Air source heat pump planning permission: England’s 2026 rules

What to know first

This summary covers the main planning checks for an air source heat pump in England and the exceptions most likely to change the answer.

Most domestic installations in England do not need a planning application if they meet Class G. Permitted development is planning permission granted nationally for defined work; it does not mean planning controls disappear.

The present rules took effect on 29 May 2025.

When is an air source heat pump permitted development in England?

The installation, alteration or replacement of a microgeneration air source heat pump can qualify on a house or block of flats, or within its curtilage—the property’s garden or grounds. A block must consist wholly of flats, so a mixed residential and commercial building is outside this Class G description.

The table is a starting point. Local restrictions and the full statutory conditions still need checking.

These limits come from amended Class G and the current England planning summary.

The 2025 reform raised the house-unit limit from 0.6m³ to 1.5m³, allowed two units on a detached house, removed the boundary buffer and admitted systems used for heating and cooling. Cooling-only equipment still does not qualify.

How close can a heat pump be to the boundary?

England’s Class G rules no longer specify a minimum boundary distance. A unit can be less than one metre away and still potentially qualify, but a close position may fail the noise test.

MCS 020 a) Issue 1.1 requires no more than 37 dB(A) at each relevant “assessment position”: one metre outside the centre of a door or window serving a neighbouring habitable room. A habitable room is used for living or sleeping, rather than as a bathroom, hall or utility room.

The installer must assess every position that could be affected, not simply the nearest window. With two pumps, their combined calculated sound is tested. The contractor should retain one completed calculation and give the customer another.

Ask for the calculation before installation and check that it uses the chosen model and location. Passing it addresses sound only; all other planning conditions still apply.

Expert insight

“Removing the boundary buffer shifts attention to the sound path between the unit and neighbouring rooms. A position beside a fence may still fail where a window has clear line of sight.”

Giles Crosse

Energy Editor

Experienced editor, journalist and communications consultant specialising in consumer energy and low carbon technologies.

• Editor and campaign author for Shell, EDF Energy and Good Energy.
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Can you install two heat pumps, or one for a flat?

A detached house can have two units if every other condition is met. The MCS method tests their combined sound. Semi-detached and terraced houses remain limited to one.

For a block of flats, the allowance is one unit for the whole block, not one per flat. An existing communal or individual unit may therefore use the allowance. Other flats in the same block count as neighbouring properties for the sound assessment.

Leaseholders should check the lease and obtain written freeholder or landlord consent where required. This can be necessary even where planning and building-control requirements are met.

Good to know

Planning permission and freeholder consent answer different questions. Securing one does not secure the other.

When will you still need planning permission?

A planning application is likely where a proposal exceeds a Class G limit—for example, because there are too many units, the unit is too large, the sound calculation fails or a pitched-roof position is proposed. Permission may also be needed where an Article 4 direction, planning condition or other restriction has removed the normal right.

Class G does not apply within the curtilage of a listed building or within a scheduled monument. Listed building consent may also be needed where work affects a listed building’s special interest. Historic England says consents are likely in listed buildings and other sensitive historic settings.

A conservation area does not automatically remove the right. However, a unit cannot be on a wall or roof fronting a highway, or nearer a bounding highway than the nearest part of the building. Outside conservation areas and World Heritage Sites, a unit above ground-floor level on a highway-facing wall is excluded.

A planning application is not an automatic refusal; it lets the local planning authority assess a proposal outside the national permission.

Good to know

A proposed lawful development certificate can formally confirm that a specific design is lawful for planning purposes. It does not replace other consents.

What should you check before installation?

1. Identify the property and designation. Confirm whether it is detached, attached, a wholly residential block, listed or in another protected area.

2. Count existing equipment. Include every air source heat pump and check for relevant wind turbines.

3. Check the model and position. Record its volume including housing, plus the roof, highway-facing and heritage limits.

4. Obtain the MCS calculation. Ask the installer to test all relevant neighbouring openings and combined sound where two units are proposed. Keep your copy.

5. Check local and private restrictions. Ask the planning authority about Article 4 directions or conditions, and obtain any lease consent in writing.

6. Consider formal confirmation. Where the position is uncertain, a proposed lawful development certificate may provide useful evidence.

Planning is only one part of the project. Building regulations and any heritage, landlord, freeholder or managing-agent approval must be addressed separately. Technical suitability needs a property-specific assessment.

How do the rules differ elsewhere in the UK?

Planning is devolved, so England’s Class G limits should not be applied across the UK.

Homeowners outside England should use their nation’s legislation and local planning guidance.

Key takeaways

• Every Class G condition must be met for permitted development.

• Detached houses can have two units; other houses and blocks can have one.

• England’s boundary buffer has gone, but the MCS sound test remains.

• The size cap is 1.5m³ for a house and 0.6m³ for a block.

• Heritage, roof, highway-facing and local restrictions can change the answer.

• Planning status does not remove building-control or leasehold-consent requirements.

Frequently asked questions