Bifacial solar panels are now the dominant technology shipped globally — BloombergNEF reported that bifacial modules represented over 70% of new panel shipments in 2025. The technology is well proven. The marketing around bifacial gain, however, often overstates what homeowners and commercial buyers can realistically expect.
How Bifacial Gain Actually Works
Bifacial gain is the additional energy yield from the rear face expressed as a percentage of the front-face-only yield. It depends on three variables:
- Albedo — the reflectivity of the surface beneath the panels (grass, concrete, white membrane, snow, sand)
- Ground clearance — how high the panel sits above the reflecting surface
- Tilt angle — steeper tilts allow more reflected light to reach the rear
High albedo + high clearance + high tilt = maximum bifacial gain. Low albedo + low clearance + shallow tilt = minimal gain.
Bifacial Gain by Mounting Type
Flush Residential Rooftop (< 10 cm clearance)
This is the most common residential installation worldwide and the worst case for bifacial gain. With tiles or asphalt shingles just centimetres below the rear of the panel, almost no reflected light reaches the rear face. Independent studies from Fraunhofer ISE and NREL consistently measure rear-side contribution of 0–3% in this configuration.
Practical bifacial gain: 0–3%
For flush rooftop installs, bifacial panels offer no meaningful advantage over comparable monofacial panels. The value proposition for bifacial here is that the same production line now ships bifacial panels at no price premium — so you get future optionality if the mounting situation ever changes.
→ Numbers speak louder: calculate your annual solar return and take the guesswork out.
Raised Rooftop (> 15 cm clearance, light-coloured roof)
With increased clearance and a reflective roof membrane (white TPO or EPDM is common in commercial flat-roof installs), bifacial gain improves meaningfully. A white TPO membrane has an albedo of 0.65–0.80 compared to 0.10–0.20 for dark asphalt.
Practical bifacial gain: 4–8%
Ground Mount (standard soil or grass)
Ground-mounted systems with 0.5–1.0 m clearance over typical green grass (albedo 0.20–0.25) show measurable rear-side contribution. NREL field data from utility-scale systems in the United States shows 6–9% bifacial gain in this configuration under standard single-axis tracker geometry.
Practical bifacial gain: 5–10%
Ground Mount Over High-Albedo Surface
Installations over gravel, light sand, concrete, or deliberate white ground cover significantly increase rear irradiance. Albedo values of 0.35–0.50 are achievable. This configuration is increasingly used in utility-scale solar farms where ground material is chosen specifically to enhance bifacial yield.
Practical bifacial gain: 10–18%
Single-Axis Trackers
Single-axis trackers that follow the sun through the day also rotate panels away from shading each other's rear faces. This, combined with ground clearance, is the configuration that achieves the highest bifacial gains in field data. IEA PVPS Task 13 reported median bifacial gains of 8–15% for tracker-mounted bifacial systems in mid-latitude sites.
Practical bifacial gain: 8–15%
Carport and Shade Structures
Bifacial panels used in carport canopies sit over vehicle surfaces with variable albedo — white or silver vehicles contribute meaningfully, while black vehicles absorb light. In practice, carport bifacial gain averages 3–7% given the mix of vehicle colours and frequent shading from vehicles' own height.
Practical bifacial gain: 3–7%
Agrivoltaic (Elevated Agricultural Systems)
Agrivoltaic systems mount panels at 3–4 m height over agricultural land, allowing crops to grow beneath. The elevation maximises rear-side irradiance. Grain crops and cover vegetation have albedo values of 0.18–0.25. Bare soil is lower (0.10–0.15), but the elevation height compensates. Real installations in France and Japan report 8–12% bifacial gain.
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Practical bifacial gain: 8–12%
Comparison: Bifacial Gain by Configuration
| Mounting Type | Albedo Below | Clearance | Typical Bifacial Gain |
|---|---|---|---|
| Flush rooftop (dark tile) | 0.10–0.15 | < 10 cm | 0–3% |
| Raised flat roof (white membrane) | 0.65–0.80 | 15–30 cm | 4–8% |
| Ground mount (grass) | 0.20–0.25 | 0.5–1.0 m | 5–10% |
| Ground mount (gravel/concrete) | 0.35–0.50 | 0.5–1.0 m | 10–18% |
| Single-axis tracker (mixed) | 0.20–0.35 | 0.6–1.0 m | 8–15% |
| Carport | 0.15–0.40 | 2.0–3.0 m | 3–7% |
| Agrivoltaic | 0.15–0.25 | 3.0–4.0 m | 8–12% |
Modelling Bifacial Yield Accurately
Design software tools including PVsyst (version 7.4+), PVWatts (NREL), and Solarius PV now include bifacial gain models that account for albedo input, row spacing, and clearance height. If your installer is quoting bifacial gain without using one of these tools, treat the estimate with scepticism.