affects the building's character. See listed buildings.
Conservation areas
Each of the three councils has designated conservation areas. The national planning dataset does not yet hold a complete set for the three councils, so the councils' own maps are the reliable check. Inside a conservation area, Class G still applies but rules out road-facing positions; a unit at the back or side, no nearer the road than the house, usually works.
When to ask the council
- The building is listed, or you are not sure.
- The home is in a conservation area and the only workable position faces a road.
- The plan needs more units, a bigger unit or a pitched-roof position than Class G allows.
- You want certainty: a lawful development certificate confirms a plan is permitted development.
Lawful development certificates
A lawful development certificate is the council's formal confirmation that a proposal is lawful, for example because it meets Class G or Class C. It is optional. It is useful where a detail is uncertain, such as a corner plot, a flat roof or a home near a conservation area boundary, and it can help when selling. Apply to the council with a site plan, the unit's data sheet and, for an air source unit, the sound calculation.
The rules here are England's. Homes in this guide's three areas are all in England, so Class C, D and G apply as described.
The quickest check for a particular address is the council's own conservation area map and the list entry for any building nearby.