Panel Shading Tools

Your solar provider should provide a very thorough analysis of your roof and near-by obstructions before you accept your contract. There are many websites that list tools and calculations. I found PVResources to be quite handy. [There is actually a lot of info on PVResources.]

There are some very handy tools to use, the primary one is the Solar Pathfinder. A solar installer would be able to provide a quantitative analysis of your roof and show you the areas that would be affected by shade.

Another interesting tool by Sustainable by Design that I found quite helpful was for tilted panels on flat roofs. I am sure you could use it on a sloped roof to estimate the impact of obstructions too. But I found it equally interesting to see the impact on our roof. See below! We don't have any obstructions from trees, etc. You can see with the white blocks our panels are fully illuminated, but after 4 or 5 pm the sun has gone far enough westward that it no longer strikes our SE facing panels.