At first glance, the reason for higher energy generation with bi-facial panels seems obvious: when you have space beneath ground-mounted panels, reflected light from the surface below can be harvested by the underside of the panels. However, the difference in production might surprise you, as it did us. In our latest ground-mount installation and study, we’ve observed a remarkable 26% increase in energy production by switching from traditional, single-sided modules to modern bi-facial panels. Here’s what’s behind that impressive boost—and why bi-facial technology is rapidly gaining popularity for ground-mounted systems.
How Bi-facial Panels Work
Bi-facial solar modules, unlike traditional monofacial modules, are capable of collecting sunlight from both the front and the back. The front side of the panel captures direct sunlight, just like a conventional panel. The backside, however, captures light reflected off the ground or nearby surfaces, often referred to as "albedo light."
Key factors that influence the amount of extra energy the rear side can collect include:
Surface reflectivity (albedo): Lighter-colored or reflective surfaces (e.g., concrete, white roofing, or even snow) can bounce a greater portion of sunlight back up to the underside of the panels.
Panel height & tilt: Elevating the panels further above the ground and adjusting the tilt angle can increase the rear-side irradiance, which translates into higher energy yields.
Row spacing and layout: Allowing proper space between rows of panels helps reduce shading on the backside and enables more light to reach the ground.
Why Ground-Mount Installations Benefit
In a ground-mount setup, there’s typically more open space beneath the array. This extra room allows more light to scatter around and find its way to the underside of the panel. Additionally, when ground surfaces have high reflectivity—such as a gravel bed, grass with high moisture content, or specialized reflective coatings—the rear side of the modules captures significantly more photons than it would in a rooftop setup.
Even in sites with standard grass or moderate reflectivity, the effect can be substantial. In fact, real-world data from bi-facial systems in various climates suggests that even in non-ideal conditions (like cloudy regions or less reflective ground), a 5–20% rear-side gain is not uncommon. In our observed case, optimized conditions produced a striking 26% boost in total energy output compared to similar monofacial arrays.
Real-World Results
Higher Daily Output The additional sunlight captured by the backside of bi-facial panels can extend peak production time. When the sun is at a lower angle—morning or late afternoon—a portion of the solar rays that might otherwise miss the front side are reflected by the ground and caught by the rear.
Performance in Diffused Light Bi-facial modules also perform well under overcast or cloudy conditions. Because overcast skies scatter light more evenly, some of that diffuse light reaches beneath the panels, providing a noticeable bump in energy collection compared to monofacial panels on similar cloudy days.
Long-term Return on Investment While bi-facial panels can be marginally more expensive than their monofacial counterparts, the increased energy yield often makes up for that cost difference in a relatively short time. Factors like local electricity prices, available space, and installation costs all play a role, but many system owners find that the improved performance translates into a more attractive payback period.
Case Study
Take a look at these two ground mount isntallations. The first uses 500W Bauer panels (mono-facial): System: 5592858
The smaller system produces more power with two fewer panels. The kWh per kW DC measure shows that the system with bi-facial panels was 26% more efficient than the mono-facial panels in the 30 day time period from February 21st 2025 to March 21st 2025.
This difference in production was more than we expected to see and came as quite a surprise. Although bi-facial panels come at a higher cost per watt than standard mono-facial panels we highly encourage this selection for ground mounts.
Conclusion
Considering a ground mount installation? We think bi-facial panels are the way to go, and we have the data to prove it. It goes without saying that each installation has differenct characteristics so the results will certainly vary, but from what we've seen the cost difference for bi-facial panels is jsutified by the additional yield.
