The ones installed on houses are especially vulnerable because the crap falls out of the sky as dust, too. The dust covers the panels and occludes the cells. Then, they don’t generate the possible electricity. The whole thing is a scam, both coming and going. Crap in the sky, panels that don’t generate! 

Rothbardian_fanatic

conspiracy

There's a Bit of Truth To Some Climate Conspiracy Theories.

Imyourfed

hahaha. I remember having seen advertisements with people showing how they set up solar panels in shadows of trees in a big city.
To be honest I am quite a solar panel proponent as I used it for camping and my battery has been useful after an earthquake as well.
But sometimes I see houses with solar panels with a shadow from the neighboring house... And I know that when there is a small shadow on a cell, the whole row produces negligible electricity, so their installation must be bad.