Understanding your hotspot loss
Why a hotspot is different from ordinary shading
A hotspot forms when a shaded, cracked, or defective cell gets forced into reverse bias by the healthy cells around it in the same circuit, causing that cell to dissipate power as heat rather than produce it. Unlike ordinary shading, which simply blocks light, a hotspot actively consumes power that the rest of the system generated, making it a more serious issue per affected cell. A NLR field study on shaded PV modules notes that bypass diodes exist specifically to prevent the reverse-bias heating that leads to hotspots in shaded cells.
How hotspots get detected
Infrared, or IR, thermal imaging is the standard detection method, since a hotspot cell runs noticeably hotter than the surrounding cells around it. A drone-mounted or handheld IR camera can spot temperature differences that aren't visible to the naked eye, which is why routine thermal inspections are valuable even when a system seems to be performing normally. DOE's own solar operations and maintenance resources list this kind of routine inspection as one of the standard practices for catching micro-cracking, hotspots, and other developing issues before they become bigger problems. Check the partial shading tool too, since persistent shading is one of the most common hotspot triggers.
The safety dimension beyond output loss
Yes, in more severe cases. A hotspot running significantly hotter than the surrounding panel can, over time, damage the panel's backsheet or encapsulant material, and severe cases have been linked to fire risk in rare circumstances. Any hotspot showing a large temperature excess should be evaluated by a professional promptly, regardless of how small the calculated output loss appears.
What typically triggers a hotspot
Common triggers include persistent partial shading on one cell, a manufacturing defect, a microcrack that disrupts current flow, or debris like bird droppings sitting on a single cell for an extended period, all of which can force that cell into the reverse-bias condition that generates heat. Addressing the root cause, not just the symptom, is the long-term fix. Check the string mismatch loss calculator for how an affected panel interacts with the rest of its circuit, and the microinverter vs string inverter output tool for how equipment choice affects whether that one panel's problem spreads to its neighbors.
What to do with this number next
If a microcrack may be the underlying cause, check the microcracks estimator too, and consider a professional inspection promptly given the safety dimension involved here beyond pure output loss. If that loss is a warranty question, the warranty coverage value calculator prices the coverage.