Bird droppings create what is termed ‘hard shading’ on solar panels. Hard shading is when a solid object or obstacle is placed over a solar panel, blocking the light in a clear, definable shape. It is different from ‘soft shading’ which is created from dust build-up, or an overhanging tree branch.
Hard shading is particularly damaging to the output of solar panels because it can cause the current cannot flow through the shaded area efficiently which makes it bunch up and flow through the unshaded part of the cell. This creates an extreme temperature increase, resulting in the dreaded ‘hotspots’ that are damaging to solar panels. Hotspots lower the power output of the whole panel. Partial shading of even one cell on a solar panel will reduce its power output. The best way to avoid power output drops is to avoid shading whenever possible. Here is a very useful in-depth article about the effects of hard shading if you would like a more detailed explanation.
This is why in some instances it is important to combine bird deterrents on your solar panels as well as solar panel cleaning. Clean Solar Solutions have been called in to clean solar panels where bird droppings have caused a whole array to drop its output by over 25%, solely because of seagull droppings. We have subsequently cleaned the solar panels and restored the output.