Solar modules are tested for hail and are generally robust enough for Swiss conditions – their front glasses withstand normal to heavy hail. The decisive factor is the hail resistance class of the module, which indicates which grain size it survives undamaged. A residual risk with extreme hail remains, which is why the system belongs in the building insurance. (As of: July 2026)
Key points in brief
- Solar modules are tested for hail; the robustness is indicated in hail resistance classes.
- For most locations in the region, standard modules are sufficient – their glasses are designed for heavy hail.
- In particularly hail-prone locations, a conscious look at a higher resistance class is worthwhile.
- There is never a total risk: extreme hail can cause damage – that is what the insurance is for.
- After a severe hailstorm, a professional check is worthwhile, even if everything looks intact from below.
This guide explains how robust modules are against hail and what matters in the selection. If damage has already occurred to your system after a storm, Hail damage to the solar system: How to proceed guides you step by step through documentation, reporting to the insurance and professional checking.
How hail-proof are solar modules?
The concern is understandable – glass on the roof, and in summer the thunderstorms roll through. The all-clear right away: the front glass of a solar module is not window glass, but toughened special glass, built to withstand decades of wind, weather and precisely also hail. For this, modules go through standardised tests in which ice balls of a defined size are shot onto the surface at a defined speed. What passes this test withstands significantly more in the field than what an average summer thunderstorm brings.
This explains why hail damage to solar systems – measured against the number of systems and the frequency of hail – is rare. The modules are among the more robust components on the roof; often surrounding roof tiles or the car in the driveway take damage rather than the system.
What do hail resistance classes mean?
To make robustness comparable, there are hail resistance classes: they classify a module according to which grain size it survives undamaged – the higher the class, the larger the hailstone the module can withstand. In Switzerland, the hail register of the Association of Cantonal Fire Insurances (VKF) lists tested components in the classes HW 1 to HW 5 – the number corresponds to the grain diameter in centimetres that the component survives in the standardised test. Standard solar modules typically achieve HW 3 (3 cm grain), more robust products HW 4 or HW 5. For you as a building owner, this is the one key figure that counts when it comes to hail: it allows a comparison between modules without having to know the test standards in detail.
Since October 2025, modules that have been tested by an internationally accredited test body according to the standard IEC 61215 can also be entered in the hail register. The assignment is fixed:
| Tested grain size | Hail resistance class | corresponds to |
|---|---|---|
| 45 mm | HW 3 | 3 cm grain diameter |
| 55 mm | HW 4 | 4 cm |
| 65 mm | HW 5 | 5 cm |
Assignment according to hagelregister.ch, new regulation for PV modules since October 2025.
A detail that repeatedly causes confusion in data sheet comparisons: a module tested according to IEC 61215 receives a lower class than an equivalent module from the VKF test – the VKF test regulations are stricter, including significantly colder ice and on-site checks. Anyone who puts two data sheets side by side should therefore not only look at the class, but also at the procedure according to which it was tested.
The practical classification: for most locations, standard modules with a standard class are sufficient. Anyone building in a known hail-prone location deliberately chooses a higher resistance class – a conscious step that leaves the system better off in the extreme case. This information belongs to the technical points that a serious quote specifies concretely; where it is missing, it is worth asking.
What does the risk at my location depend on?
Hail is distributed very unevenly regionally – Switzerland knows pronounced hail zones, and the risk of a location can be estimated. Three factors play together:
| Factor | Influence |
|---|---|
| Regional hail frequency | Core zones (e.g. Pre-Alps, Jura southern foot) carry a higher risk |
| Hail resistance class of the module | higher class = more reserve with large grains |
| Roof inclination | modules hit flat take the force more directly than steep ones |
Simplified overview, as of: July 2026. The specific risk of a location can be classified via the national hail hazard maps from MeteoSwiss (project "Hail climate Switzerland", accessible via map.geo.admin.ch).
The planning logic results from this combination: in an average location in the region, hail is no reason for concern – standard modules are sufficient. In a designated hail zone, a conscious reach for a higher resistance class is a cheap insurance that one takes once when buying and forgets afterwards.
Why HW 3 is not sufficient everywhere – and what we make of it
The data basis has shifted. A new hail map has emerged from the project "Hail climate Switzerland" (MeteoSwiss, FOEN, building insurances, SIA), which resolves finer than the previous one. Swissolar draws a clear conclusion from this: many new areas with grain diameters over 4 cm (50-year return period) are designated – and in these areas the class HW 3 will no longer be sufficient. In other locations, the question of whether HW 3 or HW 4 is right only arises in the first place. The standard SIA 261/1 (2020) with the hail map in Appendix G1 is currently still decisive for structural design; the new map is gradually flowing into the regulations.
For planning, this means: the resistance class is not a catalogue decision, but a location decision. A roof in the Swiss Plateau and a roof in a pre-alpine location do not have the same requirement – and between a city location and an exposed slope, just a few kilometres can make the difference.
How we handle it: We determine the resistance class on a project basis – according to the hail hazard at the specific address, the roof inclination and the exposure of the building. We do not have a blanket class for all projects; where the hazard situation suggests it, we go one level higher. We also ensure that the modules installed are entered in the hail register; the next section explains why this is crucial for the insurance.
Sources: Swissolar, leaflet "Hail damage to solar systems"; hagelregister.ch; SIA 261/1 (2020). As of: September 2026.
What applies in the event of a claim?
No module is indestructible, and extreme hail – fist-sized grains, such as individual storms bring – can cause damage. The storm on 28 August 2026 in the north of the Canton of Zurich with 4 to 6 centimetre grains showed this: the Building Insurance Canton of Zurich expects around 200 million francs in building damage, photovoltaic systems are among the common damage patterns (GVZ, as of September 2026). This is exactly why there are two safety nets.
The first is the insurance. Hail counts as elemental damage, and solar systems belong in the building insurance – therefore, always register a new system and clarify the cover instead of finding out in the event of a claim. The maintenance guide covers how this fits into the overall picture of operation and protection.
The second is the professional check after the event. After a severe hailstorm, the system should be checked, even if everything looks intact from below: fine cracks in the glass – so-called micro-cracks – are often not visible to the naked eye, but show up later in the yield or in the electroluminescence test. A documented finding shortly after the event also secures claims against the insurance. How exactly you proceed – from the first photos to reporting – is in Hail damage to the solar system: How to proceed. This check is one of the clear occasions when a professional belongs on the roof – in contrast to the routine annual check that you do from the ground.
Important for differentiation: hail damage is something different than the normal, age-related loss of performance. If a system slowly declines over years, that is degradation and not damage – a sudden slump after a storm, on the other hand, is a case for checking and insurance.
If after the hail not the system but the roof is damaged – and there is no system on it yet at all –, the order decides the costs: anyone planning solar anyway schedules the installation during the repair appointment as long as the scaffolding is up. What the insurance pays for this and what not is explained in the guide Roof renovation and photovoltaics.
After every major hail summer, our phone rings – and the most common message is the reassuring one: "We checked, the modules look intact." Mostly that is true too. Nevertheless, we advise a check after a severe storm, and for a reason that you can't see from the street: hairline cracks in the glass or in the cells do not show up immediately, but gradually in the yield over the following months. Anyone who has a specialist company look at it directly after the event has won two things – clarity about the condition and, if there is something after all, a documented finding for the insurance, as long as the connection with the storm is undisputed. What we have never experienced, however, is the system being destroyed by a normal summer thunderstorm. The modules can withstand more than most trust them to.
Frequently asked questions
Can normal summer thunderstorms damage solar modules?
Generally not. The toughened front glasses are designed for heavy hail and easily withstand what an average thunderstorm brings. Damage only occurs with exceptionally large hailstones, such as only individual extreme storms bring.
How do I recognise how hail-proof a module is?
By the hail resistance class – it indicates which grain size the module survives undamaged; the VKF hail register knows the classes HW 1 to HW 5, standard modules are at HW 3. This information should be in the quote or in the data sheet. In hail-prone locations, a deliberate reach for a higher class is worthwhile; in average locations, the usual one is sufficient.
Does the insurance cover hail damage to the solar system?
Hail counts as elemental damage and is generally covered by the building insurance – provided the system is registered. Therefore, always register a new system and actively clarify the cover. The details depend on the canton and policy.
Do I have to have the system checked after a hail?
After a severe hailstorm, yes, even if everything looks intact from below. Micro-cracks in the glass or in the cells are hardly visible to the naked eye, but reduce the yield. A professional check provides clarity and, if necessary, supplies a documented finding for the insurance.
Are elevated modules on the flat roof more at risk of hail?
Not fundamentally – the impact angle of the hail is decisive. Steeper inclined modules take the force less directly than flat-lying ones. In practice, this plays a subordinate role compared to the resistance class and the regional hail frequency.
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Plan safely – also for the weather.
We select the modules suitable for your location and show the hail resistance class in the quote – and are there for the check after a storm.
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Sources: VKF hail register (hagelregister.ch, classes HW 1–5); MeteoSwiss, national hail hazard maps "Hail climate Switzerland" (map.geo.admin.ch); Swissolar; manufacturer data sheets (hail resistance classes); empirical values from the installation and service practice of ecoEn GmbH, Zurich region. As of: July 2026.
Last updated: 9 July 2026 · Author: ecoEn editorial team
