1. Distinguish bifaciality from module construction
Check the model’s front-side power, bifaciality factor and materials. The bifaciality factor compares both faces under reference conditions; it does not measure annual gain on your roof. Glass-glass construction and bifacial capability describe different properties. Read load ratings and warranties separately.
2. Document rear-side illumination
Record height, spacing, tilt, ground conditions and obstacles. Albedo describes ground reflectance and varies with surface condition and season. Rails, cables and rows can obstruct rear-side light. Ask for the assumptions and simulation limits, particularly on a confined roof or with several orientations.
3. Assess snow and availability separately
Ask how the simulation accounts for ground snow, covered modules, the mountain horizon and downtime. Compare monthly kWh before concluding that winter generation improves. Vertical mounting changes exposure and snow deposition but does not establish snow-free or loss-free operation. Plan access, inspection and roof-snow hazards with professionals.
4. Compare structural requirements and the full budget
Have snow and wind loads assessed for the site, building and mounting system. A module data-sheet rating does not validate the entire structure. Compare options by area, capacity, monthly generation, mounting, access and service. Value energy using your consumption and tariffs; an advertised bifacial gain does not establish profitability or self-sufficiency.