Can Hail Destroy Solar Panels? What the Lab Tests Actually Prove

If you live anywhere hail falls in golf-ball-sized chunks, the question isn't really whether solar panels look fragile — it's whether they can survive the storm season. The answer comes from two places: a real hailstorm that pounded a national research lab, and the laboratory test that every certified panel must pass before it reaches your roof.

The storm that tested a national lab

On May 8, 2017, a severe hailstorm ripped through the Denver area, shattering car windows and denting roofs across the metro [1]. Sitting directly in its path was the National Renewable Energy Laboratory (NREL), whose campus hosts more than 2.5 megawatts of solar — over 3,000 panels in all. When technicians inspected the array after the storm, they found exactly one broken panel [1].

That lone cracked panel tells an important story of its own: it wasn't hit once. It was struck by dozens of hailstones landing in almost exactly the same spot, which built up a micro-crack network until the panel failed. One hit in one place wasn't enough — it took repeated strikes to the same spot [1].

How panels are certified for hail

Panels don't earn that kind of durability by accident. Before a module can be sold as certified, it must survive a standardized hail test: ice balls roughly the size of ping-pong balls are fired at the panel in multiple locations at about 70 miles per hour [1]. The international standard behind this test, IEC 61215-2:2016, specifies hailstones of 25–55 mm in diameter, weighing 7.5–80 grams, fired at 23–34 meters per second [2].

NREL is part of the International Photovoltaic Quality Assurance Task Force, the body that develops these standardized tests — covering hail, thermal cycling, humidity, UV exposure, and high-voltage stress — so the certification is consistent across manufacturers and countries [1]. That standardization matters for homeowners: a panel certified to the international standard has passed the same hail hurdle [2] whether it was made in Asia, Europe, or the United States, so the label is a meaningful durability baseline rather than marketing language.

Note what the test does not assume: a single hit. The ice balls strike the module in multiple places at about 70 miles per hour, so passing means the panel survived impacts across its whole surface, not just one lucky spot [1]. That is precisely why the NREL case is so telling — real hail behaved like the test, and it took dozens of concentrated strikes to defeat a single panel.

Why glass thickness matters

Passing certification is the floor, not the ceiling. A study published in Renewable Energy pushed panels further by firing a 45 mm ice ball at modules with different glass thicknesses, and the results were stark: 21.8% power loss in panels with 2.8 mm glass, 11.74% loss with the standard 3.2 mm glass — but only 0.81% loss with 4 mm glass, which also withstood a larger 55 mm ball [2].

The study's authors concluded that the current 3.2 mm commercial standard is not suitable for hail-prone regions and recommended 4 mm glass instead [2]. In plain English: the thickness of the glass over your panels is the single biggest variable in hail survival, and the industry's default is calibrated for ordinary weather, not hail country.

The gap between those numbers also shows why a panel can be certified yet still fail in a real storm. The 3.2 mm standard glass lost 11.74% of its power after a 45 mm impact, while the 4 mm glass lost just 0.81% and went on to survive an even larger 55 mm ball [2]. Certification proves the panel survives the standard test; glass thickness decides how much headroom it has when the storm exceeds it.

When hail damage does happen

This isn't to say hail never harms solar. In May 2019, a hailstorm at a 178-megawatt plant in Texas caused $70 million in damage to more than 400,000 modules [2]. Utility-scale arrays in hail corridors are the clearest proof that extreme storms can overwhelm standard panels — which is exactly why the glass-thickness research focuses on those regions.

For a homeowner, the lesson scales down directly: a residential array is a smaller target with the same glass. If the 3.2 mm standard can be overwhelmed on a 400,000-module plant in a hail corridor, a roof in the same corridor deserves the stronger glass the researchers recommend [2].

What this means for your roof

For most homeowners, the takeaway is reassuring: certified panels are already hail-tested at speeds and sizes that would worry any homeowner. But if your address sits in a hail belt, the one specification worth asking your installer about is glass thickness. Panels with 4 mm glass survived a 55 mm ice ball in lab testing with near-zero power loss, while the standard 3.2 mm panels did not [2]. And remember what the NREL campus showed: it took dozens of strikes to nearly the same spot to crack even one panel [1]. Hail damage is real, but catastrophic failure of a certified panel from a single storm takes far more than most storms deliver.

Ask the question before you sign, not after the storm: which panel model are you quoting, and what glass thickness does it use? Get the answer in writing before you decide.

Sources

• [1] U.S. Department of Energy (CMEI) — Hail No! National Lab's Solar Panels Survive Severe Storm — https://www.energy.gov/cmei/articles/hail-no-national-labs-solar-panels-survive-severe-storm
• [2] The American Ceramic Society — Protecting solar panels from hail: the thicker the glass, the better — https://ceramics.org/ceramic-tech-today/protecting-solar-panels-from-hail-the-thicker-the-glass-the-better/

Verified: 2026-10-14

Disclosure: This article was drafted with AI assistance and reviewed by a human editor. Figures reflect sources available on the verified date; confirm current program rules before acting.