Lightning protection for solar PV: when it is required and how the risk is calculated

27 October 2026 · 5 min read

Panels on a roof change the situation even where a lightning protection system already exists. Whether protection is required is decided by a risk calculation – and that has clear rules.

Why panels change the situation

A rooftop solar plant is a large metal structure with electronics, connected by cables to the inverter and the switchboard inside the building. For lightning protection this means three things: new highest points have appeared on the roof, a new path for lightning current and surges leads into the building, and the existing lightning protection system – if there is one – no longer matches the state it was designed for. Panels must not be part of the air-termination system and must not lie too close to it.

When lightning protection is required

The answer comes from risk management under EN 62305-2. The calculation compares the risk of loss of human life, or economic loss, with the tolerable value. The calculation takes into account:

the dimensions and shape of the building and its position relative to the surroundings (free-standing, among other buildings),
the lightning ground flash density at the location,
the type of roof and structure, the occupancy of the building and the time people spend in it,
the lines entering the building – the power supply, data cables and, newly, the DC lines from the panels,
existing protection measures.

If the calculated risk exceeds the tolerable value, protection is required, and the calculation also determines the LPS class (I to IV), which decides the mesh size of the air-termination network, the rolling sphere radius and the spacing of the down conductors. The result cannot be guessed in advance from the type of building – two similar buildings can come out differently depending on their position, structure and the lines that enter them. The calculation for the specific building decides; the building authority usually requires it in the documentation.

How lightning protection with PV is designed

Air-termination system

Air-termination rods are placed so that the panels lie within the protected volume – verified by the rolling sphere or the protective angle method. On large flat roofs a mesh system is used, supplemented by rods at the panel arrays. The shadow of the rods on the panels is taken into account in the design; the rods are placed north of the arrays or between the rows so that generation losses are minimal.

Separation distance

Between the lightning protection system and the metal parts of the plant (frames, structure, cables) a separation distance must be kept so that during a strike the lightning does not flash over from the rod into the panels and from there into the building. It is calculated from the LPS class, the length of the current path and the number of down conductors. On roofs with panels it often cannot be kept – then insulated down conductors (HVI) are used, which replace the separation distance with insulation, or the structure is bonded to the lightning protection system and the surge protective devices take over the protection.

Earthing and bonding

The panel structure is bonded and connected to the building's protective bonding; the lightning protection system is earthed to the common earthing system. Whether the two systems are separated or connected follows from the separation distance calculation – it cannot be chosen arbitrarily.

Surge protection

On the AC side, surge protective devices of the appropriate type are designed in the plant switchboard, depending on whether the building is protected by a lightning protection system and whether the separation distance is kept. On the DC side, inverters mostly have surge protection integrated; separate devices are added where the inverter manufacturer or the calculation requires it, for example on longer DC lines.

An existing lightning protection system and new PV

The most common case in practice: a hall or house has a lightning protection system from earlier and panels are being added. The existing system has to be reassessed – new highest points, a new separation distance, often new air-termination rods. After installation, the inspection engineer will require documentation showing that the panels are within the protected volume and that the separation distance is kept or replaced by insulated down conductors. Without it the inspection will fail or carry reservations.

What you get in the design

the risk management calculation with a report and the choice of LPS class,
a roof plan with the air-termination system, down conductors and panel arrays, elevations and details,
the separation distance calculation and the design of insulated down conductors where needed,
earthing, bonding and surge protection,
a technical report and bill of quantities for the installer and the inspection engineer.

We check the air-termination system in 3D on the real shape of the roof. More on the lightning protection page; the links to the plant design are in the article on what a solar PV design includes.

Frequently asked questions

Is surge protection at the panels enough instead of a lightning protection system?

No. Surge protection protects the electronics against overvoltage; the lightning protection system protects the building and the people in it against a direct strike. Whether lightning protection is required is decided by the risk calculation; surge protective devices are its complement, not a substitute.

Can the panels be part of the lightning protection system?

No. Neither the panel frames nor the structure are air-termination devices. Lightning caught by a panel would pass into the inverter and the building's electrical installation.

How is lightning protection handled on a ground-mounted plant?

The risk is calculated for the whole plant; protection is provided by air-termination rods at the arrays or by isolated air-termination masts and an earthing system connected to the structures and the transformer station. For larger plants, protection is usually designed with regard to economic loss, not only to people.

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