Why it matters on a Mauritian roof.
Same shade. Different loss.
A water tank, a parapet or a dish shades part of the roof every day. On a standard panel, one shaded cell switches off the whole third of the panel it sits in. On back contact, only the shaded cells stop.
Drag the shadow across the panels.Move the shadow with your finger.
Simplified: 60-cell panels, a shaded cell counted as fully lost.