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Bifacial Solar Panels: Double-Sided Generation

Updated 2026-03-247 min read

How bifacial panels work

A conventional (monofacial) solar panel has solar cells on the front and an opaque backsheet on the rear. A bifacial panel has solar cells (or at least a transparent or reflective rear surface) on both sides, allowing it to capture light from both directions.

The front generates electricity from direct and diffuse sunlight, just like any panel. The rear generates from albedo — light reflected off the ground, roof, or surrounding surfaces that reaches the back of the panel.

The key to bifacial performance is what's behind and beneath the panel. A white roof or light-coloured surface reflects much more light to the rear cells than dark roof tiles or tarmac.

Where bifacial gains come from

The additional generation from the rear side depends on several factors:

Surface reflectivity (albedo)

Surface	Albedo (reflectivity)	Estimated bifacial gain
Fresh snow	80–90%	20–30%
White membrane roof	60–80%	15–25%
Light gravel	40–60%	10–20%
Light concrete	30–50%	8–15%
Green grass	15–25%	5–10%
Dark roof tiles	5–15%	2–5%
Black tarmac	5–10%	1–3%

Mounting height

The higher the panel is above the reflecting surface, the more reflected light can reach the rear. Panels flush-mounted on a roof with minimal gap receive almost no rear illumination. Panels elevated 0.5–1m on a ground mount receive significantly more.

Tilt angle and row spacing

Bifacial panels perform better at steeper tilt angles and with wider row spacing (in ground-mount arrays), which allows more light to reach the rear surface.

Bifacial on a UK pitched roof

Here's the honest assessment: most UK pitched-roof installations won't see meaningful bifacial benefit.

The reasons:

Minimal gap — panels are typically mounted 10–15cm above roof tiles on standard rail mounting. This tiny gap allows very little reflected light to reach the rear.
Dark surfaces — most UK roofs are slate or dark tile, with low albedo. There's simply not much light to reflect.
Shading from the roof — the roof surface beneath the panel is in the panel's own shadow for most of the day, further reducing rear illumination.

Realistic bifacial gain on a typical UK pitched roof: 2–5%, possibly less. At a panel premium of 10–20%, the maths doesn't work.

Marketing hype vs reality

Some panel manufacturers heavily promote bifacial technology, quoting gains of "up to 30%". These figures come from ideal conditions — elevated mounting over white surfaces in sunny climates. On a UK roof with dark tiles, expect a fraction of these claims. Don't pay a premium based on best-case marketing numbers.

Where bifacial panels do make sense

Ground-mounted systems

This is where bifacial panels genuinely earn their keep. A ground-mounted array elevated 0.5–1m above grass or light-coloured surface can achieve 8–15% bifacial gain. If the ground is covered with white gravel or a reflective membrane, gains of 15–25% are realistic.

For UK farms, commercial sites, or large gardens with ground-mounted solar, bifacial panels are worth the modest premium.

Flat commercial roofs

Large flat roofs with white waterproof membranes are excellent for bifacial panels mounted on tilted frames. The white surface reflects light to the rear, and the mounting framework provides the necessary elevation. Commercial installations on warehouse and industrial roofs increasingly use bifacial panels for this reason.

Canopies and carports

Solar canopies over car parks or driveways are elevated well above the ground surface. Light concrete or tarmac beneath provides albedo, and the elevation allows ample rear illumination. Bifacial panels make excellent carport coverings.

Vertical installations (east-west facing)

An emerging niche: bifacial panels mounted vertically on fences, walls, or purpose-built frames, oriented east-west. The front captures morning sun, the rear captures afternoon sun (or vice versa). This produces a generation profile that better matches morning and evening demand, and can achieve surprisingly good annual yields.

Bifacial + tracker = maximum gain

The highest bifacial gains come from single-axis tracker systems in ground-mounted arrays. The tracker follows the sun, and the rear side picks up ground-reflected and diffuse light throughout the day. This is a commercial/utility-scale solution, not residential, but it demonstrates the technology's potential.

Bifacial panel options in 2026

Large solar farm with rows of panels catching sunlight — Bifacial panels deliver their best gains in ground-mounted and elevated installations

Most tier-1 panel manufacturers now offer bifacial variants of their flagship models. The bifacial version typically uses a transparent glass or clear backsheet instead of an opaque white one.

Common bifacial panels available in the UK:

Trina Solar — Vertex S+ bifacial variants
Canadian Solar — HiKu and BiHiKu range
LONGi — Hi-MO series with bifacial options
JA Solar — DeepBlue bifacial variants

The price premium for bifacial is typically 5–15% over the equivalent monofacial panel. In a competitive market, some bifacial panels are priced at parity with monofacial.

The cost-benefit calculation

For a pitched UK roof installation:

Panel premium: ~£20–£40 per panel extra for bifacial
System cost increase: £160–£500 for a 10-panel system
Extra generation: 2–5% = roughly 80–200 kWh/year more from a 4kW system
Extra income/savings: £20–£60/year
Payback of premium: 3–15 years

It's not terrible, but it's not compelling either. The same money invested in one or two extra monofacial panels would produce more additional electricity.

For a ground-mounted installation:

Extra generation: 10–20% = 400–800 kWh/year more
Extra income/savings: £100–£240/year
Payback of premium: 1–3 years

Now the maths works.

Should you choose bifacial?

Yes, if:

You're installing a ground-mounted system
Your flat roof has a light-coloured surface
You're building a solar carport or canopy
Bifacial panels are available at the same price as monofacial (increasingly common)

Probably not, if:

You have a standard UK pitched roof with dark tiles
Panels will be flush-mounted with minimal gap
You're paying a significant premium for bifacial

If your installer offers bifacial panels at no extra cost (or a trivial premium), take them — even a 2–3% gain is free energy. But don't pay a meaningful premium for bifacial on a dark pitched roof. The physics simply don't support the investment.

5–25%

extra generation in ideal conditions

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For standard UK rooftop installations where bifacial gains are minimal, these monofacial panels offer the best value: