Balancing a Multi-Building Commercial Solar Portfolio on Shared Inverters: A Verified 101.92 kWp Case Study
July 17, 2026
The Engineering Challenge
Not every commercial solar project is a single, uniform rooftop. In this project located in the canton of Aargau, Switzerland, the design task involved four separate buildings, ten distinct module planes, and two opposing orientations, southeast at 128 degrees and northwest at 308 degrees, all needing to be consolidated into a coherent electrical design feeding four inverters. The system totals 101.92 kWp across 208 modules, spread across roof areas ranging from just 18 square meters to over 80 square meters per plane.
The technical challenge here is not shading on one roof. It is portfolio-level electrical balancing: matching module strings of varying sizes, nine modules on some planes, forty on others, to inverters sized for the aggregate output of multiple buildings, while keeping string voltages within operating range and dimensioning factors within manufacturer tolerance across radically different array geometries.
Our Approach and Methodology
In our projects we consistently see that multi-building commercial portfolios expose the limits of simplified layout tools faster than any single complex roof. We modeled this system in PV*SOL using full 3D geometry for all four buildings simultaneously, capturing horizon shading, inter-building shading, and orientation-specific irradiance profiles for both the southeast and northwest module planes independently.
Each of the ten module areas was assigned to one of four inverter circuits based on physical proximity and string compatibility. The two smallest roof areas, at Alberich Zwyssigstrasse 53, southeast and northwest, totaling 36 modules, were combined onto a single 25 kW inverter with a dimensioning factor of 105.8 percent. The largest roof, at Zentralstrasse 93 to 99, with 80 modules split southwest and northeast, was matched to a 40 kW inverter at 98 percent dimensioning. A separate 101-Strasse rooftop with 36 modules feeding a 15 kW inverter was deliberately oversized to 117.6 percent, a decision justified by the opposing southeast and northwest split naturally limiting simultaneous peak output from both faces.
This is precisely the kind of trade-off that PV*SOL design and solar simulation work is built for: testing inverter dimensioning factors against real irradiance profiles rather than nameplate capacity assumptions, and validating that an oversized inverter on a split-orientation array will not clip meaningful energy in practice.
Why Lion Solar is Better Than Reonic and Solarmonkey for Complex Multi-Building Projects
Quick-proposal tools built for single-roof residential and small commercial quotes are not designed to handle four buildings, ten orientations, and four inverters as one integrated electrical system. Tools like Reonic or Solarmonkey are optimized for fast 2D layouts and standardized string sizing on a single roof plane, typically without full 3D inter-building shading simulation or per-plane hourly irradiance modeling across dissimilar orientations.
On a portfolio project like this one, that gap matters. Without full 3D simulation of how each building shades its neighbors at different times of day and year, dimensioning factor decisions become guesswork rather than engineering. Without hourly irradiance data segmented by module plane, an oversized inverter serving two opposing orientations cannot be confidently validated against real clipping risk. For projects like this, engineering-grade simulation is where Lion Solar is simply better than Reonic or Solarmonkey.
The Results, With Verified Numbers
The completed simulation confirms a specific annual yield of 1,027.15 kWh per kWp, with a performance ratio of 80.50 percent. Shading losses across the full portfolio were held to 5.7 percent, a strong figure given the presence of four separate buildings within line of sight of one another. Total grid feed-in is projected at 104,782 kWh per year, with avoided CO2 emissions of 39,781 kg per year.
The detailed energy balance shows the loss cascade clearly: orientation and tilt losses of 1.14 percent, reflection losses of 6.16 percent, and module-specific partial shading of 3.05 percent, all captured through full geometric modeling rather than estimated derates. The STC conversion step, unavoidable at 75.53 percent, remains the dominant factor, confirming that once module-level physics are fixed, the remaining controllable losses in a multi-building layout are precisely where careful electrical design and inverter matching pay off.
What This Means for EPCs and Investors
For EPC contractors bidding on multi-building commercial portfolios, this case demonstrates that inverter dimensioning decisions cannot be made on a per-roof basis in isolation. A 117.6 percent dimensioning factor that would be reckless on a single south-facing roof becomes a sound engineering decision when the array is split across opposing orientations that rarely peak simultaneously.
For investors and asset owners, the takeaway is that portfolio-style commercial solar, spanning multiple rooftops under one ownership structure, requires simulation methodology that treats the whole property as one interconnected system, not four separate quotes stitched together. We modeled this project end to end specifically to validate that every inverter dimensioning choice held up under full hourly simulation, not simplified assumptions. That is the standard independent engineering brings to complex, multi-asset solar portfolios before construction begins.
