Surge protection shields a solar system from brief, high voltage spikes – usually from distant lightning strikes or switching events on the grid that spread through the wiring. Specialist companies use surge arresters on both the DC and AC side for this. Whether and to what extent it's needed depends on the building; that assessment is part of the electrical planning and isn't decided by a blanket rule in a brochure. (As of: July 2026)
Key points in brief
- Surge protection and lightning protection are not the same thing: external lightning protection catches a direct strike, internal surge protection shields the electronics from the voltage spikes.
- What's usually dangerous isn't a direct hit but indirect surges that propagate into the house via the wiring.
- The inverter and connected devices are particularly sensitive – a surge can damage them.
- Arresters are fitted on the DC and the AC side; which combination makes sense follows from the electrical planning.
- Whether surge protection is mandatory or just recommended depends on the building and any existing external lightning protection – the specialist company clarifies this.
What is surge protection – and what does it do?
Surge protection limits brief, very high voltage spikes before they reach the system's electronics. Such spikes last only fractions of a second but sit far above normal operating voltage – and that's exactly what damages sensitive components.
The most common cause isn't a direct lightning strike but indirect surges. When lightning strikes nearby or larger switching events occur on the grid, voltage spikes arise that spread through power and data lines. They reach the house, and the system, this way even without the building itself being hit.
The protection consists of surge arresters. These are components that do nothing during normal operation and, in a fraction of a second during a spike, open a path that diverts the energy away – to earth, away from the electronics. Afterwards they close again. Think of them like a valve that only briefly opens under excess pressure.
Why is a solar system particularly at risk?
Because it brings together two things that attract and channel surges: a large area on the roof and long cable runs across the building.
The modules sit exposed at the highest point of the house. From there, DC cables run to the inverter, and from there onward into the house wiring. This route acts as a kind of antenna for voltage spikes from the surroundings – and at the end sits the inverter, the system's most sensitive and expensive active component.
If a surge hits the inverter, in the worst case it's destroyed; connected devices in the house often suffer too. Exactly how electricity travels from the modules into the house distribution board, and which protective devices come into play there, is shown in the article on the electrics of a solar system. This article here goes deeper into one building block: protection against surges.
What's the difference between internal and external lightning protection?
The two systems handle different jobs and are often confused.
External lightning protection – the classic lightning protection system with air-termination and down conductors on the façade – catches a direct strike and channels its energy into the ground in a controlled way. Whether a building has external lightning protection at all depends on its type, height and use; many single-family homes don't have one.
Internal surge protection deals with the voltage spikes on the wiring – regardless of whether the house was hit directly. It sits at the transfer points in the system and protects the electronics.
| External lightning protection | Internal surge protection | |
|---|---|---|
| Protects against | a direct lightning strike | voltage spikes on the wiring |
| Where | Roof & façade (air termination, down conductors) | in the electrical installation (arresters) |
| Typical trigger | a strike on the building | a nearby strike, switching events |
| Relevant for PV | if present on the building | sensible in many cases |
Simplified overview, as of: July 2026. The specific assessment is made by the electrical specialist company at the building.
The interplay matters: where external lightning protection exists, the solar system has to be cleanly integrated into that concept so it doesn't undermine it. Where none exists, internal surge protection remains the means against the far more common indirect surges.
Is surge protection mandatory or just recommended?
That can't be answered in one sentence for everyone – it depends on the building. The applicable installation regulations and the assessment of the electrical specialist company connecting the system, who is liable for it, are decisive.
As a rule of thumb from practice: for a new solar system, surge protection is in many constellations the sensible and often required solution, because it costs little relative to the system's value and protects the inverter. Decisive factors include whether external lightning protection is present, the length and routing of the cables, and the building's exposure.
What you as the owner should get out of this: a traceable statement in the quote on whether and what surge protection is planned – and why. If the point is missing entirely, or listed only as an expensive extra with no justification, it's worth asking. A reputable specialist company explains the decision; it neither claims every system needs the maximum, nor quietly leaves the topic out.
Surge protection is one of the items customers rarely have on their radar when comparing quotes – and one that can make the difference between two offers. We see both: systems with no protection at all, where the inverter had to be replaced after a thunderstorm, and quotes that flatly include the most expensive package even though the building doesn't call for it. Our approach goes via an on-site assessment – is there external lightning protection, how are the cables routed, how exposed is the house. That determines what's needed. As much as makes sense, not as much as possible.
Frequently asked questions
Isn't building insurance enough instead of installing surge protection?
Those are two different things. Insurance at best reimburses the damage after the fact, surge protection prevents it in the first place wherever possible. A defective inverter always also means lost yield until a replacement arrives. Prevention and insurance aren't mutually exclusive, they complement each other.
Does surge protection also help against a direct lightning strike on the house?
Only to a limited extent. External lightning protection is responsible for a direct hit. Internal surge protection works against the far more common indirect surges that reach the house via the wiring. Where a building has external lightning protection, both systems need to be coordinated with each other.
Can I retrofit surge protection?
In many cases, yes. The arresters sit in the electrical installation and can often be added. Whether that's sensible and feasible at reasonable effort on your existing system is assessed by the electrical specialist company based on the existing installation.
How long do surge arresters last?
They can "trip" during a strong event and wear out in the process. Many devices show their state via an indicator. Checking them is therefore sensibly part of the system's ongoing operation – a tripped arrester no longer protects and gets replaced.
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With every quote, we assess the surge and lightning protection needed for the specific building – with a traceable justification, no blanket packages.
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Sources: General electrical engineering basics on surge and lightning protection for photovoltaics; installation practice and empirical data from ecoEn GmbH, Zurich region. The applicable installation regulations and the assessment of the electrical specialist company are decisive.
Last updated: 9 July 2026 · Author: ecoEn editorial team
