Recognising hail damage on solar panels: what the naked eye misses
After a severe hailstorm, a solar array often looks untouched. No broken glass, no visible dents — so everything's fine? In practice we see the opposite: the most dangerous hail damage is exactly the damage you don't see.
Why does this matter?
Hail rarely hits a panel hard enough to break the glass. Far more often it leaves hairline cracks in the silicon cells beneath the glass — microcracks. The panel still looks pristine and keeps producing for the first few weeks. But those cracks grow under thermal expansion, vibration and moisture ingress. Cells or cell sections become electrically isolated, start acting as a resistor and heat up. Months to years later the yield drops — often just outside the warranty or claim window.
Anyone relying on a visual check therefore wrongly declares a damaged array "fine". The result: a rejected or weakened insurance file, and creeping production loss that only shows up once it is already substantial.
How does this work in practice?
A reliable check after hail does not rely on the eye, but on temperature. A faulty or interrupted cell no longer carries current and, under load, heats up measurably more than its neighbours. With a radiometric thermal camera that difference shows up as a hotspot.
We fly these inspections with a Matrice 30T: a stabilised flight at a fixed height across the entire array, capturing every module under equal irradiance. The radiometric data records the temperature per pixel, so a hotspot is not only visible but also measurable. That lets us tell a real cell crack from a reflection or some dirt, and tie every finding to the right module by GPS.
Common mistakes
- Only a visual walk-around. Microcracks and isolated cells are invisible to the eye. "No broken glass" does not mean "no damage".
- Trusting the inverter app. It measures per string, not per panel. One weak cell averages away in the total.
- Measuring at the wrong time. With too little irradiance the temperature difference (delta-T) is too small and faulty cells go unnoticed.
- An ordinary thermal photo instead of radiometry. Without per-pixel temperature values you cannot quantify or substantiate a hotspot.
- No emissivity or reference correction. Glass reflects; without correct settings you measure the sky instead of the panel.
Why with a drone?
A drone scans an entire array in a fraction of the time of a manual check, without anyone having to climb onto the installation. Every module is viewed at the same angle and lighting, which makes the images comparable. Each hotspot gets a GPS position, so the repairer knows exactly which panel to replace. And because the flight is repeatable, you can redo the exact same measurement a year later to show the change.
Why Droneview?
Droneview is an EASA-certified drone operator specialised in radiometric thermography with the Matrice 30T. We have carried out hundreds of PV inspections, from rooftop installations to multi-megawatt solar farms, and deliver an independent report that holds up with both insurer and installer. No colour pictures, but measurable data and a clear diagnosis.
Frequently asked questions
Can hail damage to solar panels be invisible?
Yes. Hail rarely breaks the glass but often causes hairline cracks in the cells beneath it (microcracks). The panel looks intact and keeps producing at first, while the yield only drops months later.
Is the inverter app enough to detect hail damage?
No. An inverter measures yield per string, not per panel or cell. One or a few weak cells disappear into the average and stay invisible until the loss is large.
When should I inspect after a hailstorm?
As soon as possible for the insurance file, but the thermographic measurement itself needs enough solar irradiance (ideally above 600 W/m²) so faulty cells heat up enough to show as hotspots.
Does an ordinary thermal camera see this too?
Only a radiometric camera provides a real temperature reading per pixel, which you need to quantify and substantiate a hotspot. A cheap colour thermal photo shows patterns, not measurable values.
Suspect hail damage on your installation?
Have your array checked with thermography and get an independent report that holds up with your insurer.
Request a quote