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 in 2025. The requirement to site the unit at least 1 metre from the property boundary was removed. The maximum unit size was increased (from 0.6 cubic metres to 1.5 cubic metres). Up to two units are now allowed on a detached home. Air-to-air systems were brought in. The installation must still meet a noise condition assessed under MCS 020, in the order of 37 dB(A) at the nearest neighbour's habitable room window. Confirm the current conditions for your property type before relying on them.
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 meet a noise condition, assessed under MCS 020, roughly 37 dB(A) at the nearest neighbour's window. Where the unit sits close to a neighbour, this assessment 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. You are more likely to need planning permission if:
- Your home is a flat or maisonette (different, tighter rules)
- You live in a conservation area, and the unit would be on a wall or roof facing a road
- Your home is listed (listed building consent is a separate matter)
- 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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