Bifacial or monofacial modules? A rooftop decision guide: When bifacial gain pays off on flat roofs and when it does not.
Bifacial modules promise extra yield from rear-side irradiance, but on pitched roofs that promise often evaporates. The rear side needs light, and a dark tile one centimetre from the glass gives it very little.
Where bifacial works
- Flat roofs with white or light membranes and enough clearance height.
- Carports and pergolas with open air on both sides.
- Ground-mounted systems with high albedo surfaces.
For standard pitched-roof work, a good monofacial module is usually the safer specification. Reserve bifacial for projects where the geometry actually feeds the rear side.
| Installation Geometry | Typical Albedo & Rear Clearance | Expected Bifacial Gain (%) & Spec Recommendation |
|---|---|---|
| Coplanar pitched tile roof | Albedo 0.10–0.15; clearance < 10 cm | 0% to +2% optical gain — choose N-Type glass-glass for mechanical rigidity, not rear yield |
| Commercial flat roof (white TPO/gravel) | Albedo 0.50–0.75; tilt 10°–15°, rear height >= 40 cm | +6% to +12% yield — specify Jinko Tiger Neo BDV 590W/635W/720W bifacial modules |
| Solar carport / elevated pergola | Albedo 0.25–0.40; open rear plane (>= 2.2 m height) | +8% to +15% yield — verify inverter MPPT I_sc limit includes 1.15x bifacial factor |
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Author: Virginie Paulo (Senior PV Distribution & Regulatory Specialist) · Technical review: Hendryk Knuth (Technical Director, PV-PARTNER / YOFI SUN S.L.) · Regulatory & technical verification date: 4 November 2026. Prepared with AI-assisted drafting and verified against primary BOE, DGEG, and manufacturer documentation.