If there is something between the sun and your panels, that's another story. Solar panels in shade
produce much less energy, because solar cells in a panel are interconnected. If the performance of one cell goes down, the ability to produce electricity of the whole module suffers. The performance of a panel may fall by more than 75%. Constant shading also shortens the lifespan of modules, because some cells have to work more than others and eventually burn out. Manufacturers addressed the problem of shading by implementing bypass diodes into PV modules. They split panels into several sectors, normally 3 or 4. If a cell in one sector is shaded, diodes don't let it influence the other sectors. For example, Panasonic HIT 330W
with 4 bypass diodes will lose only 25% of its power output if one cell gets shaded. A solar panel with 3 diodes would lose a third of its production.
A shaded panel can become a problem if modules are connected in series and a string inverter is used. Bad performance of one panel drags down the power output of others. To avoid it, you can use microinverters
instead, or combine a string inverter with power optimizers
for every panel in the string.