Heat Pump Permitted Development 2026: How AI-Assisted Siting Gets You Under MCS 020
🔍 Key takeaways
- From 28 May 2026, MCS 020a is the only certification scheme accepted for heat pump permitted development in England.
- MCS 020 caps outdoor-unit noise at 42 dB(A), measured 1 metre from a neighbour’s habitable room window.
- England scrapped the one-metre boundary rule in 2025 and raised the unit size limit to 1.5 cubic metres.
- AI-assisted siting lets installers test the unit’s position against the noise limit before quoting the job.
- A failed noise assessment forces a full planning application: eight weeks and a £258 fee in England.
What changes for heat pump permitted development in England in 2026?
From 28 May 2026, MCS 020a becomes the only certification scheme England accepts for air source heat pumps installed under permitted development, and the previous ‘equivalent standard’ route closes. MCS 020a has been mandatory for every permitted development install since 20 September 2025. Compliance is no longer optional paperwork, it is the gate to skipping planning permission.
| Condition | Before 29 May 2025 | From 29 May 2025 |
|---|---|---|
| Distance from boundary | Minimum 1 metre | No minimum distance |
| Max outdoor unit volume (house) | 0.6 m³ | 1.5 m³ |
| Units per detached house | One | Up to two |
| Air-to-air (cooling) units | Excluded | Included |
| Noise certification | Equivalent schemes allowed | MCS 020a only (from 28 May 2026) |
What is MCS 020, and how does the noise calculation work?
MCS 020 is the MCS planning standard that predicts how loud an air source heat pump will be at the nearest neighbour’s window. The installer takes the manufacturer’s declared sound power level, applies corrections for distance, reflections and barriers, and calculates the sound pressure level one metre from the centre of the nearest neighbour’s habitable room window. The threshold is fixed: 42 dB(A) or below qualifies for permitted development; anything higher needs a full planning application.
Which siting conditions decide whether an installation qualifies for permitted development?
- Outdoor unit size: The compressor unit must not exceed 1.5 cubic metres on a house or 0.6 cubic metres on a block of flats.
- Number of units: Detached houses may have up to two units; semi-detached, terraced homes and flats are limited to one.
- Position in conservation areas: The unit must not sit on a wall or roof fronting a highway.
- Listed buildings: Permitted development does not apply. The job needs planning permission and listed building consent.
- Siting for amenity: Units must be positioned to minimise their effect on the amenity of the area.
How does AI-assisted siting help installers pass MCS 020?
AI-assisted siting lets installers test a unit’s position against the 42 dB(A) limit before anyone visits the property. autarc’s installation simulation places the outdoor unit against the property and the nearest habitable window, then tests distances and barriers against the MCS 020 threshold.
- Capture the property: A digital model or scan records the building, boundaries and the neighbour’s nearest habitable window.
- Place the unit: The installer positions the outdoor unit and any acoustic barrier in the model.
- Run MCS 020: The software calculates the predicted sound pressure level and flags whether it clears 42 dB(A).
- Decide the route: A pass confirms permitted development; a fail signals a full planning application before the quote goes out.
What happens when a heat pump can’t meet MCS 020 under permitted development?
| Route | When it applies | Fee | Timeline |
|---|---|---|---|
| Permitted development | MCS 020 pass and all conditions met | No planning fee | Immediate |
| Full planning application | Noise above 42 dB(A) or a condition breached | £258 | 8 weeks+ |
| Planning + listed building consent | Listed building | £200–£500 | 8–12 weeks |
Conclusion: The noise number now decides the job
From 28 May 2026, MCS 020a is the single gate to permitted development for heat pumps in England. Installers who model the noise before the site visit protect both their timelines and their margins.
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💬 FAQs
Does MCS 020 apply to heat pumps in Scotland and Wales?
No, MCS 020 governs permitted development in England only. Scotland and Wales set their own planning rules.
Do ground source heat pumps need an MCS 020 assessment?
No, MCS 020a covers air source heat pumps only. Ground source systems have no external compressor unit of the same kind.
Does a garden fence or wall count as a barrier in MCS 020?
It can, if it sits between the unit and the neighbour’s window and meets the standard’s requirements. A solid barrier lowers the predicted sound pressure level.
Is a second heat pump on a detached house always permitted development?
Not automatically. Both units must still meet every condition — including the noise assessment and the 1.5 cubic metre size limit.
What records should installers keep for an MCS 020 assessment?
The completed sound calculation, the manufacturer’s sound power data, and the siting details used. These evidence permitted development compliance if an MCS audit queries the installation.
How long does a full planning application take if MCS 020 fails?
In England, a householder application carries a statutory eight-week decision period, though many authorities take 8 to 13 weeks in practice.
References
- MCS 020 Now Mandatory for Heat Pump Planning – UKEM Group, accessed 29 July 2026, https://www.ukem.co.uk/heat-pumps/news/mcs-020-heat-pump-planning-standard/
- New Permitted Development rules in England – MCS, accessed 29 July 2026, https://mcscertified.com/new-permitted-development-rules-in-england-air-source-heat-pump-installations-must-now-comply-with-mcs-020-a/
- New UK planning rules for heat pumps come into effect – pv magazine, 2025, https://www.pv-magazine.com/2025/05/29/new-uk-planning-rules-for-heat-pumps-come-into-effect-one-meter-rule-scrapped/
- Planning Permission: Air source heat pump – Planning Portal, accessed 29 July 2026, https://www.planningportal.co.uk/permission/common-projects/heat-pumps/planning-permission-air-source-heat-pump/