What are Bifacial Solar Panels?

In the competitive landscape of the UK commercial energy sector, the drive for maximum efficiency and shortened payback periods has brought Bifacial Solar Panels to the forefront.

For UK businesses, the transition from traditional monofacial panels to bifacial technology is one of the most significant upgrades available in 2025. This article explores how this technology works, where it excels in the British climate, and the long-term financial impact on commercial installations.

Unlike standard (monofacial) panels that only capture sunlight on their front-facing surface, bifacial solar panels are designed with solar cells on both the front and the rear.

How They Differ from Earlier Designs

Traditional panels use an opaque backsheet (usually white or black plastic) that blocks any light from reaching the back of the cells. In contrast, bifacial modules use a dual-glass construction or a clear backsheet. This allows them to capture “albedo” light—sunlight that reflects off the roof or ground surface behind the panel.

Why They Excel in the UK Climate

One of the most common misconceptions is that bifacial panels only work in bright, sunny climates. In fact, they are uniquely suited to the UK because:

• Diffuse Light Capture: The UK has a high percentage of overcast days. Bifacial panels are more effective at capturing “diffuse” light (light scattered by clouds) that bounces around the atmosphere and hits the panel from multiple angles.
• Lower Sun Angles: During UK winters, the sun sits low in the sky. Bifacial panels can harvest the light reflecting off surroundings at these shallow angles more efficiently than monofacial designs.¹

Suitable Installation Types: Roof vs. Ground

Bifacial panels are not a “one-size-fits-all” solution. Their performance is heavily dependent on the albedo (reflectivity) of the surface they are installed over.

1. Commercial Flat Roofs

Flat roofs are the most common application for commercial bifacial systems. However, the roof material is critical:

• Best: Light-coloured membranes (white or light grey TPO/EPDM) or roofs treated with reflective coatings.
• Moderate: Standard grey concrete or felt.
• Poor: Dark bitumen or heavily shaded areas.
• Tip: Elevating the panels on a 10–15° pitched racking system is essential. The higher the panel is “lifted” from the roof surface, the more reflected light can reach the underside.

2. Ground-Mounted Systems

Ground-mounted arrays often see the highest “bifacial gain.”

• Ideal Surfaces: Light-coloured gravel, chalky soil, or even concrete hardstanding.
• Agricultural Integration: These are excellent for “Agrivoltaics,” where panels are mounted high enough for grazing or crops underneath, as the open space allows maximum light to circulate to the rear of the modules.

3. Trapezoidal & Standing Seam Metal Roofs

While bifacial panels can be used on pitched metal roofs, the benefit is often lower because the panels sit closer to the metal surface. However, if the metal is highly reflective (e.g., bright aluminium), a modest gain can still be achieved.

Projected Yield and ROI: The 25-Year Outlook

When considering a 25-year commercial investment, the “extra” energy produced by bifacial panels significantly alters the financial modelling.

Average Yield Increase

Based on UK-specific field data, businesses can expect a yield increase of 10% to 20% compared to a monofacial system of the same capacity. In optimal conditions (white reflective roofs or light gravel ground-mounts), this can rise toward 25%.

ROI and Payback Period

While bifacial panels typically carry a 10% to 15% higher upfront cost due to the dual-glass construction and specialized mounting, the increased energy generation usually results in a shorter payback period.

Strategic Insight: Over a 25-year lifespan, a bifacial system effectively provides “bonus” energy for the final 20 years of its life after the initial investment has been recouped. This can represent an additional £50,000 to £100,000 in avoided energy costs for a mid-sized commercial user.

Enhanced Durability and Longevity

Beyond the energy yield, bifacial panels offer operational advantages that protect your investment:

• Glass-on-Glass Strength: The dual-glass structure is more rigid than a plastic backsheet. This makes the panels more resistant to “micro-cracking” caused by wind loading—a common issue on exposed UK commercial rooftops.
• Lower Degradation: Many bifacial manufacturers offer 30-year performance warranties (compared to the standard 25), with lower annual degradation rates (typically 0.4% vs 0.5%).
• PID Resistance: The frameless or specialized designs often used in bifacial modules significantly reduce Potential Induced Degradation (PID), ensuring the system maintains high performance deep into its second decade.

Conclusion: The Expert Verdict

For UK commercial installations where roof space is at a premium or ground-mount space is available, bifacial solar panels represent the “gold standard” for 2025. The combination of higher yields in diffuse light and superior physical durability makes them the most future-proof choice for businesses looking to de-risk their energy costs.

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