Bifacial modulePanel producing on both sides

Bifaciality comes from using a transparent (glass-to-glass) or semi-transparent backsheet instead of an opaque backsheet. The bifaciality factor (BF) expresses what fraction of the front power can be produced by the rear face: BF = 70-80% for most TOPCons. The actual gain depends on the albedo (reflectivity) of the surface under the panel: snow (0.8-0.9) >> white concrete (0.25-0.35) > grass (0.15-0.25) > bitumen roof (0.05-0.10). In standard residential roof installation (dark roof, limited space), the bifacial gain is often negligible (1-3%). It is when installed on the ground, on white gravel or snow, that the gain is significant (10-25%).

In Switzerland, bifaciality is especially relevant for agricultural (agrivoltaic) or gravel ground installations. For standard residential roofs, the real gain is 1-5% — interesting but not decisive in the choice. Valais snow in winter is a special case: the high albedo of the snow can boost rear face production by 8-15% during snowy months.