How a commercial solar install works.
From the first look at your bills to the day it switches on: roof checks, planning, the grid, certification and sign-off, step by step.
Over 50kW? You don’t need MCS →Site assessment.
Good systems start with how your site uses power, not how many panels fit on the roof.
- Your usage. Your last 12 months of bills, or half-hourly data if you have it, so the system matches when you use power.
- The roof or land. Size, direction, shading, and roughly how old the roof is.
- The local grid. How much the network can take, and whether an export limit is likely.
- Your site. Whether you own it, or how long is left on your lease.
Roof and structure.
Panels sit on a roof for 25 years or more, so the roof has to be up to it.
- Structural check. A structural engineer confirms the roof can carry the panels and the wind load.
- Asbestos survey. Older roofs are checked before anyone drills or walks on them.
- Roof condition. One recent survey found around a third of commercial roofs needed some repair before solar could go on. Better to know now than after the panels are up.
System design.
Sized for self-consumption first: power you use yourself is worth far more than power you export.
- Panel layout and yield, modelled for your roof or land.
- Inverters and cabling to suit the building and your electrical supply.
- Batteries, where they help you use more of your own power.
- Fire safety designed in from the start, following RC62, the guidance insurers use. See commercial solar fire safety.
More detail: how a commercial solar system is designed.
Do you need planning permission?
Often not for a roof. Usually yes for a field. These are the rules in England; Wales and Scotland have their own, and we check for your site.
Rooftop solar on business and farm buildings
Most rooftop solar on non-domestic buildings is permitted development, so no full planning application is needed. There is no size limit: the old 1MW cap was removed in December 2023.
- Up to 50kW: usually no application at all.
- Over 50kW: you must apply to the local planning authority for prior approval before work starts. It looks at the design and appearance, especially glare for neighbours.
- The local planning authority has 56 days to decide. If it doesn't, work can go ahead.
Limits that still apply
- On a pitched roof, panels can't stick out more than 0.2 metres.
- On a flat roof, they can't be more than 1 metre above the highest part of the roof.
- They must be at least 1 metre from the edge of the roof.
- Permitted development doesn't apply to listed buildings, buildings in their grounds, or scheduled monuments. Those need full permission.
Ground-mount solar
Stand-alone panels at a business or farm can only go in without permission up to 9 square metres, about four panels. Anything bigger needs full planning permission. Local planning authorities aim to decide smaller sites in 8 weeks, and sites of 1 hectare or more in 13 weeks.
Our in-house Chartered Town Planner (MRTPI) handles all of this. See our fixed planning fees and the guide to small ground-mount planning.
Grid connection: G99.
Your network operator has to agree before a commercial system is connected.
- G98 covers only very small systems: up to 16 amps per phase, about 3.68kW single phase or 11kW three phase.
- G99 covers everything bigger, so almost every commercial system needs a G99 application.
- The network operator may set an export limit if the local grid is busy. The system can still run at full power for your own use.
- It can take a while, so we apply early, before any work starts.
More on the grid: grid consultancy.
MCS, and why it stops at 50kW.
MCS is the certification scheme for small renewable systems. It covers solar up to 50kW.
- Up to 50kW: to get Smart Export Guarantee (SEG) payments, the system and the installer need MCS certification, or an equivalent.
- Over 50kW: MCS doesn't apply. For SEG payments, up to 5MW, the installation must be certified to a recognised standard, but the installer doesn't have to be. Your energy supplier decides how it checks this.
What matters for a large system is the paperwork below: G99 approval, a BS 7671 electrical certificate, structural sign-off and good fire safety design.
Building Control and safety.
- Building Control. Fixing panels to a roof is usually building work, so it is notified and signed off under the Building Regulations.
- CDM 2015. Health and safety planned and managed under the Construction (Design and Management) Regulations.
- Working at height. Scaffold or edge protection, and safe access planned before work starts.
Installation.
Installs delivered with certified partner installers. We manage the job and stay your single point of contact.
- Work planned around your business, to keep disruption low.
- Mounting, panels, cabling, inverters and any battery fitted to the agreed design.
- Fire isolation points and clear labels, so firefighters can make the system safe.
Commissioning and handover.
Tested, certified and signed off before it is handed over.
- BS 7671 certificate. An Electrical Installation Certificate to the UK wiring regulations.
- G99 commissioning. Tests sent to the network operator, with any export limit set and tested.
- Building Control sign-off.
- Export payments. Registered with an energy supplier, so you are paid for power you export.
- Your handover pack. Drawings, test results, manuals and warranties, in writing.
Aftercare.
- Monitoring, so you can see what the system is making and spot problems early.
- Maintenance with partners if you want it: inspections, electrical testing and cleaning.
Comparing quotes? Use our installer checklist.
Installation questions
Does commercial solar over 50kW need MCS?
No. MCS covers systems up to 50kW. Over 50kW, to get Smart Export Guarantee payments the installation must be certified to a recognised standard, and your energy supplier decides how to check it. It still needs G99 approval and a BS 7671 certificate.
Do I need planning permission for solar panels on a commercial roof?
In England, usually not. Rooftop solar on non-domestic buildings is permitted development with no size limit. Over 50kW you must apply to the local planning authority for prior approval first. Listed buildings and scheduled monuments need full permission.
How long does prior approval take?
The local planning authority has 56 days to decide. If it has not decided by then, the work can go ahead.
Do I need permission from the network operator?
Yes. Almost every commercial system needs a G99 application to the network operator before it is connected. We handle this for you.
Do ground-mounted solar panels need planning permission?
Usually, yes. At a business or farm, stand-alone panels only avoid planning permission up to 9 square metres. Anything bigger needs a full application.
Ready to get started?
Send us your site postcode and a rough yearly bill. We'll come back within one working day.