UK solar PV compliance covers more regulatory layers than most installers expect. A single residential installation touches grid connection standards (G98 or G99), MCS certification, BS 7671 wiring regulations, planning rules, and the Smart Export Guarantee — each governed by a different authority.
This guide provides a complete overview of UK solar compliance for installers, designers, and solar companies operating in England, Scotland, and Wales.
The UK Solar Compliance Framework
UK solar compliance operates through five parallel regulatory systems that all apply to the same installation:
| Requirement | Standard | Authority | Who Enforces |
|---|---|---|---|
| Grid connection | G98 / G99 | ENA Engineering Recommendation | Distribution Network Operator (DNO) |
| Electrical installation | BS 7671 | IET Wiring Regulations | Building control / Part P |
| Installer qualification | MCS (for SEG) | Microgeneration Certification Scheme | MCS administrator |
| Export payments | Smart Export Guarantee | Ofgem | Licensed electricity suppliers |
| Planning | Permitted development / full permission | Local planning authority | Local council |
Every installation must satisfy all five. An installation that is G98-compliant but not MCS-certified can still be legally connected — it just cannot access SEG payments.
G98 and G99: Grid Connection Standards
The G98 and G99 Engineering Recommendations are published by the Energy Networks Association and specify the technical and administrative requirements for connecting generating plant to the low-voltage (LV) distribution network.
The key threshold is 16 amps per phase:
| System Type | Export Current | Standard | Process |
|---|---|---|---|
| Single-phase up to 3.68 kW | Up to 16A | G98 | Fit-and-inform (28-day notification) |
| Three-phase up to 11 kW | Up to 16A/phase | G98 | Fit-and-inform (28-day notification) |
| Single-phase above 3.68 kW | Over 16A | G99 | Pre-approval required (45 working days) |
| Three-phase above 11 kW | Over 16A/phase | G99 | Pre-approval required (45 working days) |
The combined capacity rule also applies: if adding a new generator would push the total site generation capacity above the 16A/phase threshold when combined with existing generators on the same connection, G99 applies regardless of the new system’s size in isolation.
G100 is a separate standard that applies specifically to DC-coupled battery storage systems and governs how they export to the grid. If your project includes batteries, confirm whether G100 applies alongside G98 or G99.
G98 vs G99 in Practice
Most residential solar PV systems in the UK — typically 3–6 kW on a single-phase connection — fall under G98. The fit-and-inform process means the installer notifies the DNO after commissioning, and the system can operate immediately unless the DNO objects within 28 days. G99 is more common for commercial systems, large residential installs, or any system that exports at more than 16A per phase.
For a full technical breakdown of the 16A calculation, protection settings, and per-DNO differences, see the G98 vs G99 guide.
MCS Certification
MCS (Microgeneration Certification Scheme) is the quality standard for small-scale renewable energy in the UK. MCS certification covers both the installing company and the products they install.
To qualify for the Smart Export Guarantee, the installation must be:
- Carried out by an MCS-certified installer
- Using MCS-certified products (panels, inverter, mounting system)
- Documented with an MCS certificate issued to the customer
MCS certification is not legally mandatory for the physical installation itself — a non-MCS installer can legally connect solar panels to a house. But without MCS, the customer loses access to SEG payments, which are the primary financial return mechanism for residential solar in the UK since the Feed-in Tariff closed in 2019.
The full MCS certification process, audit requirements, and cost is covered in the MCS Certification guide.
Smart Export Guarantee (SEG)
The Smart Export Guarantee replaced the Feed-in Tariff export element in January 2020. Under SEG, Ofgem requires all licensed electricity suppliers with 150,000 or more domestic customers to offer at least one SEG tariff for exported solar electricity.
Key SEG rules:
- System must be 5 MW or less (all residential and most commercial systems qualify)
- Installer and products must be MCS-certified
- Customer must have a smart meter that can record half-hourly export data
- Tariff rate must be above zero — suppliers compete on rate
SEG rates vary significantly by supplier and tariff type. Some tariffs pay a fixed p/kWh rate; others pay a variable rate linked to wholesale prices. The SEG Tariff Comparison tool tracks current rates across major suppliers.
Full SEG eligibility, registration steps, and tariff comparison guidance is in the Smart Export Guarantee guide.
BS 7671: Wiring Regulations
All electrical work on a UK solar PV installation must comply with BS 7671 (IET Wiring Regulations), currently the 18th Edition with Amendment 2 (published 2022).
Solar-specific requirements are in Part 7, Section 712 of BS 7671. Key requirements:
- DC isolators at the array, inverter input, and any battery connections
- Correct cable sizing for DC circuits (different methodology from AC)
- Surge protection devices where risk of overvoltage exists
- Arc fault detection considerations for DC string circuits
- Correct earthing arrangements for the PV array and inverter
A qualified electrician must carry out the installation and issue an Electrical Installation Certificate on completion. In England and Wales, solar PV work falls under Part P of the Building Regulations — this can be self-certified by a registered competent person scheme member (NICEIC, NAPIT, or equivalent).
Full BS 7671 requirements for solar are in the BS 7671 Solar guide.
Distribution Network Operators (DNOs)
The UK has six Distribution Network Operators, each responsible for a specific geographic area. All G98 notifications and G99 applications go directly to the local DNO.
| DNO | Area Covered |
|---|---|
| UK Power Networks (UKPN) | London, South East, East of England |
| National Grid Electricity Distribution (NGED) | Midlands, South West, South Wales |
| Northern Powergrid | North East England, Yorkshire |
| Electricity North West (ENW) | North West England |
| SP Energy Networks (SPEN) | Scotland, North Wales |
| SSE Networks | Scottish Highlands, Southern England |
Each DNO has its own online portal, application forms, and processing timelines. UKPN and NGED have well-developed online portals; Northern Powergrid and ENW still rely on email-based submission for some application types. The per-DNO guides below cover the specific process for each one.
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Planning and Permitted Development
In England and Wales, solar panels on a dwelling are generally permitted development — no planning permission is needed — provided:
- Panels do not protrude more than 200mm from the roof surface
- The installation is not on a listed building
- The site is not in a World Heritage Site (where additional restrictions apply)
- Total capacity after installation remains below specified thresholds
Conservation area properties can install solar on non-street-facing roof slopes without consent. Street-facing slopes in conservation areas require a planning application.
Scotland has similar permitted development rules under the Town and Country Planning (General Permitted Development) (Scotland) Order. Wales follows its own provisions under the Town and Country Planning (General Permitted Development) Order 1995 as amended.
Commercial and non-domestic buildings have different thresholds and may require planning permission even for relatively small systems. Full guidance is in the Permitted Development Rights guide.
Regional Differences
UK solar compliance is mostly uniform at the technical standard level (G98/G99, BS 7671, MCS apply equally across Great Britain), but some regional differences exist:
England: Standard permitted development rules apply. Part P of the Building Regulations requires competent person scheme registration or building control notification for electrical work.
Scotland: Building Standards (equivalent to Building Regulations in England/Wales) have slightly different requirements. Scottish Government has its own planning guidance for renewable energy. SPEN and SSE are the relevant DNOs.
Wales: Wales follows its own planning policy on renewable energy. NGED covers most of Wales. The Welsh Government has separate policy statements on permitted development for solar.
Regional pages for England, Scotland, and Wales cover the specific differences in detail.
UK Solar Compliance and Design Software
Producing compliant G98/G99 documentation, BS 7671-compliant single-line diagrams, and MCS project records manually is time-intensive. Solar design software that integrates UK standards can generate these documents automatically from the system design.
Good solar software for UK compliance should output:
- G98 notification pack (system specs, inverter data, protection settings)
- G99 application documentation (single-line diagram, protection relay schedule, export limitation details)
- MCS-compatible project record with all required fields
- BS 7671 Section 712 installation schedule
See the Solar Design Software UK comparison for a full review of available tools.
All UK Solar Compliance Pages
Frequently Asked Questions
What is the difference between G98 and G99?
G98 applies to systems that export 16A or less per phase — typically residential solar up to 3.68 kW single-phase. It uses a fit-and-inform process where the installer notifies the DNO after commissioning and the system can operate unless the DNO objects within 28 days. G99 applies to larger systems and requires formal DNO pre-approval before installation, with a 45 working day review period.
Do I need MCS certification to install solar in the UK?
MCS is required if the customer wants Smart Export Guarantee payments. Without MCS, the physical installation can still be completed and connected legally, but the owner cannot claim SEG export tariff payments. MCS certification covers both the installing company and the specific products used.
What is the Smart Export Guarantee?
The SEG is the UK’s main solar export payment scheme, replacing the Feed-in Tariff export element from January 2020. Ofgem requires large licensed suppliers to offer export tariffs above zero p/kWh. Customers must be MCS-certified and have a smart meter. Rates vary by supplier.
Which DNO covers my project?
The UK has six DNOs. UK Power Networks covers London, South East, and East of England. NGED covers the Midlands, South West, and South Wales. Northern Powergrid covers North East England and Yorkshire. Electricity North West covers North West England. SP Energy Networks covers Scotland and North Wales. SSE Networks covers the Scottish Highlands and Southern England.
Do I need planning permission for solar in the UK?
Most residential solar is permitted development in England and Wales — no planning permission needed — provided the panels don’t protrude more than 200mm from the roof surface and the property isn’t listed. Conservation areas allow solar on non-street-facing slopes. Listed buildings require a planning application.
