Free solar shading analysis

Shading analysis estimates how much energy you lose to shadows before you build. Here are the three sources of shade and how to analyse them without paying for software.

Where shade comes from

• Front rows: the most common loss on ground-mounted plants, largest on winter mornings and evenings. See the row spacing guide.
• Trees and buildings: obstacles on the equator side of the site matter most. Trees grow, so think about their height a few years from now.
• Terrain: hills that block the low sky act like a later sunrise and earlier sunset. Valley sites can lose a lot.

Why shade costs more than you'd think

Panels are wired in series strings, so partial shade on one module can drag down the whole string. The real loss is often bigger than the shaded area suggests, so a good analysis looks at which strings are affected, not only how much area is shaded.

Three free ways to analyse shading

1. Sun path diagram and obstacles

Measure obstacle angles on the horizon and overlay them on a sun path chart. Good for a quick check, but slow, and it doesn't cover row-to-row shading inside the plant.

2. Horizon data from weather tools

Free tools like PVGIS can include the terrain horizon for your location. Useful for mountains, but they ignore your layout, trees and front rows.

3. Full 3D layout simulation

Place the real panel layout on the site, model terrain and nearby obstacles in 3D, and compute shadows for every sun position over a year. Front rows, trees and terrain are all included, which makes it the most accurate. This used to need expensive desktop software; now it runs free in a web browser.

How to read the results

• Annual shading loss (%): the share of energy the whole plant loses to shadows.
• Per-table loss map: a colour map shows which tables to remove or move.
• Season and time: a tree that shades only on winter mornings needs a different answer than one that shades all year.