Solar PV Electrical Requirements for Electricians

Why Electricians Need to Understand Solar PV

Solar PV installations have surged across the UK, and the electrical work involved goes well beyond bolting panels to a roof. Whether you're installing a full system, adding battery storage, or simply connecting a PV array to an existing consumer unit, you need to understand the specific regulations that govern this work.

Getting it wrong doesn't just risk a failed inspection — it can create genuine fire hazards, electrocution risks, and leave homeowners with systems that their DNO hasn't been notified about. This guide covers the key electrical requirements you need to know for domestic solar PV work in 2026 and beyond.

Applicable Standards and Regulations

Solar PV electrical installations in the UK fall under several overlapping standards:

• BS 7671 (IET Wiring Regulations, 18th Edition) — the foundation for all electrical installation work, including Section 712 specifically covering solar PV supply systems
• IET Code of Practice for Grid-Connected Solar PV Systems — the go-to supplementary guidance document
• Engineering Recommendation G98 (formerly G83) — governs the connection of small-scale embedded generators up to 16A per phase to the distribution network
• Engineering Recommendation G99 — applies to larger installations above 16A per phase (less common on domestic jobs but worth knowing)
• Building Regulations Part P — solar PV electrical work is notifiable under Part P in England and Wales
• MCS (Microgeneration Certification Scheme) — required for the homeowner to access the Smart Export Guarantee (SEG) payments

DC Side Requirements

The DC side of a solar PV installation is where most of the PV-specific requirements apply, and where mistakes are most dangerous.

DC Isolators

You must install a DC isolator switch between the PV array and the inverter. Key requirements include:

• The isolator must be rated for DC use — never use an AC-rated isolator on a DC circuit. DC arcs don't self-extinguish at zero-crossing like AC arcs do, so DC-rated devices have arc-quenching mechanisms designed for the job.
• The isolator must be rated for the maximum open-circuit voltage (Voc) of the string at the lowest expected temperature (use the temperature correction factors from the module datasheet, typically calculated at -15°C for the UK).
• Rooftop DC isolators were once standard practice but have become controversial due to water ingress and fire risk. The IET Code of Practice now permits omitting the rooftop isolator where a risk assessment supports it and the inverter provides equivalent isolation. Check the latest edition of the Code of Practice and your MCS requirements before deciding.
• A DC isolator adjacent to the inverter remains mandatory.

DC Cable Selection and Routing

DC cables from the PV array carry current whenever there is daylight — you cannot simply switch them off. This has major implications:

• Use double-insulated PV-specific cable (typically rated to 1500V DC) with UV-resistant sheathing for any external runs.
• Keep positive and negative conductors close together to minimise the loop area and reduce induced voltages. Ideally, use twin-core PV cable or route them in the same conduit/trunking.
• Avoid running DC cables through occupied spaces wherever possible. Where this is unavoidable, use metal conduit or trunking to provide additional fire protection. BS 7671 Section 712.52 covers this requirement.
• Cable sizing must account for voltage drop, current-carrying capacity, and the specific installation method. The Voc and Isc figures from the module datasheets (temperature-corrected) are your starting point.

AC Side Requirements

The AC connection from the inverter to the consumer unit must comply with standard BS 7671 requirements, plus some PV-specific additions.

Connection to the Consumer Unit

• The inverter AC output should be connected via a dedicated circuit with its own MCB in the consumer unit.
• The MCB must be positioned so that the total load on the busbar doesn't exceed the busbar rating. Good practice (per the IET Code of Practice) is to connect the PV supply at the opposite end of the busbar from the main incoming supply, or to confirm by calculation that the busbar won't be overloaded.
• If the existing consumer unit doesn't have a spare way in a suitable position, you may need to install a separate enclosure for the PV circuit with its own RCD protection.
• An AC isolator must be installed between the inverter and the point of connection to allow the PV system to be isolated from the supply.

RCD Protection

The PV AC circuit will usually need 30mA RCD protection (for example, where cables are concealed in walls). Just as important is the type of RCD:

• Many inverters can produce DC fault currents on the AC side. A Type A RCD may not detect these. Where the inverter does not have built-in DC fault current detection, a Type B RCD is required on the AC circuit.
• Check the inverter manufacturer's documentation — most modern inverters include internal DC fault current monitoring, which allows a Type A RCD to be used. Don't assume; verify.

G98 Notification (Formerly G83)

For domestic PV installations up to 16A per phase (which covers the vast majority of residential systems up to around 3.68kW single-phase), you must notify the Distribution Network Operator (DNO) using the G98 process.

• G98 is a notification process, not an application for permission. You notify the DNO within 28 days of commissioning using the standard G98 form.
• For systems between 3.68kW and 50kW on a single-phase supply, you'll need to apply under G99, which requires DNO approval before connection. This is increasingly relevant as homeowners request larger systems with battery storage.
• The installer (not the homeowner) is responsible for making the notification.
• Most DNOs now accept notifications through the ENA's online portal.

Labelling Requirements

Solar PV installations require specific warning labels beyond the standard circuit identification. BS 7671 Section 712.514 requires:

• A label at the point of connection to the electrical installation (consumer unit) warning that the system includes a dual supply.
• A label at the main isolator warning that the PV system may still be live even when the mains supply is isolated.
• Labels at all DC junction boxes and isolators identifying them as PV DC circuits.
• A fireman's switch label if required (typically on commercial installations, but check local fire authority requirements).

Use durable, engraved labels — printed adhesive labels that fade and peel off within two years aren't acceptable for permanent installations.

Certification and Paperwork

A domestic solar PV installation requires:

• BS 7671 Electrical Installation Certificate (EIC) — covering all the electrical work. This is a notifiable job under Part P, so you either need to be registered with a competent person scheme (NAPIT, NICEIC, etc.) or notify Building Control.
• MCS Certificate — if the homeowner wants access to the Smart Export Guarantee. Only MCS-certified installers can issue this.
• G98/G99 notification confirmation — proof of DNO notification.
• Commissioning records — including inverter settings, string voltages, insulation resistance, and earth fault loop impedance readings.
• Handover pack — operation and maintenance instructions, datasheets, and warranty information for the homeowner.

Common Mistakes to Avoid

• Using AC-rated isolators on DC circuits — this is a fire risk, full stop.
• Undersizing DC cable — failing to apply temperature correction factors to Voc and Isc values.
• Incorrect RCD type — not checking whether the inverter requires Type B RCD protection.
• Missing DNO notification — creates problems for the homeowner and reflects badly on you.
• Inadequate labelling — every access point to a PV circuit must be clearly identified as a dual supply.
• Running DC cables through occupied spaces without protection — a fire safety issue that inspection will catch.

Further Reading

For detailed guidance, consult these resources:

• BS 7671 IET Wiring Regulations (18th Edition)
• IET Code of Practice for Grid-Connected Solar Photovoltaic Systems
• ENA Engineering Recommendations G98 and G99
• MCS Certification Scheme

Published 2026-07-06. This article is for general guidance only and does not constitute legal or professional advice. Always refer to the relevant standards and consult qualified professionals for definitive requirements.