Solar Panels and Heat Pumps: Do You Need Planning Permission?

The short answer

For most houses, both solar panels and an air source heat pump can be installed under permitted development, with no planning application — and the heat pump rules were made more generous in 2025. The main exceptions are listed buildings, where consent is needed, and conservation areas, where some positions are restricted. As with all permitted development, the limits have to be met, and they do not apply to flats in the same way as to houses.

Solar panels

Panels on the roof of a house are permitted development provided they do not project more than 200mm from the roof slope, and are not fitted above the highest part of the roof (excluding the chimney). On a flat roof, the equipment must not stand more than 600mm above the highest part of the roof (excluding any chimney). From 27 August 2026, panels on a wall — and on a balcony or roof enclosure such as a balustrade, railing or parapet — may protrude up to 0.4 metres, or 0.2 metres where the wall or enclosure abuts a highway. In a conservation area or World Heritage Site, panels must not be fitted to a wall, balcony or roof enclosure that fronts a highway (a restriction widened from walls alone on 27 August 2026) — but roof-slope panels are usually still permitted development. Panels on a listed building need listed building consent, and the permitted development classes now expressly exclude a listed building and the buildings in its curtilage, so a planning application is needed as well.

Ground-mounted (stand-alone) arrays serving a house were substantially relaxed from 27 August 2026: more than one array is now allowed, and the old rule keeping every array at least 5 metres from the boundary has gone (it survives only in World Heritage Sites). The panels of each array are still capped at 9 square metres, the old 3-metre limit on any dimension is removed, and height is now tiered — broadly 4 metres, reducing to 2 metres within 5 metres of a boundary, 1 metre where that land is also forward of the principal elevation, and 2 metres in a conservation area where the array sits nearer the highway than the house. In that conservation-area position — and on other designated (article 2(3)) land within 5 metres of a boundary — a prior-approval application on the appearance of the array is needed before work starts. Flats keep the previous ground-mounted limits, and where the 2026 changes removed something that was permitted development before 27 August 2026, a transitional saving allows that work until the end of 26 August 2027.

Air source heat pumps — the 2025 changes

The permitted development rules for air source heat pumps were relaxed in England in 2025. The old requirement to site the unit at least one metre from the property boundary was removed; the size limit for the outdoor unit was increased to 1.5 cubic metres for a house (0.6 cubic metres for a flat); and detached houses may now have up to two heat pumps rather than one. The installation must still meet the MCS planning standard for noise (MCS 020), which controls the noise at neighbouring windows.

Conservation areas and listed buildings

The rights are narrower on protected buildings and land. Permitted development for a heat pump does not apply within the curtilage of a listed building, or on a scheduled monument, and in a conservation area the siting of a heat pump can be restricted — typically so that it is not on a wall or roof slope facing a highway. For solar, the conservation-area restriction falls on walls, balconies and roof enclosures fronting a highway rather than on roof slopes (widened from walls alone on 27 August 2026); a ground-mounted array in a conservation area sited nearer the highway than the house remains capped at 2 metres and still needs a prior-approval determination on its appearance, and from 27 August 2026 that prior-approval step also applies on other designated (article 2(3)) land within 5 metres of a boundary. Because so much of prime London is designated, it is worth confirming the position for your property before ordering equipment, and factoring any application into the programme.