Here's what you need to know — and the timelines to expect.
Permitted development for commercial solar
Under the Town and Country Planning (General Permitted Development) Order, solar panels on commercial buildings generally fall under Class J permitted development rights, provided:
- Panels must not protrude more than 200mm beyond the plane of the roof
- The building must not be in a conservation area, World Heritage Site, or National Park
- The building must not be listed
- Panels should be sited to minimise effect on external appearance
- Panels must be removed when no longer needed
2023 expansion
When you DO need planning permission
- The building is listed (listed building consent required)
- The site is in a conservation area, National Park, AONB, or World Heritage Site
- The system protrudes more than 200mm beyond the roof plane
- Ground-mounted systems above local thresholds
- The LPA has removed permitted development rights via an Article 4 Direction
If in doubt, a pre-application enquiry to your LPA takes 3–8 weeks and gives written indication of whether your scheme needs consent.
Large-scale commercial solar: separate considerations
Very large installations — typically above 1MW — may require Environmental Impact Assessment (EIA) screening, particularly on greenfield land. Ground-mounted solar farms have their own planning framework. For rooftop systems below 1MW on standard industrial or commercial buildings, permitted development almost always applies in England. Scotland and Wales have slightly different rules.
Building regulations and DNO requirements
- Building Regulations Part P: all electrical work must comply. NICEIC-approved contractors self-certify — no local authority inspection needed.
- G99 application: systems above 16A per phase (~3.68kW) require DNO notification. Larger systems require a full G99 application — we handle it.
- Structural assessment: flat roofs must be assessed for load-bearing capacity.
- Fire safety: panel layout must comply with fire access and compartmentalisation requirements on larger industrial rooftops.
We'll confirm planning status on day one
Free planning assessment as part of every commercial enquiry.
Timelines: what to expect
| Requirement | Typical timeline | Who handles it? |
|---|---|---|
| Permitted development (no application) | Immediate — no approval needed | N/A |
| G98 notification (smaller systems) | Notice only — no delay | Alliant |
| G99 application (larger systems) | 10–25 working days | Alliant |
| Full planning application | 8–13 weeks | Alliant + planning consultant |
| Listed building consent | 8–13 weeks (often longer) | Alliant + heritage consultant |
For most commercial installations, the DNO G99 application is the critical path item. We submit this as soon as you confirm — and we have not had a commercial G99 application refused.
Frequently asked questions
Do I need planning permission for solar panels on a commercial flat roof?
In most cases no. Flat-roof commercial solar on standard industrial buildings in England falls under permitted development, provided the system doesn't protrude more than 200mm and the building isn't listed or in a protected area.
What about a commercial building in a conservation area?
Conservation area status may restrict permitted development rights. In practice, rear or roof-mounted installations not visible from the street are often approved, but a pre-application enquiry to the LPA is advisable.
Will solar panels affect our commercial building insurance?
You should notify your insurer — it's a material change to the property. Most commercial insurers cover solar as a standard building fixture with no significant premium change. NICEIC-certified installations are generally unproblematic.
