Solar Bifacial Gain Calculator

Rear irradiance (estimated option)

• Rear view factor is approximated from tilt, height, and row spacing (bounded 0.05–0.95).
• Rear irradiance = Front × Albedo × RearViewFactor × (1 − RearShadingLoss).

Bifacial gain

• Rear-to-front ratio = Rear / Front
• Gain (%) = Bifaciality × (Rear / Front) × 100

Power estimate (comparative)

• Effective irradiance = Front + (Bifaciality × Rear)
• Temperature multiplier = 1 + (TempCoeff/100) × (CellTemp − RefTemp)
• Net loss multiplier = Π(1 − Loss%/100)
• DC kW = (ModulePower × Modules / 1000) × (EffectiveIrr/1000) × TempMult × LossMult
• AC kW = DC kW × (InverterEff/100)

1. Pick a rear irradiance method: estimated for early planning, measured for sensor-based validation.
2. Enter front irradiance and either rear irradiance or albedo plus geometry inputs.
3. Set bifaciality and rear shading loss to reflect module type and mounting constraints.
4. Add losses and temperature assumptions to match your site maintenance plan and operating climate.
5. Click Calculate. Review gain, effective irradiance, and DC/AC estimates.
6. Use Download CSV or Download PDF to archive assumptions in reports.

1) Why bifacial gain matters on construction sites

Bifacial modules harvest light from both faces, so site layout and ground conditions directly affect delivered power. Temporary yards, rooftops, and containerized plants often change surface reflectance and shading throughout a project. A quick gain estimate helps compare racking options, decide whether to raise modules, and justify surface preparation.

2) Key inputs that drive rear contribution

Front irradiance represents the available solar resource, while albedo captures how much light the ground reflects. Tilt, height, and row spacing influence how much of that reflected light reaches the rear of the module. Rear shading loss accounts for structural members, adjacent rows, and any obstructions behind the array.

3) Turning irradiance into bifacial gain

The core output is bifacial gain percentage: bifaciality multiplied by the rear-to-front irradiance ratio. If rear irradiance is measured, the result becomes a field-calibrated indicator for that exact location. If rear irradiance is estimated, the geometry-based view factor provides a practical planning approximation.

4) Losses and temperature effects you should include

Soiling, mismatch, wiring, and light-induced degradation reduce delivered DC power and can vary by site practices. Temperature coefficient adjusts module output when cell temperature differs from the reference condition. Including inverter efficiency converts DC estimates into an AC value suitable for equipment sizing and reporting.

5) Using results for layout and procurement decisions

Use gain and effective irradiance to compare alternatives such as higher clearance, wider pitch, or improved ground finish. Pair AC estimates with inverter limits and cabling plans to avoid clipping and unexpected voltage drop. Exported CSV/PDF outputs document assumptions for stakeholders, bids, and commissioning checklists.

1) What is bifacial gain in this calculator?

Bifacial gain is the percent uplift from rear-side irradiance, calculated as bifaciality times rear-to-front irradiance ratio. It helps compare bifacial versus monofacial performance under the same conditions.

2) When should I choose the measured rear option?

Select measured when you have rear irradiance sensor data or a validated model output. It reduces uncertainty and better reflects local shading, surface reflectance, and mounting constraints.

3) How does albedo influence the result?

Albedo represents ground reflectance. Higher albedo generally increases rear irradiance and gain. Surface choices like gravel, light membranes, or snow can change albedo significantly.

4) What does rear shading loss include?

Rear shading loss captures blocked rear light from racks, torque tubes, obstructions, and adjacent rows. Use higher values for tight pitches, heavy structural members, or cluttered back-of-array areas.

5) Why include temperature coefficient and cell temperature?

Module output decreases as cell temperature rises for most silicon modules. The calculator uses the coefficient and the temperature difference from the reference to adjust DC power estimates.

6) Are the DC and AC values energy or power?

They are instantaneous power estimates at the provided irradiance and temperature, not annual energy. Use them for sizing comparisons; annual yield requires hourly weather data and a full simulation.

7) What is a typical bifaciality factor?

Many commercial bifacial modules fall around 0.65 to 0.75, but it varies by product. Use the manufacturer’s bifaciality rating for the module family you plan to procure.