Do You Need Planning Permission for a Heat Pump in Truro?

The short answer

For most houses in Truro, no. Since 29 May 2025 an air source heat pump on a house in England is usually permitted development under Class G of Part 14 of the General Permitted Development Order, which means it does not need a planning application. Two situations change that in Truro more often than elsewhere in Cornwall: a house in the city conservation area where the unit would face the street, and a listed building, of which Truro has many.

What changed on 29 May 2025

The Town and Country Planning (General Permitted Development) (England) (Amendment) Order 2025 (S.I. 2025/560) relaxed the heat pump rules that had applied since 2011. Under the current Class G:

• Number of units: one air source heat pump on a terraced or semi-detached house, and up to two on a detached house.
• Size: the outdoor compressor unit can be up to 1.5 cubic metres on a house (0.6 cubic metres on a block of flats).
• Boundary: the old requirement to keep the unit at least a metre from the property boundary has been removed.
• Roofs: a unit still cannot go on a pitched roof, and on a flat roof it must be at least a metre from the edge.
• Cooling: the unit must not be used solely for cooling — a reverse-cycle unit that also heats is covered.

If you read older guidance mentioning a one-metre boundary rule or a 42 dB noise limit, it predates these changes.

The noise test: MCS 020 a)

Permitted development depends on the installation meeting the MCS planning standard for air source heat pumps, MCS 020 a). The calculation predicts the sound level at an assessment position one metre outside the nearest neighbouring habitable room window or door, and the permitted development limit is 37.0 dB(A). It takes account of the unit's sound power, the distance, any barrier between the unit and the window, and reflective surfaces near the unit. In a tightly packed Truro terrace the assessment usually decides which part of the yard or garden the unit can go in, so it is worth doing before you plan the pipe runs.

Truro's conservation area

Truro's conservation area covers the historic centre of the city, including Lemon Street. Inside a conservation area, Class G does not allow a heat pump:

• on a wall or roof that fronts a highway; or
• where it would be nearer to a highway that bounds the property than the part of the house nearest that highway.

This is a position test, not a visibility test. A unit in a rear yard that happens to be glimpsed from a side street is not caught simply because it can be seen; a unit on the front wall of a terrace is caught even if it is painted to match. For most conservation-area terraces in central Truro, the practical answer is a rear position that passes the noise assessment — which keeps the installation within permitted development.

A council can also remove permitted development rights on particular streets with an Article 4 direction, so we check the address with Cornwall Council's records before confirming that no application is needed.

Listed buildings on Lemon Street and Ferris Town

Class G does not apply to a listed building or to anything within its curtilage. Many houses on Lemon Street and in Ferris Town are listed, so a heat pump there needs planning permission, and listed building consent where the work would affect the building's character. For a heat pump the things that most often matter are the outdoor unit's position, where the refrigerant or water pipes pass through historic walls, and any change to internal features such as fireplaces or joinery when radiators are upsized.

Listed status does not mean a heat pump is off the table. It means the application has to show the siting and pipe routes clearly, so we design those at the survey rather than leaving them for installation day.

Ground source heat pumps

Ground source heat pumps are permitted development under a separate class (Class C) without the limits above. On larger plots around the edge of Truro that can make ground source the simpler planning route, although the ground works cost more and a listed building still needs consent for any works that affect its character.

Grants once planning is clear

Planning and funding are separate questions. The Boiler Upgrade Scheme pays £7,500 towards an air source or ground source heat pump, and until March 2027 an extra £1,500 — £9,000 in total — where the home is heated by oil or LPG and has no mains gas connection. An air-to-air heat pump in a home can get £2,500. Heat pumps installed in homes are zero-rated for VAT until 31 March 2027. The grant is claimed by your MCS-certified installer and taken off the invoice; our Boiler Upgrade Scheme guide for Cornwall covers eligibility in detail.

What to do next

Start with the address. If the house is listed, plan for an application; if it is in the conservation area, plan for a rear position; otherwise the noise assessment and the unit count are usually the only tests. Our surveys for heat pumps Truro homes cover all three — listed status, conservation area and the MCS 020 a) noise calculation — alongside the room-by-room heat loss that sizes the system. If you also want cooling, see air conditioning in Truro.