One of the biggest questions people ask when considering bifacial solar panels UK installations is how much electricity they can actually produce.
Bifacial panels have an important advantage over traditional monofacial modules: they can generate electricity from both the front and rear surfaces. This means they can potentially produce additional energy from sunlight reflected towards the back of the panel.
However, the amount of additional energy generated can vary considerably depending on the installation.
What Is Bifacial Gain?
Bifacial gain refers to the additional energy generated by the rear side of a bifacial solar panel compared with the energy generated from the front side alone.
For example, if a bifacial panel produces its normal output from the front and then generates additional electricity from reflected light reaching the rear, that extra production represents its bifacial gain.
It is important to understand that there is no single percentage of additional generation that applies to every UK installation.
The actual result depends on the conditions surrounding the panels.
How Much Can Bifacial Solar Panels Generate?
The total electricity generated by a bifacial system depends on several factors, including:
- Panel wattage
- Panel efficiency
- Location in the UK
- Roof or ground conditions
- Panel orientation
- Tilt angle
- Shading
- Surface reflectivity
- Panel height
- Row spacing
- Weather conditions
A well-designed bifacial installation can generate more electricity than an equivalent monofacial installation, but the additional rear-side contribution should be calculated specifically for the site.
It is therefore better to look at expected annual energy yield rather than relying on a headline bifacial percentage.
The Importance of UK Location
Solar generation varies across the UK.
A system installed in southern England will generally have different solar irradiation conditions from one installed in northern England, Scotland or Northern Ireland.
However, this doesn't mean bifacial panels are unsuitable in areas with lower solar irradiation.
The panels can still generate electricity from available sunlight, including diffuse light.
The key consideration is how much useful light reaches both sides of the modules throughout the year.
Does Cloudy UK Weather Affect Bifacial Panels?
The UK's reputation for cloudy weather often raises questions about whether bifacial technology is worthwhile.
Solar panels can generate electricity during cloudy conditions because they can use diffuse sunlight, although output is generally lower than during strong direct sunshine.
Bifacial panels can also make use of light reaching their rear surface where the installation allows it.
However, the rear-side contribution will depend on the amount and direction of available light.
This means that a cloudy climate doesn't automatically rule out bifacial technology, but realistic system modelling remains important.
Surface Reflectivity
One of the biggest factors affecting bifacial energy generation is the surface underneath the panels.
A reflective surface can redirect sunlight towards the rear of the module.
Light-coloured surfaces generally reflect more light than dark surfaces, which tend to absorb more.
This makes the surrounding environment particularly important when designing a bifacial installation.
For ground-mounted systems, the ground surface can therefore have a meaningful influence on energy yield.
Panel Height
The height of the panels above the ground or roof can also affect bifacial performance.
A higher mounting position can give the rear of the panel greater access to reflected and scattered light.
It can also allow light to spread underneath the module rather than being blocked immediately by the surrounding surface.
However, higher mounting structures can increase installation costs and structural requirements.
The objective should therefore be to find a practical balance between additional energy generation and overall system cost.
Panel Spacing
Panel spacing is another important consideration.
If rows are positioned too closely together, they can reduce the amount of light reaching the rear of neighbouring modules.
Increasing the spacing can improve access to rear-side light.
However, wider spacing also requires more land or installation area.
For large UK solar farms, system designers need to balance:
Panel density + land requirements + bifacial gain + total energy yield.
The most densely packed layout isn't necessarily the one that produces the best overall return.
Tilt and Orientation
The angle and direction of the panels influence how much sunlight reaches them.
For bifacial installations, the design should also consider how sunlight interacts with the surface behind the panels.
Tilt and orientation should therefore be selected based on the location, installation type and expected solar resource.
There is no single configuration that is ideal for every UK site.
Ground-Mounted Bifacial Solar Panels
Ground-mounted systems can provide particularly favourable conditions for bifacial technology.
The panels can be elevated above the ground, allowing light to reach their rear surfaces.
The ground can also provide reflected light.
When designing a ground-mounted UK system, important considerations include:
- Ground reflectivity
- Panel height
- Row spacing
- Tilt angle
- Orientation
- Vegetation
- Shading
Optimising these factors can help increase the rear-side contribution.
Bifacial Solar Panels on Commercial Rooftops
Commercial and industrial rooftops can also be suitable for bifacial technology.
Large buildings may provide enough space for panels to be mounted with suitable clearance.
The roof surface itself can also influence rear-side generation.
A lighter, more reflective roof could potentially provide more useful reflected light than a dark surface.
However, structural capacity and wind loading must always be considered as part of the system design.
Solar Carports
Solar carports are another strong application for bifacial solar panels.
Because the panels are elevated above parking spaces, there is open space beneath the modules.
This allows light to reach the rear while the surface below can contribute reflected light.
For UK businesses, retail parks, workplaces and other sites with large car parks, bifacial solar carports can potentially increase energy generation from the available structure.
What About Residential Solar?
For standard UK homes, the additional energy generated by bifacial panels may be more limited.
This is mainly because residential panels are often installed relatively close to the roof surface.
If there is little light reaching the rear, the bifacial advantage can be reduced.
However, properties with suitable mounting systems and favourable roof conditions could still benefit.
A site-specific assessment is therefore much more useful than assuming bifacial panels will provide a fixed increase in generation.
Bifaciality Factor vs Bifacial Gain
Two terms are particularly important when comparing bifacial solar panels.
Bifaciality Factor
The bifaciality factor describes the relative electrical performance of the rear side compared with the front side under defined test conditions.
Bifacial Gain
Bifacial gain refers to the additional energy actually generated by the rear side within a particular installation.
These aren't the same thing.
A panel can have a high bifaciality factor, but its real-world bifacial gain can still be relatively low if the rear receives very little useful light.
How to Maximise Energy Generation
If you're planning a bifacial solar installation in the UK, several design considerations can help maximise output.
1. Provide Suitable Rear-Side Exposure
Don't unnecessarily block the rear of the modules.
2. Consider Surface Reflectivity
A suitable reflective surface can increase the amount of light reaching the rear.
3. Optimise Panel Height
Provide enough clearance to allow useful light to reach the underside.
4. Optimise Row Spacing
Avoid unnecessarily restricting access to rear-side light.
5. Minimise Shading
Consider shading from trees, buildings and neighbouring panels.
6. Monitor Performance
After installation, monitoring can help determine whether the system is performing as expected.
Is the Extra Energy Worth the Cost?
This is ultimately one of the most important questions.
Bifacial panels and their mounting systems can sometimes cost more than a conventional installation.
However, if the additional energy generated over the system's lifetime is significant, the extra investment could potentially be worthwhile.
The correct calculation should consider:
Total installation cost → annual energy generation → electricity savings → expected lifetime → return on investment.
This is particularly important for commercial and large-scale installations.
Final Thoughts
Bifacial solar panels UK installations can generate additional electricity by capturing sunlight from both the front and rear of the module.
The UK's climate does not prevent bifacial technology from being effective, but the actual benefit depends heavily on the installation.
Surface reflectivity, panel height, spacing, tilt, orientation and shading can all influence bifacial gain.
Ground-mounted solar farms, solar carports and suitably designed commercial installations can provide particularly favourable conditions for the technology.
For residential properties, the benefits can be more dependent on the specific roof and mounting arrangement.
Ultimately, the best way to determine how much energy bifacial panels can generate is through site-specific solar modelling, rather than relying on a universal generation figure.
In the next article in this series, we'll look at installing bifacial solar panels in the UK, including positioning, mounting systems and the best surface conditions for maximising their performance.
