How yield is computed
How SolarLayout estimates electricity production over your plant's lifetime.
SolarLayout estimates electricity production over the plant lifetime, which defaults to 25 years and is configurable (1–50 years) under Performance & Lifetime on the Energy modeling tab. The estimate uses hourly weather data, your module and inverter specs, and an industry-standard losses model.
What goes in
Weather data
PVGIS satellite data by default, or upload your own hourly CSV (Solargis, Meteonorm, etc.)
Module spec
A PAN file you upload to your Resource Library — SolarLayout doesn't ship a preloaded module catalog
Inverter spec
An OND file with efficiency curves, uploaded to your Resource Library — no inverters come preloaded
Site environment
Albedo, soiling rate, tilt, mounting type
PAN and OND are the industry-standard file formats for solar modules and inverters. Most manufacturers publish them — you'll usually find them on the vendor's downloads page alongside the datasheet.
Exceedance probabilities — three numbers, one report
An exceedance probability (a "P-value") is the probability that actual production meets or beats a given figure. P50 is the median — half of years will exceed it; P90 is conservative — 90% of years will exceed it. Lower-exceedance figures matter to base-case engineering and feasibility; higher-exceedance figures matter to lenders, because debt service has to be paid in bad years too.
SolarLayout reports three of these figures. By default they are P50, P75, and P90, but you can change any of them to match your project or what your lender asks for. Under Probabilistic Analysis on the Energy modeling tab you set the three percentages yourself (anywhere from 1 to 99), along with an overall uncertainty figure that controls how far apart they fall. The on-screen energy summary and the PDF report then use exactly the figures you picked — for example, change the middle one from 75 to 80 and you'll see a P80 value in its place.
The spread between the figures reflects inter-annual irradiance variability and the combined uncertainty you set. A typical utility-scale project sees P90 land roughly 5–8% below P50.
The losses model
Production losses compound multiplicatively into a single Performance Ratio. Typical values:
| Loss type | Typical range |
|---|---|
| Soiling | 2–4% (higher in arid / dusty regions; cleaning schedule matters) |
| Temperature | 5–10% (depends on summer ambient and module tech) |
| Mismatch | 1–2% |
| DC wiring | 1–2% |
| AC wiring | 0.5–1% |
| Transformer | 0.5–1% |
| Shading | 0–1% on well-sited plants |
| Inverter | per the OND efficiency curve |
| Availability | 99%+ |
Total system-level losses typically land in the 12–18% range.
See Losses & soiling for the model details and how to tune the soiling assumption for your specific site.
Bifacial modules
If your module is bifacial (the back side also generates electricity), SolarLayout adds a rear-side production contribution. See Bifacial modules for the model inputs (bifaciality factor, ground albedo) and how to configure them.
Custom weather data
PVGIS satellite data is fine for early-stage feasibility and quick screening. For bankable submissions, lenders typically require Solargis or Meteonorm data, or 12+ months of on-site pyranometer measurements.
See PVGIS vs custom CSV for how to attach your own hourly weather file to a project.