The Department for Energy Security and Net Zero published an independent review in November 2023 proposing amendments to the domestic air source heat pump (ASHP) permitted development right, according to an explanatory memorandum to the Town and Country Planning (General Permitted Development) (England) (Amendment) Order 20251. The review was published alongside changes to the Microgeneration Certification Scheme (MCS), which provides the noise assessment that all permitted development right ASHPs must meet1.
The memorandum states that the review proposed amendments "with the aim of supporting the government's heating decarbonisation ambitions"1. The previous Microgeneration Installation Standards: MCS 020, covering permitted development installations of wind turbines and air source heat pumps on domestic premises, was updated on 20 March 2025, separating the ASHP and wind turbine standards into two documents: MCS 020 a) for air source heat pump sound calculation and MCS 020 b) for wind turbine sound calculation1.
Following the review, the department then known as the Department for Levelling Up, Housing and Communities consulted on amendments to permitted development rights for off-street parking electric vehicle charging point infrastructure and ASHPs in February 20241. The consultation ran from 13 February to 9 April 2024 and received 1,409 responses in total, from organisations and individuals across the public, private and charitable sectors1.
The 2025 Order makes several changes to Class G of Part 14 of Schedule 2 of the General Permitted Development Order, which covers ASHPs on domestic premises1. The main changes are set out below.
| Change | Before | After |
|---|---|---|
| Distance from curtilage boundary | No part of the ASHP within 1 metre of the boundary | Limit removed1 |
| Permitted use | Heating only | Cooling and heating, but not solely for cooling1 |
| Outdoor compressor unit size threshold | 0.6 cubic metres per ASHP | 1.5 cubic metres per ASHP, for dwellinghouses only1 |
| Number of ASHPs | One per building or curtilage | Up to two, for detached dwellinghouses only1 |
| Noise standard | MCS 020 "or equivalent standards" | "or equivalent standards" removed; MCS 020 a) is the applicable standard1 |
The memorandum says the size threshold increase reflects the review's finding that a larger evaporator, a larger fan and a lower fan speed allow an ASHP to run more slowly to minimise noise further without compromising capacity1. The order also amends paragraph P of Part 14 to reference the updated MCS Planning Standards, and Article 7 provides transitional arrangements for the removal of "or equivalent standards"1.
The instrument extends to England and Wales, but its territorial application, meaning where it produces a practical effect, is England1. The memorandum states there are no plans to issue specific guidance for the instrument1.
Why it matters for households
Permitted development rights are a national grant of planning permission for specified development, which means householders can install certain equipment without submitting a planning application1. The changes to the ASHP right widen what can be installed under that route: an outdoor unit can now sit closer to a property boundary, a larger compressor unit is allowed, and a detached house can have two units rather than one1. The right now also covers cooling as well as heating, though not cooling alone, which the memorandum says will allow air-to-air heat pumps to benefit from the right and provide additional consumer choice1.
The removal of "or equivalent standards" is intended to give installers clarity that MCS 020 a) is the relevant standard for heat pump installations1. The memorandum notes that ASHPs are described as three times more efficient than traditional boilers, reducing household carbon emissions by around 70%, a figure that will increase further as the electricity grid decarbonises1. Noise remains the subject of the standard that permitted development installations must meet.
What happens next
The memorandum records that the MCS 020 standard was updated on 20 March 2025, separating the ASHP and wind turbine standards1. It states that the Department for Transport will consider the issue of cross pavement solutions in due course, in the context of concerns raised in consultation about electrical outlets nearer to the highway and trailing cables1. No further steps specific to the ASHP permitted development right are set out in the memorandum1.