Quantifying Rooftop Shading Losses on a 50 kWp Commercial Solar Array Through 3D Simulation
July 17, 2026
The Engineering Challenge: A High-Yield Roof With a Hidden Shading Problem
A 50.47 kWp rooftop solar installation on a commercial building in the Winterthur region presented a design puzzle that is common but frequently underestimated. The roof face was south facing at 183 degrees azimuth with a 26 degree tilt, a textbook orientation that should deliver near-optimal yield with minimal losses. Yet our PV*SOL based simulation identified an 11.7 percent yield reduction from shading alone, a figure far above what a generic irradiance calculator or a quick 2D proposal tool would predict for this orientation and tilt combination.
The system comprises 103 LONGI Solar LR7-54HVH-490M modules feeding a single Huawei SUN2000-50KTL-M3 inverter at a 102 percent DC to AC sizing ratio. On paper, this is a clean single string design. In practice, surrounding trees, adjacent structures and the roof geometry itself created horizon obstructions and near shading effects that only became visible once we modeled the full 3D environment rather than relying on a flat horizon assumption.
Our Approach: Full 3D Horizon and Near-Shading Modeling
In our projects we consistently see that orientation and tilt figures alone tell only part of the story. For this Winterthur rooftop, we modeled the complete horizon line using 3D terrain and object data, capturing the actual skyline as seen from every module row rather than a simplified sun path diagram. We then layered near shading analysis on top, accounting for parapets, mechanical equipment and vegetation immediately adjacent to the array.
This is part of our PV*SOL design and PV planning service for EPCs and developers, where we simulate hourly generation across a full year using DWD TMY3 climate data at one hour resolution. The horizon plot generated for this site showed obstruction angles reaching into the 15 to 20 degree range during winter months, when low sun angles are most sensitive to nearby structures. This detail explains why the specific yield still reached 1215.21 kWh/kWp for the year even with an 11.7 percent shading penalty, since the loss is concentrated in specific months and hours rather than spread evenly.
Why Lion Solar is better than Reonic and Solarmonkey for shading-sensitive rooftop projects
Quick-proposal platforms such as Reonic or Solarmonkey are built for speed, generating a sales-ready layout and yield estimate in minutes based on simplified obstruction inputs or none at all. For a flat, unobstructed roof this can be adequate. For a site like this Winterthur rooftop, where the eventual measured shading loss reached nearly 12 percent, a tool that does not model the full 3D horizon and near shading geometry will systematically overstate expected production.
The practical difference lies in the inputs each approach can actually process. Standard 2D or quick-proposal workflows typically rely on manual entry of a single tilt and azimuth value with no per-hour horizon profile, and they do not generate the kind of shading-versus-time breakdown that explains where and when losses occur. Full 3D simulation in PV*SOL builds the horizon line object by object and calculates shading losses on an hourly basis across the entire climate year, which is the only way to catch a result like the 11.7 percent figure here before construction rather than after. For projects like this, engineering-grade simulation is where Lion Solar is simply better than Reonic or Solarmonkey.
Results: Verified Numbers From the Simulation
The completed simulation produced the following verified results for the 50.47 kWp array:
- Specific annual yield: 1215.21 kWh/kWp
- Performance ratio (PR): 82.59 percent
- Yield reduction from shading: 11.7 percent
- Grid feed-in: 61,357 kWh per year
- First-year grid feed-in including module degradation: 61,012 kWh
- Avoided CO2 emissions: 28,826 kg per year
- Inverter standby consumption: 25 kWh per year
The monthly generation profile confirms the shading impact directly. January output was only 1,610 kWh against a July peak of 7,430 kWh, a spread that reflects both seasonal irradiance and the fact that low winter sun angles interact more strongly with the horizon obstructions identified in our 3D model. The energy balance breakdown further shows that orientation and tilt actually contributed a positive 19.00 percent gain relative to horizontal irradiance, meaning the shading loss is a distinct, separately quantified factor rather than being absorbed into a generic derating assumption.
What This Means for EPCs and Investors
For EPC contractors bidding on rooftop projects with any degree of surrounding obstruction, whether from adjacent buildings, trees, or rooftop equipment, this case demonstrates why a full 3D shading simulation should be a mandatory step before finalizing module count and inverter sizing. A design based on orientation and tilt alone would have projected a materially higher yield than what the site can actually deliver, creating a gap between contract expectations and delivered performance.
For investors and asset owners, the 11.7 percent shading figure is exactly the kind of variable that belongs in a bankable yield assessment. We modeled this system using the same rigor we apply across our PV*SOL design and simulation services, treating shading not as a rounding error but as a quantified, hourly-resolved loss category with its own line item in the energy balance. That level of detail is what separates a defensible production forecast from an optimistic sales estimate, and it is the standard we apply to every rooftop and ground-mount project we simulate for EPCs and developers.
