Shading
Partial or complete shading of solar modules by trees, buildings, or other obstacles.
Also known as: Partial Shading, Shadow Casting
What Is Shading?
Shading refers to the partial or complete blocking of sunlight on solar modules, which reduces electricity yield. Even small shadows can cause disproportionate losses in series-connected modules, as the weakest cell limits the current of the entire string.
Causes
- Buildings and structures: Neighbouring houses, chimneys, antennas, dormers
- Vegetation: Trees, hedges (seasonally variable)
- Self-shading: Tilted module rows shading each other
- Temporary shading: Leaves, snow, bird droppings
- Horizon: Mountains, hills
Impact on Yield
| Scenario | Yield Loss |
|---|---|
| Small shading (1 cell) | 5—30% of the module |
| One third of the module shaded | ~33% (with bypass diode) |
| Entire string shaded | Up to 100% of the string |
| Persistent shading | Cumulative annual losses |
Countermeasures
- Planning: Shading analysis before installation (e.g. with a sun path diagram)
- Microinverters: Each module operates independently
- Power optimisers: Module-level optimisation on a string inverter
- Module placement: Avoid shaded areas
Practical Tip
A shading analysis before installation is essential. Even small obstacles (antenna, cable duct) can cause unexpectedly high losses. Tools like PV*SOL simulate shadow casting throughout the entire year.
Related Terms
Bypass Diode
Protective component in a solar module that routes current around shaded cells to prevent power loss and hot spots.
Microinverter
Small inverter mounted directly on a single solar module, converting DC to AC on a per-module basis.
MPP Tracker
Electronic control in the inverter that continuously finds and optimises the Maximum Power Point of the solar modules.
String Inverter
Central inverter that converts the direct current from one or more series-connected module strings into alternating current.