Partial shading is the most performance-damaging condition in solar PV systems — and it is more common in Philippine urban settings than most installers admit. Water tanks, clotheslines, satellite dishes, trees, and neighboring buildings all create shade. Here is how to address it properly.
In a series string, current is limited by the weakest panel. One panel at 50% output = the entire string drops toward 50% output. With bypass diodes (standard in all modern panels), the shaded panel is bypassed — but its power contribution is lost entirely.
Example: 10-panel string, 1 panel in shadow → string output drops 10-15% even with bypass diodes active.
| Solution | How It Helps | Additional Cost | Best For |
|---|---|---|---|
| Panel layout redesign | Eliminate shade by repositioning panels | ₱0 (design change) | Shade source is fixed and predictable |
| DC power optimizers | Each panel has MPPT optimizer — shaded panel doesn't drag string | ₱3,000–5,000 per panel | Partial/intermittent shading on some panels |
| Microinverters | Each panel independent — complete isolation | Doubles system cost | Complex shading on multiple panels |
If your inverter has two MPPT inputs — most modern inverters do — shade-affected panels can be put on a separate string from unshaded panels. The shaded string underperforms, but the main string operates at full power. Cost: ₱0 (just a wiring change during installation).
Request a proper shade analysis from installers at solarenergyph.shop before committing to a design.
Engr. Jason Morales — Founder, SolarEnergyPH