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Frequent defects & damage to solar modules & solar systems

Solar modules: Recognising defects and counteracting them at an early stage

Solar modules generally have a service life of at least 20 years and can usually be operated for longer. However, internal and technical factors as well as external influences can lead to defects that have a negative impact performance and service life of your photovoltaic system.For example, hotspots, slug marks and PID effects can occur on the module side. We have for you typical defects in solar modules compiled - by damage to your solar panels you can take countermeasures at an early stage to ensure the efficiency of your system in the long term.

Ursachen für Defekte an Solarmodulen

What causes defects in solar panels?

In general, solar modules are subject to a natural ageing process. Over time, the performance of the solar cells can deteriorate, leading to a drop in output. This is normal wear and tear, which you must take into account when operating your solar system.

Fundamentally important in order to avoid defects in solar modules, are a proper installation and regular maintenance. Improper installation, for example, where the solar modules are not properly anchored or aligned, can lead to physical damage and impair performance. Furthermore Defects in solar modules are due to a variety of causes .

Other causes of damage to solar modules

  • Umwelteinflüsse: Extreme Wetterbedingungen wie Hagel, Sturm, Schnee, extreme Temperaturen (Kälte und Hitze) können zu physischen Schäden an den Solarmodulen führen. Risse, Brüche oder Abplatzungen können auftreten.
  • Overvoltages: Lightning strikes or voltage fluctuations in the power grid can cause electrical surges that damage the solar modules.
  • Contamination: Deposits of dirt, dust, pollen, bird droppings and other impurities on the surface of the solar modules can impair performance. Neglecting the cleaning can lead to significant performance losses in case of doubt.
  • Humidity: Moisture that penetrates the solar modules can lead to corrosion of the electrical contacts and impair the functionality of the modules.
  • Electrical problems: Defects in the electrical components of the solar modules, such as bypass diodes or connection cables, can impair the performance of the modules.
  • Animals: Birds, rodents or other animals can cause damage to solar modules by scratching the surface, damaging cables or building nests.
If solar modules are damaged, they should be repaired as quickly as possible to prevent further damage to the PV system.

Flash it - only then can damage be recognised.

The modules are visually flawless - do they deliver what they promise? Get a quote for your flash test.

From our practice: Example flash test

Our customer commissioned us to test modules that looked completely flawless after storm damage. Our flash test revealed massive damage to the structure of the module as well as a drop in performance of up to 17%.

Strom-Spannungs-Kennlinie bei Flash Test
Vergrößerung Zellschaden
Vergrößerung Zellschaden
Zellschaden Flash Test Solarmodul
Vergrößerung Zellschaden
Flash Test defektes Solarmodul

Detect defects with flash tests

Flash tests check the performance of your solar modules. They provide indications of defective panels. Get a quote for your flash test.

Frequent defects, damage and problems with solar modules


So-called hotspots for solar modules are areas where the temperature rises due to uneven energy absorption or other factors (cracks, poor connections, interruptions in the cabling). Hotspots can lead to serious problems, including damage to the solar cells and in extreme cases even melting or fires. Causes of hotspots can include shading, defective cells, faulty cabling, excess voltage and insufficient heat dissipation.

  • Hotspots can be recognised by brown burn marks.

Cracks/breaks in the front glass

The front glass of a solar panel serves to protect the underlying solar cells from external influences. At the same time, it must ensure that as much light as possible reaches the solar cells. Cracks or fractures in the glass can be caused by installation errors, mechanical stress, temperature fluctuations or hail. Glass breakage can impair the light transmission and the protective effect of the glass. If water penetrates the module, this leads to corrosion of the electrical contacts and possibly to short circuits. Overall, the solar module suffers a loss of performance.

  • Subject your modules to regular visual inspections - and inspect your PV system especially after extreme weather events in order to quickly recognise breaks in the front glass.


In contrast to comparatively easily recognisable fractures in the front glass, the microcracks in the glass or in solar cells cannot be detected directly. Instead, they often only become visible through the penetration of moisture and dirt. Microcracks can lead to degradation over time, which is reflected in a loss of module performance. Reasons for the formation of microcracks include mechanical stresses (such as hail, stone chipping, impacts), thermal stresses caused by extreme temperature fluctuations, manufacturing defects and material fatigue. 

  • Microcracks are not or only indirectly recognisable. Signs of microcracks can be so-called slug marks. Check your solar modules for discolouration.

PID effects

PID stands for "Potential Induced Degradation", which roughly translates as "potential-induced degradation". This is a problem that can occur in some solar modules and can impair the performance of the modules. The PID effect occurs when electrical stresses occur between the solar cells and the frame or structure of the solar module. These voltages can be caused by humidity, temperature fluctuations and other factors. Various measures are taken to prevent or minimise the PID effect, including proper earthing of the solar modules, the use of PID-resistant materials and the selection of inverters that can reduce the effect.

  • With our flash tests you can recognise signs of the PID effect.

mobile flash tests

Prevent and recognise defects at an early stage: Arrange a flash test for your solar modules to ensure the performance of your system.


Shading of solar modules can be caused by other buildings and nearby trees, by elements on the building of the solar system (e.g. chimneys), by weather influences, soiling and also by elements on the solar modules (e.g. screws).

The Main problem with the shading of solar modules is the considerable power loss it causes. If parts of one or more solar modules are shaded, energy production can drop dramatically or even come to a complete standstill. As a result, the overall performance of the solar system is significantly impaired, which in turn reduces the economic viability of the system.

Shading can also lead to uneven heating of the solar cells which can lead to thermal stresses and damage. In addition, some conversion systems, such as string inverters, can be even more affected under shading, as they can affect the entire row of modules if a singlemodule is shaded.

  • Shading can be avoided by carefully planning the location of the solar installation. Regular cleaning can also prevent shading.

Wiring error

Wiring faults are a common defect in solar systems and can have a significant impact on performance. They can occur at various points in the electrical cabling of the system.

This can result in physical interruptions or fractures in the connecting cables between the solar modules, the inverters and other components of the system. Interruptions can be caused by various factors such as mechanical stress, rodents or improper installation. Poor connections can also occur if the cables are not properly connected or sealed. This leads to higher electrical resistance and energy losses. Furthermore corrosion at the connection points or cables can impair conductivity and lead to cabling problems.

Wiring faults can lead to considerable performance lossesas the flow of current between the modules and the inverter is impeded. This can lead to uneven energy generation, inefficient utilisation of the solar modules and in some cases even damage to the system.

  • If wiring faults are suspected, they should be rectified as quickly as possible to ensure maximum performance and efficiency of the solar system. 


Delamination means that the layers of a solar module begin to loosen or detach from each other (especially protective layers and front glass). The problem can affect the performance and durability of the modules and usually occurs due to quality problems or unfavourable environmental conditions. Among other things, uneven pressure and moisture can lead to delamination.

  • Delamination can be recognised visually by visible bubbles, cracks or detachments on the surface of the solar modules.


On solar modules it can lead to Discolourations for example to the so-called browning (brownish discolouration) and yellowing (yellowish discolouration). Discolouration can occur for various reasons. For example, exposure to ultraviolet (UV) radiation over a longer period of time can cause the EVA (ethylene vinyl acetate) protective layer in solar modules to turn yellow. If the protective layers or the metal contacts in the solar cells corrode, this can result in browning. Extremely high temperatures, chemical reactions and ageing effects can also change the colour of the solar cells. Discolouration reduces light transmission and thus the ability of the cells to convert sunlight into energy.

  • Discolouration can have different causes. In some cases, it may be necessary to clean or replace the protective coating in order to restore the performance of the modules.

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