Commercial Solar PV Compliance UK
The full commercial solar PV compliance stack — MCS certification, G99 grid connection, BS 7671 18th Edition, CDM 2015, Building Regulations Part A, and planning — explained for UK businesses.
Commercial solar PV is one of the most heavily regulated areas of UK construction. Every installation crosses electrical standards, grid code, structural engineering, health and safety law, and frequently planning. This guide sets out the six compliance areas every UK commercial solar PV project must satisfy.
Quick Answer
What compliance is required for a commercial solar PV installation in the UK?
UK commercial solar PV must satisfy six compliance areas: MCS contractor certification with MCS design sign-off; a G99 (or G98 for small systems) grid connection agreement from your DNO; BS 7671 18th Edition electrical compliance; structural calculations to BS EN 1991; CDM 2015 principal designer and contractor duties; and Building Regulations Part A sign-off. Planning permission is usually not required (permitted development) but applies to listed buildings, conservation areas, and ground-mount over 1MW.
MCS Certification & Design Sign-off
The Microgeneration Certification Scheme (MCS) certifies both the products and the installer. For commercial solar PV, the installing contractor should hold MCS contractor certification and provide an MCS-registered design sign-off. MCS is not legally mandatory, but it is required to access most grants, the Smart Export Guarantee (SEG), and is expected by most insurers and asset-finance lenders. An MCS certificate is issued on commissioning and is the document your finance provider and SEG supplier will ask for.
G99 / G98 Grid Connection (DNO)
Any system that can export to the grid needs a connection agreement from your Distribution Network Operator (DNO). Systems exporting more than 16A per phase (about 3.68kW single-phase or 11kW three-phase) require a G99 application, assessed over a standard 65 working days. Smaller systems use the simpler G98 notification. A G99-compliant interface protection relay must be fitted. Where the local network is constrained, a zero-export (G100) limitation device allows the project to proceed without grid reinforcement. See our DNO connection guide.
BS 7671 18th Edition Electrical Compliance
All fixed electrical work, including the DC and AC sides of a solar PV array, must comply with BS 7671 (the IET Wiring Regulations, 18th Edition) plus IEC 62446 for PV-specific testing and commissioning. This covers cable sizing, DC isolation, surge protection, earthing and bonding, and the labelling and documentation handed over at commissioning. Work should be certified by a competent person and is the basis of the electrical installation certificate (EIC) you receive.
Structural Calculations to BS EN 1991
Mounting solar on a commercial roof adds dead load, wind uplift, and (for ballasted systems) significant point loads. Structural calculations to BS EN 1991 (Eurocode 1) must confirm the roof can carry the array under wind and snow loading. For older or lightweight roofs, this may dictate a non-penetrating lightweight mounting system or, occasionally, structural strengthening. Building Regulations Part A (structure) governs this and requires the calculations before installation.
CDM 2015 & Health and Safety
Commercial solar installation is construction work under the Construction (Design and Management) Regulations 2015. The project needs a named principal designer and principal contractor, a construction phase plan, and (on larger jobs) F10 notification to the HSE. Working at height on commercial roofs is the dominant risk. The single most common cause of UK commercial solar project failure is fragmented delivery — multiple subcontractors with no single point of accountability — so deliver the project as one principal contract.
Planning Permission & Building Regulations
Most commercial rooftop solar is permitted development and needs no planning application. Exceptions: listed buildings, conservation areas, Article 2(3) land, and ground-mounted arrays (especially over 1MW, which need full planning). Building Regulations Part A always applies (structure); Part P applies where there is a residential element. We confirm the planning position for your site as part of the free survey.
Cost & Economics
UK commercial solar PV costs £0.75–£1.05 per watt installed in 2026 (see the full commercial solar cost guide). Most projects pay back in 4–7 years on capital purchase. The Annual Investment Allowance gives UK limited companies 100% first-year capital deduction — effectively 19–25% tax relief in year one. The Public Sector Decarbonisation Scheme covers up to 100% of capital for public sector estates. See commercial solar grants.
Related Compliance Resources
Frequently Asked Questions
Do I need G99 or G98 for a commercial solar installation?
Commercial systems exporting more than 16A per phase (about 3.68kW single-phase or 11kW three-phase) require a G99 connection agreement from your DNO, assessed over roughly 65 working days. Smaller systems use the simpler G98 notification. Where the local grid is constrained, a G100 zero-export device lets the project proceed without reinforcement, capping export at zero while you still self-consume on site.
Is MCS certification mandatory for commercial solar?
MCS is not legally mandatory, but it is effectively required in practice: it is needed to access most grants, to register for the Smart Export Guarantee, and is expected by most insurers and asset-finance lenders. The installing contractor should hold MCS contractor certification and provide an MCS-registered design sign-off, with the MCS certificate issued on commissioning.
What building regulations apply to commercial rooftop solar?
Building Regulations Part A (structure) always applies — it governs roof loading and requires structural calculations to BS EN 1991 confirming the roof can carry the array under wind and snow loads. Part P applies where there is a residential element. The electrical work must comply with BS 7671 18th Edition plus IEC 62446 for PV testing and commissioning.
Does commercial solar need planning permission?
Most commercial rooftop solar is permitted development and needs no planning application. Exceptions are listed buildings, conservation areas, Article 2(3) land, and ground-mounted arrays — particularly those over 1MW, which require full planning permission. We confirm the planning position for your specific site as part of the free feasibility survey.
Who is responsible for health and safety on a commercial solar project?
Commercial solar installation is construction work under CDM 2015, so the project must have a named principal designer and principal contractor, a construction phase plan, and F10 notification to the HSE on larger jobs. Delivering the project as a single principal contract — rather than fragmented subcontracts — ensures one point of accountability and is the best protection against the most common cause of project failure.
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