What Is a Shade Analysis?

Shade is not a single yes or no. The sun sits low in winter and throws long shadows, so a tree that is harmless in July can cut deeply into December production. Remote tools build a three-dimensional model of the house and its surroundings from imagery or aerial scans and simulate the sun’s path. An on-site tool takes a fisheye reading from the roof and maps obstructions against the sun’s path for each month. Either way, the output is the share of sunlight available, usually per roof section.

The result decides where panels go and where they do not. Heavily shaded sections get skipped, partly shaded ones may call for panel-level electronics, and the loss is built into the production estimate. On the phone, the question is simple: are there tall trees or buildings close to the house, and which side of the roof do they shade? Homeowners who say they will trim the tree are making a promise that the design cannot count on until the work is done.

Shade analyses fail in predictable ways. Satellite models miss new construction, recently grown trees, and small obstructions like vents. Seasonal swings catch people out, since photos taken in summer can hide winter shadows. And trees keep growing: a roof that passes today may not in a few years. A prospect who insists the roof has no shade usually means no shade at the hour they checked.