Hotspots on solar panels: what they are and why your inverter misses them
A hotspot is a spot on a solar panel that gets hotter than the rest. Sounds harmless, but a hotspot is almost always a symptom — of a faulty cell, a bad connection or soiling — and it quietly eats into your yield.
Why does this matter?
Where a cell or cell section no longer works properly, the energy is turned not into current but into heat. That warm spot is the hotspot. It costs yield immediately, and a strongly heated cell can damage the panel further over time. The causes vary: cell cracks from microcracks or hail, an activated bypass diode, potential-induced degradation (PID), soiling or shade, and poor solder or plug connections. Each cause leaves its own pattern.
Why your inverter misses them
The inverter measures yield per string or for the whole installation — not per panel, let alone per cell. A weak cell, or even a whole weak panel, disappears into the average until the loss is large enough to notice. In practice we saw an array of some thirty inverters, two of which produced nothing at all — those stood out. But the thermographic scan additionally revealed dozens of hidden hotspots at module level that the inverter app had never flagged, and which together were quietly removing yield.
How does this work in practice?
We fly the installation with a Matrice 30T and measure radiometrically. Every hotspot gets a temperature and a GPS position, and the pattern reveals the likely cause: a single warm cell points to a crack, a warm substring to a diode, a checkerboard pattern to extensive damage. The report and all images are delivered through a dedicated client portal — DronePortal: one link, with the report and thermal and visual images in one place.
Common mistakes
- Relying on the inverter alone. It hides damage at cell and module level.
- Checking only visually. Most hotspots are invisible to the eye.
- Measuring at the wrong time. Without enough irradiance the defects don't heat up enough.
Why with a drone (and why Droneview)?
A drone captures every module individually, which neither the inverter nor a visual walk can do. Droneview measures EASA-certified and radiometrically with the Matrice 30T, reads the hotspot patterns and delivers a structured, localised report — so you know which panel needs action and why.
Frequently asked questions
What causes a hotspot on a solar panel?
A hotspot appears where a cell or cell section no longer works properly and turns energy into heat instead of current. Causes include a cell crack (microcracks, hail), an activated bypass diode, PID, soiling or shade, and poor connections.
Why does my inverter miss one faulty string?
An inverter measures yield per string or for the whole installation, not per panel or cell. A single weak cell, or even a whole weak panel, disappears into the average until the loss is large enough.
Is a hotspot dangerous?
A hotspot costs yield first of all, but a strongly locally heated cell can damage the panel further over time and poses a risk in extreme cases. Early detection prevents worse.
How often should I check for hotspots?
For larger or critical installations a periodic thermographic check is worthwhile, and certainly after hail or other damage. That way you see the evolution and can act or claim in time.
Want to know what your inverter doesn't show?
A thermographic scan captures every module — with a report per hotspot.
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