Bifacial solar panels generate electricity from both the front and rear of the cell, using a transparent or semi-transparent rear layer instead of the opaque backsheet found on standard panels – this deep-dive covers how the technology itself works, the different cell and construction types available, and where it’s actually being deployed in the UK today, from solar farms to commercial rooftops.
How Bifacial Solar Cells Are Built
Most bifacial panels use PERC (Passivated Emitter and Rear Cell) or newer TOPCon cell architecture, both of which allow light to be captured and converted on the rear surface of the cell rather than being blocked by a solid metal backing. The panel itself is usually built with dual glass – a sheet of tempered glass on both the front and rear, sandwiching the cells between them – rather than the glass-front, polymer-backsheet sandwich used in most monofacial panels. This dual-glass build is also why bifacial panels tend to be heavier and, generally, more resistant to moisture ingress and UV degradation over the long term.
Types of Bifacial Panel Construction
The table below sets out the main construction variants found in bifacial panels on the market.
| Construction Type | Description | Typical Use |
|---|---|---|
| Dual-glass, framed | Glass front and rear, standard aluminium frame | Residential and commercial rooftops |
| Dual-glass, frameless | Glass front and rear, no frame – reduces shading at panel edges | Ground-mount solar farms |
| Transparent backsheet (non-glass) | Lighter-weight polymer rear layer, partially transparent | Lightweight or portable applications |
| Bifacial with tracking mount | Panel mounted on a system that follows the sun | Utility-scale solar farms (maximises rear-side gain) |
Where Bifacial Panels Are Actually Being Used in the UK
Bifacial technology has become close to a default choice on new UK utility-scale solar farms, where panels are mounted on frames well above grass or gravel, giving the rear surface genuine reflected light to work with – UK ground-mount solar farms commissioned in the past few years increasingly specify bifacial as standard rather than as a premium upgrade. On the commercial side, bifacial panels turn up most often on flat warehouse and distribution centre roofs finished with a light-coloured membrane, and on solar carports, where the open structure beneath the panel gives the rear side room to capture reflected light from the ground or parking surface below.
What the “Bifaciality Factor” on a Datasheet Means
Panel datasheets often quote a bifaciality factor, usually expressed as a percentage between 65% and 90%, representing how much power the rear side generates relative to the front under identical light conditions. A panel with a 75% bifaciality factor generating its full rated output from the front and receiving strong reflected light on the rear could theoretically add up to 75% of its front-side output from the back – in practice, real-world albedo and mounting geometry mean actual gains are almost always well below that theoretical ceiling, which is why the 5-45% real-world gain range quoted by installers is a far more useful figure than the bifaciality factor alone.
Durability Advantages That Come With Bifacial Construction
Beyond the extra energy capture, the dual-glass build common to most bifacial panels offers genuine durability benefits independent of the bifacial effect itself – better resistance to potential-induced degradation (a slow performance loss caused by voltage stress in humid conditions), improved fire resistance compared with polymer-backed panels, and typically a slightly better warranty as a result. Some installers now specify bifacial panels on UK rooftop jobs purely for this durability advantage, even where the albedo beneath the panel is too low to deliver much rear-side generation gain.
Frequently Asked Questions About Bifacial Solar Panels
What is a good bifaciality factor for a solar panel?
A bifaciality factor of 70% or higher is generally considered strong, with premium panels reaching up to 90%. That said, the bifaciality factor only describes the panel’s theoretical rear-side potential – the actual gain you see depends much more on mounting height, spacing and the albedo of the surface beneath the panel than on the datasheet figure itself.
Can bifacial panels be installed flush against a roof like a normal panel?
Yes, they can be installed flush, but doing so largely defeats the purpose – with no gap for reflected light to reach the rear surface, a flush-mounted bifacial panel performs close to how a monofacial panel of the same front-side spec would. Genuine bifacial gains require some clearance and a reasonably reflective surface underneath, which is why they’re most effective on elevated ground-mount frames rather than roofs.
Do bifacial panels still work well in typical cloudy UK weather?
Yes – bifacial panels generate front-side power the same way monofacial panels do regardless of weather, and diffuse light on overcast days is actually reflected fairly evenly in all directions, which can help rear-side capture proportionally more than on a bright, directly sunny day. The technology isn’t weather-dependent in any way that makes it less suited to the UK climate specifically.
Do bifacial panels last longer than standard panels?
Often yes in practice, mainly because the dual-glass construction common to bifacial panels resists moisture ingress and potential-induced degradation better than the glass-and-polymer-backsheet design used in most standard panels. Manufacturer warranties reflect this too, with many bifacial models now carrying 30-year product warranties compared with the 25-year standard still common on conventional panels.
For a direct comparison against standard monofacial panels, including UK-specific albedo data, see our guide on bifacial vs monofacial solar panels.
