{"id":600,"date":"2025-10-30T09:11:25","date_gmt":"2025-10-30T08:11:25","guid":{"rendered":"https:\/\/blog.fronius.com\/solar-energy\/2025\/10\/30\/shade-encroaching-on-pv-systems-is-it-a-problem-of-the-past\/"},"modified":"2026-03-10T09:29:27","modified_gmt":"2026-03-10T08:29:27","slug":"shade-encroaching-on-pv-systems","status":"publish","type":"post","link":"https:\/\/blog.fronius.com\/solar-energy\/en\/know-how\/shade-encroaching-on-pv-systems\/","title":{"rendered":"Shade encroaching on PV systems\u2014is it a problem of the past?"},"content":{"rendered":"\n

More sun equals more solar power. Anyone planning their own PV system on the roof should look into the best conditions for their installation, to make sure the system works perfectly and generates optimum yields. The shading of solar modules continues to be one of the main factors preventing this, although smart developments on the solar market have started to cast shade on this issue. Read on to find out why the partial shading of solar modules now only has a negligible effect on a photovoltaic system\u2019s yield.  <\/strong><\/p>\n\n\n\n\n\n\n\n

Bright sunshine, not a cloud in the sky, and a PV system on the roof\u2014these are the ideal conditions for producing as much solar energy as possible for the home. But very few roofs are completely free of shade.
Trees, masts, house antennas, and neighboring buildings often cast shadows on solar modules, supposedly resulting in a lower output and yield. However, a closer look shows that irregular shading only has a minor effect on the total yield of your PV system over the course of the year; what really counts is choosing the right inverter and opting for the correct solar module design. This is where the so-called FC factor comes into play:<\/p>\n\n\n\n

<\/div>\n\n\n\n

What is the FC factor?<\/strong><\/h4>\n\n\n\n

The FC factor<\/strong> (also known as the shading loss factor<\/strong> or derating factor for shading<\/strong>) describes the influence of shading<\/strong> on the performance of a PV system<\/strong>.

The fill correction factor (FC factor) indicates the extent to which a shaded solar module\u2019s actual output is reduced compared to the output without shading, and is calculated using software-supported simulations or on the basis of empirical values and calculation tables.

The shading loss factor is used in the yield forecast and in particular when planning complex PV systems to calculate realistic values for the energy yield. It takes into account the orientation and inclination of the solar modules, as well as their interconnection and the type of shade (e.g., localized spots of shade, shading across a larger surface area, temporary shade).

It is usually specified as a percentage or a dimensionless value between 0 and 1.

FC = 1 \u2192 no shading, full output

FC < 1 \u2192 shading is present, reduced output

For example, if a solar module is partially shaded by a tree and can therefore only produce 80% of its original output, the FC factor is 0.8. However, it\u2019s possible to get around this issue\u2014read on to find out how!<\/p>\n\n\n\n

<\/div>\n\n\n\n

A stubborn myth disproved<\/strong><\/h3>\n\n\n\n

\u201cIf solar modules are shaded (for example by leaves), this means that the entire PV system is no longer able to produce power, or can only produce very little power. It\u2019s like a garden hose that outputs no or very little water, regardless of where it is kinked.\u201d<\/em>  <\/p>\n\n\n\n

This claim is still widespread, but has long been outdated because the solution is already integrated in every solar module\u2014in the form of bypass diodes.<\/p>\n\n\n\n

<\/div>\n\n\n\n

Hitting the target with bypass diodes<\/strong><\/h3>\n\n\n\n

Today, a modern photovoltaic module is generally equipped with bypass diodes, which serve as bridging devices: if certain areas of a solar module are unable to deliver full power\u2014for example due to shading or soiling\u2014bypass diodes ensure that the current bypasses the affected cell strings.
So exactly does this work? Changing the DC voltage of the inverter, which is applied to the string, activates the bypass diodes making them conductive; the affected cell string of the affected PV module is thereby bridged.<\/p>\n\n\n\n

This means<\/strong> the other module areas remain fully operational and the entire system can continue to work efficiently.  \u201cThis has two advantages,<\/em>\u201d explains Marija Milosavljeva, Product Manager at Fronius. \u201cOn the one hand overheating and possible hot spots are prevented, while on the other hand a profitable yield is generated despite partial shading<\/em>.\u201d<\/p>\n\n\n\n

Improvements on the solar module market <\/strong><\/h3>\n\n\n\n

Ongoing developments in solar modules are also helping to make the photovoltaic system on your roof even more cost effective: <\/p>\n\n\n\n

Thanks to half-cell technology\u2014i.e. halving the individual solar cells\u2014conventional half-cell modules can not only reduce power losses, but also make better use of the light. This enables module operation to remain stable even at high temperatures.<\/p>\n\n\n\n

Furthermore, shading behavior is also better with half-cell modules: bypass diodes divide the solar modules in the middle. This means that if the lower or upper half of the half-cell module is shaded by leaves, for example, the other half of the module can still deliver full power. By comparison, if a full-cell module were to be shaded in exactly the same way, the output of the entire solar module would be lost.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n
<\/div>\n\n\n\n

Efficient MPP solar trackers for more power <\/strong><\/h3>\n\n\n\n

In order to keep shading losses or mismatch losses as low as possible, string or multi-string inverters are equipped with one or more MPP trackers (Maximum Power Point Trackers). Ideally, one MPP tracker is used per string; this continuously determines the optimum operating point of the connected strings and in doing so maintains the maximum power of the PV system at all times. <\/p>\n\n\n\n

Complete with shading management<\/strong><\/h3>\n\n\n\n

Maximum yield despite partial shading? Smart shading management, which is ideally already integrated in the inverter, is able to ensure this; meaning that even roof surfaces with partial shading can be optimally configured. <\/p>\n\n\n\n