How Shading Affects Solar Panels
Shading is the silent killer of solar production. Even a small shadow across one panel can reduce your entire system's output.
Why Shading Matters So Much
Solar panels are wired in series — like old Christmas lights. When one cell is shaded, it becomes a bottleneck for the entire string. A shadow covering just 10% of one panel can reduce that string's output by 30–50%.
This is because the shaded cell can't produce current, and since electricity flows through the whole string, it limits every panel connected to it.
Common Shading Sources
- Chimneys and vents — cast moving shadows throughout the day
- Trees — the most common culprit, especially deciduous trees that grow over time
- Neighboring buildings — particularly in urban areas
- Satellite dishes and antennas — small but can shade nearby cells
- Roof ridges — on complex roof shapes, one section can shade another
Time-of-Day Shading
A shadow that only appears for 1–2 hours in early morning or late afternoon has minimal impact. The critical hours are 10:00–15:00, when the sun is highest and panels produce the most.
Seasonal variation matters too — a nearby building might not shade your roof in summer (high sun angle) but could in winter (low sun angle).
Solutions
Microinverters — instead of one inverter for all panels, each panel gets its own. A shaded panel only affects itself. Costs 20–30% more but eliminates string-level losses.
Power optimizers — a middle ground between string inverters and microinverters. Each panel gets an optimizer that maximizes its individual output while still using a central inverter.
Panel placement — a good installer will avoid placing panels in known shade zones, even if it means fewer panels overall.
Tree trimming — sometimes the simplest solution. A professional arborist can selectively trim branches without removing trees.
Should I Worry?
If your roof gets full sun between 10:00 and 15:00 for most of the year, shading won't significantly affect your system. Our solar calculator uses satellite data that accounts for typical obstructions in your area.