Low-carbon heating is now central to almost every planning energy statement, and the air source heat pump is the technology doing most of the work. England has recently made heat pumps easier to install under permitted development, which changes the calculus for both homeowners and larger schemes. This guide explains what the heat pump permitted development rules now allow, when you still need planning permission, and how a heat pump feeds into an energy statement.
What changed in the permitted development rules
Through 2025, England amended the General Permitted Development Order to make air source heat pumps far easier to install without a separate planning application. The key changes were:
- The old 1-metre boundary rule was removed, so a unit can now sit closer to a neighbour’s boundary provided the noise conditions are met.
- The maximum permitted unit size was raised from 0.6 m³ to 1.5 m³.
- Detached houses can install up to two air source heat pumps under permitted development.
- Combined heating-and-cooling units became eligible.
These changes remove a genuine barrier — the old boundary rule ruled out heat pumps for many terraced and small-garden properties.
The conditions still attached
Permitted development is not a free pass. The installation must still meet the MCS 020 planning standard for noise, demonstrating that sound at the nearest noise-sensitive neighbour does not exceed the permitted level (assessed at 37 dB(A)). The unit must be sited to minimise its effect on the amenity of the area and removed when no longer needed.
Crucially, permitted development rights are restricted or removed in some situations: on or near listed buildings, within the curtilage of a listed building, in conservation areas and other designated land the siting is tighter, and an Article 4 Direction can withdraw the rights entirely. Flats and maisonettes are also treated differently from houses. Always confirm the position with the local planning authority before installing.
Where the energy statement comes in
If your scheme needs planning permission — a new dwelling, a larger development, or a site where permitted development does not apply — the heat pump becomes part of your energy statement, not a standalone question. An energy statement works through the energy hierarchy: Be Lean, Be Clean, Be Green. It starts from the Part L 2021 baseline using the SAP 10.2 notional-building method, then demonstrates carbon savings at each stage. We explain the full sequence in what is an energy statement.
The heat pump sits at the Be Green stage as the low-carbon heat source, but it only performs if the Be Lean fabric measures come first. A well-insulated, airtight building lets a smaller heat pump run efficiently at low flow temperatures — the fabric-first logic set out in our fabric first guide. The carbon case against a gas boiler is now decisive on the SAP 10.2 emission factors, as we show in heat pumps vs gas boilers.
Looking ahead to the Future Homes Standard
The direction of travel is unmistakable. The Future Homes Standard, with its supporting guidance published in 2025, comes into force on 24 March 2027 and effectively ends new homes connecting to the gas grid, driving heat pumps and rooftop solar as standard, assessed through the successor calculation model SAP 10.3. Designing your heating strategy around a heat pump now future-proofs the scheme — see the Future Homes Standard and energy statements.
Air source or ground source?
Most planning energy statements assume an air source heat pump, because it is cheaper to install, needs no borehole or ground array, and now benefits from the relaxed permitted development rules described above. A ground source heat pump can deliver higher efficiency and is quieter externally, which occasionally matters on constrained or noise-sensitive sites, but the groundworks make it viable mainly on larger schemes or where a shared ground loop serves several dwellings.
For the energy statement, what counts is the resulting carbon saving under SAP, not the badge on the unit. Whichever type you choose, the modelling should show a system sized to a well-insulated fabric and running at a low flow temperature — an oversized heat pump on a leaky building is both expensive and poor value in carbon terms. Where a scheme genuinely cannot accommodate a heat pump, the statement must justify that and show how the carbon target is met by other means, such as increased solar or connection to a heat network at the Be Clean stage.
How Fortress Associates can help
Fortress Associates produces automated energy statements for UK planning applications. The report is free and ready in minutes, built on the Part L 2021 / SAP 10.2 baseline and working through the full Be Lean, Be Clean, Be Green hierarchy — including your heat pump and any rooftop solar — with CO₂ savings calculated at each stage. For London schemes it addresses the London Plan Policy SI2 35% target. Explore our services or contact us.
Sources & further reading
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