Heat Pump Planning Rules: The 1-Metre Boundary Rule Is Gone
The 1-metre boundary rule for heat pumps was scrapped in 2025. New limits cover unit size, the number of units, and a 37 dB(A) noise test. Here is what you can fit without permission.
If you looked into a heat pump a couple of years ago and gave up because the unit had to sit a metre from the boundary, it is worth looking again. The permitted development rules in England were significantly relaxed in 2025, removing the single biggest obstacle for terraces and smaller homes. Here is what changed and what it means for your quote.
What changed in 2025
The permitted development rules for air source heat pumps were widened in England on 29 May 2025, by the Town and Country Planning (General Permitted Development) (England) (Amendment) Order 2025 (SI 2025/560). It amended Class G of Part 14, Schedule 2 of the 2015 Order. The requirement to site the unit at least 1 metre from the property boundary was deleted outright. The maximum size of the outdoor compressor unit on a house rose from 0.6 cubic metres to 1.5 cubic metres, though a block of flats stays at 0.6 cubic metres. Up to two units are now allowed on a detached house, and one on any other house or a block of flats. The old condition that the pump be used solely for heating was replaced by a condition that it must not be used solely for cooling, which is what lets a unit that also cools qualify. The installation must still comply with the MCS Planning Standards, now MCS 020 (a) for air source heat pumps, which sets a sound limit of 37 dB(A) at the assessment position. Scotland, Wales and Northern Ireland set their own permitted development rules and are not covered here.
The headline for most people: the 1-metre boundary rule that ruled out so many smaller homes is gone.
Why this matters
The old 1-metre rule meant a typical terraced or semi-detached home often had nowhere compliant to put the unit without applying for planning permission, which added cost, delay, and uncertainty. Removing it, and increasing the size allowance, makes a heat pump permitted development for far more homes. Combined with the Boiler Upgrade Scheme grant, the practical barriers have come down on both planning and cost.
The noise test is the new gatekeeper
With the boundary rule gone, the condition that does the most work is noise.
Permitted development still requires the installation to comply with the MCS Planning Standards. For air source heat pumps that is MCS 020 (a), which sets a sound limit of 37 dB(A) at the assessment position, taken at a neighbouring property's habitable room opening. Where the unit sits close to a neighbour, this calculation is the step that decides whether it qualifies as permitted development. A good installer does the MCS 020 calculation as part of the design and includes it. A quote that places a unit tight against a party boundary with no mention of the noise assessment has skipped a compliance step that could later cause a dispute.
What still needs permission
Permitted development is not universal. Class G still excludes a long list of situations, and these survived the 2025 relaxation untouched. You need planning permission if:
- The unit would go on a pitched roof. That is barred outright
- The unit would go on a flat roof within 1 metre of the external edge of that roof. One 1-metre rule went, this one did not, so do not read the headline as meaning no distance limits remain
- Your home is a block of flats, where the size limit is still 0.6 cubic metres and only one unit is allowed
- Your home is listed, or the site is a scheduled monument
- You are in a conservation area or a World Heritage Site and the unit would sit on a wall or roof fronting a highway, or nearer a highway than the house itself
- Anywhere else, the unit would go on a wall fronting a highway above ground floor level
- A wind turbine is already installed on the building or in the curtilage
- The installation exceeds the size or number limits
When in doubt, your council or installer can confirm. Our planning permission guide covers the wider picture.
What this means for your heat pump quote
A heat pump quote should now reflect the current rules, not the old ones.
Two things to check. First, that the quote is not still padding in a planning application you may no longer need (or, worse, assuming the old 1-metre rule and concluding you cannot have one). Second, that it includes the MCS 020 noise assessment where the unit is near a boundary. Our heat pump quote guide covers the full spec.
Check your quote
The rules changed recently enough that plenty of quotes and online advice are still out of date. Upload your heat pump quote and we check the spec, the grant, and the planning and noise position against the current rules, so you are not paying for an application you do not need or missing one you do. It takes under a minute.
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