Hotspots on solar panels: silent wreckers of your returns
Hotspots can cost up to 1% in losses per panel per year and pose a fire hazard. Find out about the causes, detection and prevention with an IR scan.
By Hendrik Vandervoort3 min read
A solar panel is supposed to convert sunlight into electricity, not heat. Nevertheless, localised spots can occur where cells overheat: so-called hotspots. They are often invisible to the naked eye, but reduce efficiency and shorten the life of your installation. In this article, we explain what hotspots are, how to recognise them, how to prevent hotspotting and how to Solarco supports you in this.
1. What is a hotspot on a solar panel?
A hot spot is a local area on a solar cell that heats up higher than the surrounding cells, usually > 20 °C temperature difference. The cell starts acting as a resistor instead of a generator, converting energy into heat. This can lead to:
- Deformed cells or discolouration.
- Glass damage due to thermal stress.
- Faster degradation of EVA film and backsheet.
- Fire risk at extreme temperatures (> 250 °C).
"Hotspots often arise stealthily. By the time you see something visually, permanent efficiency has already been lost," warns Hendrik, CEO of Solarco.
2. The main causes of hotspot formation
2.1 Shadow and pollution
- Leaves, bird droppings or loose branches block light → cell underloaded → current from surrounding cells runs through the shaded cell → heating up.
- Dust and dirt film increase local resistance.
2.2 Production defects and degradation
- Welding error or microcrack during production.
- Potential Induced Degradation (PID) can increase cell resistance.
2.3 Poor assembly or design
- Connector corrosion or loose terminals increase transition resistance.
- Series string with unequal orientations or different panel types.
2.4 Bypass diode defective
A broken bypass diode no longer switches a shaded cell out of the series, so full current has to pass through it → hot spot.
3. Impact on efficiency and safety
| Temperature hotspot | Possible damage | Efficiency loss |
|---|---|---|
| 80-100 °C | Calcification encapsulant | 2-3 % local |
| 100-150 °C | Solder melting, cell breakage | 4-6 % local |
| > 200 °C | Glass tip melts, fire risk | 10 % or more + security risk |
Even hot spots of 85 °C can lead to 1 % annual yield loss per affected panel. This seems little, but at system level, it can cost hundreds of euros per year.
4. How to recognise hotspots?
- Infrared thermography: with an IR camera you detect temperature differences of 2 °C.
- Electroluminescence (EL) photo: making microcracks visible.
- Performance monitoring: unexplained drop in string yield.
- Visual inspection: discolouration, brown spots or slight cracks in glass.
"One annual IR scan in cloudy weather reveals 90 % of hotspots," says Sander, chief operator at Solarco.
5. Preventing hotspots: best practices
5.1 Regular cleaning
- Remove dust, pollen and bird droppings at least once a year.
- Use pure water and soft brushes
- Read more about our solar panel cleaning service.
5.2 Professional inspection
- Annual IR scan.
- Check connectors, string voltages, insulation resistance.
- Read more about our inspections.
5.3 Smart system design
- Ensure identical panels in one string.
- Avoid partial shading by trees/roof dormers.
- Install power optimisers or micro-inverters on high-risk roofs.
5.4 Rapid replacement of defective components
- Bypass diode broken? Panel repair or replacement.
- Microcrack? Consider glass-film repair or panel change.
- Here, too, we can help you with our professional solar panel maintenance
6. How Solarco helps prevent & fix hotspots
6.1 IR thermography package
- Drone scan For large solar parks up to 25 ha.
- Handheld Flir scans for residential and SME roofs.
- Report showing hotspot locations, temperature difference and priority score.
6.2 Cleaning & maintenance service
- Pure water cleaning makes cells dirt-free, minimises shadowing.
- Robotic cleaning for flat roofs up to 600 m²/hour.
6.3 Repair & replacement advice
- Analysis of bypass diodes, string anomalies.
- Delivery & installation replacement panel within 48 h in Belgium.
- Help with warranty claims with photo documentation.
6.4 Preventive maintenance contract
- Annual cleaning + IR scan + reporting.
- Alarm service: remote monitoring of string data → notification at > 5 % deviation.
10. Conclusion & call-to-action
Hotspots are silent wreckers that not only destroy your return undermine, but also create fire hazards. Regular cleaning, professional IR scanning and prompt repair prevent costly surprises.
Get Solarco to do a hotspot scan today and receive a comprehensive report with recommendations within 24 hours. Schedule your appointment directly via our service page and guarantee a long, safe life of your PV plant.
Share this article with fellow solar panel owners to master hotspots together!
Frequently asked questions
What is a hotspot on a solar panel?
A hotspot is an area of a panel that overheats badly because a cell is no longer passing current, for example due to dirt, shading, a micro-crack or a cell defect. That cell then consumes energy instead of generating it, which reduces yield and, over time, creates a risk of fire or damage. A thermographic (drone) inspection detects hotspots early.
What is a thermographic inspection of solar panels?
In a thermographic inspection, infrared cameras capture temperature differences that point to defects invisible to the naked eye, such as hotspots, faulty cells and string interruptions. The inspection is non-destructive and is carried out without dismantling the installation. On large solar parks, drones are used to scan extensive areas quickly.
How does a solar panel drone inspection work?
A drone inspection combines high-resolution photography with thermal imaging and georeferencing to pinpoint and quantify defects precisely. This reveals hotspots, cold cells, faulty bypass diodes and string problems that an ordinary visual check would miss. The approach is particularly useful for large roofs, solar parks and hard-to-reach sites.
Why are bird droppings so bad for solar panels?
Bird droppings are acidic and cause permanent damage over time, and they also cast hard, concentrated shade over a single cell. This can cause a local yield loss of around 20% and trigger the bypass diodes, leading to hotspots and faster degradation. The damage is far greater than such a small mark would suggest, so remove bird droppings promptly.
Why isn't a visual inspection of solar panels enough?
A visual inspection only reveals surface problems such as heavy soiling, broken glass, loose cabling or discolouration. Much of the yield loss and many safety risks, however, originate beneath the glass or in the connectors (micro-cracks, developing hotspots and PID degradation), and these can only be detected with thermography or electrical measurements. A combined approach gives you the full picture.
How often do solar panels need to be inspected?
A visual and electrical check every two years is sufficient in many cases, while an annual inspection is advisable in environments with a lot of dust, salt or heavy industry. For larger installations and parks, a thermographic inspection every one to two years is recommended. An additional check is sensible after severe weather or if output drops for no apparent reason.
