PVsyst Yield Simulations: What the Numbers Actually Tell You
A PVsyst report has one headline number and a dozen supporting ones. Here's how to read past the headline and understand what's actually driving a project's expected output.
Pathworks Engineering Team
The specific-yield figure on the first page of a PVsyst report gets quoted constantly and understood shallowly. It's a useful summary, but the report underneath it is where the real information about a project's expected performance actually lives.
The loss diagram is the most useful page in the report
PVsyst's loss diagram breaks down every factor between theoretical irradiance and delivered AC energy — shading, soiling, temperature, wiring resistance, inverter clipping, and more. A yield number without its loss diagram is missing the explanation for why it landed where it did.
Shading analysis quality depends entirely on input quality
Near-shading from parapets, HVAC equipment, or adjacent structures can meaningfully affect yield, and the accuracy of that analysis depends on how carefully the 3D scene was modeled. A rough shading model on a site with real obstructions can materially overstate expected yield.
Performance ratio tells you more than raw output
Two systems can report similar specific yield while having meaningfully different performance ratios, because PR normalizes for irradiance and isolates system-level losses. PR is generally the more useful number for comparing design quality across projects or design iterations.
Degradation assumptions compound over the system's life
A small difference in assumed annual degradation rate has an outsized effect on year-25 output projections used in financing models. It's worth checking what degradation assumption a report used before treating its long-term projections as fixed.
What we deliver alongside the number
Every PVsyst report we produce comes with the underlying loss diagram and shading model, not just the summary page, specifically so the design team can see what's driving the number rather than taking it on faith.
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