Solar panels have become an increasingly popular solution for producing green energy. Reliable and durable, they transform sunlight into electricity for homes, businesses and industrial infrastructure. However, even the best performing solar panels can be affected by a dangerous and often ignored phenomenon: the hot-spot effect (or hot spot).
This phenomenon occurs when certain cells of the panel overheat locally, leading to loss of efficiency, degradation of materials and, in extreme cases, risk of fire.
To understand why this happens, we need to analyze how a photovoltaic module works and what causes these hot spots to appear.
⚙️ How solar panels work
A photovoltaic module is made up of tens of solar cells interconnected in series. In such a configuration, the total current is determined by the weakest cell.
If all the cells produce the same amount of energy, the electrical flow is uniform. But if one of them generates less current—due to shade, dirt, or a microcrack—the balance breaks.
That cell becomes a local electrical resistance, which absorbs energy instead of producing it. The dissipated energy turns into heat, forming a hot spot, an area where the temperature can rise by more than 100°C compared to the rest of the solar panel.
🔬 The causes of the hot-spot phenomenon
The hot-spot phenomenon is caused by mechanical, electrical or environmental factors. Here are the most common situations encountered in photovoltaic systems:
1️⃣ Partial shading
Even a leaf, a speck of dust or an antenna can block some of the light. The affected cell no longer generates power, but remains connected to the current string, being forced to operate in reverse bias. The result is the accumulation of heat and the appearance of the hot spot.
2️⃣ Microcracks or cell damage
During mounting or handling, cells may develop invisible microcracks. They create uneven resistance, generating local areas of overheating.
3️⃣ Manufacturing defects
Imperfect solders, uneven layer of semiconductor material, or doping variations can lead to differences in performance between cells.
4️⃣ Accumulated dirt
Deposits of dust, pollen, soot or bird droppings reduce local irradiation and increase the risk of the hot-spot phenomenon.
5️⃣ Defective bypass diode
Each group of cells is protected by a bypass diode, which allows current to bypass shaded or defective areas. If the diode fails, energy continues to flow through the affected cells, causing overheating.
6️⃣ Aging of materials
UV radiation, humidity and temperature variations affect the EVA layer and the structure of the panel. Over time, they lose their grip and can promote the appearance of hot spots.
🌡️ How a hot spot manifests itself
The hot-spot phenomenon is not visible to the naked eye. It can only be detected by a IR thermographic inspection (in
frarosu), which shows the temperature differences between the panel cells.
Typical signs of a hot spot include:
high temperature areas (visible only in thermal imaging);
local discoloration of the EVA layer (brown, yellow or gray); [#$$#]
power drop at the module level;
burn marks or cracks around the connections.
📉 Effects on performance and lifespan
A single hot-spotted solar panel can reduce the efficiency of the entire array by up to 20%.
In the long term, the effect leads to:
permanent degradation of materials;
increasing internal resistance;
shortening the lifetime of the module;
risk of fire in electrical contact areas.
According to the study Power loss and hotspot analysis for photovoltaic modules affected by PID, modules affected by degradation can develop hot-spots that raise local temperatures and lead to average power losses of ~25 %.
🧰 How to prevent the hot-spot phenomenon
✅ 1. Functional bypass diode
Periodic checking of the bypass diodes ensures protection of the cells against reverse bias.
✅ 2. Professional cleaning
Maintenance and cleaning of solar panels 2–3 times a year removes deposits that can cause local shadows.
✅ 3. Annual thermographic inspections
IR camera scans quickly detect incipient hot spots. Ecosolaris offers such specialized services for residential and industrial systems.
✅ 4. Professional installation
Correct installation of solar panels prevents mechanical cracks and ensures optimal electrical contact.
✅ 5. Intelligent monitoring
Modern monitoring platforms enable rapid identification of local power outages.
🛠️ EcoSolaris – maintenance that maintains efficiency
La EcoSolaris, we carry out complete checks for photovoltaic systems:
thermographic inspections with professional equipment;
testing connections and bypass diodes;
environmental cleaning and performance analysis;
technical reports with precise recommendations.
Thus, the solar panels maintain their optimal performance and long-term safety.
For details about our services, you can consult the dedicated page:
➡️ Maintenance of photovoltaic systems
🔒 Conclusion
The phenomenon hot spot is one of the main causes of solar panel degradation.
Although apparently minor, its local effect can affect the efficiency of the entire system and the safety of the plant.
With proper installation, regular inspections and professional maintenance, the risks can be completely avoided.
Prevention is, in green energy, the best form of protection.
