The Devastating Effects of Shade On Solar Panels

Even small amounts of shade can cause major power interruption in a solar array. If you shade only one cell in a module you will likely see a 33% power reduction from that module. If you shade a row of cells in one module, you will see a devastating 90% power reduction. The even bigger problem is that every module in the series string will see the same power reduction. So when that chimney casts a shadow over one row of cells on the last module in a string of 13, you lose 90% of the power to ALL 13 modules

Micro-Inverters (like Enphase) and the National Semiconductor SolarMagic control can help minimize the power loss due to shading, but solar pros agree that every effort should be made to ensure ALL modules are shade free between the hours of 9AM and 3PM.

Even shadows from power lines and bird poop (especially pigeons!) can cause a noticeable power reduction. (AEE Solar)