Loss waterfall
The waterfall is the equivalent of the «loss diagram» in simulation reports: it starts from the horizontal irradiation and arrives at the net energy delivered by the inverter, showing each loss (in red) or gain (in green) as a percentage of the previous level.
It is calculated with the hourly data of all the strings, not just one, so the levels chain together exactly.
Rows of the waterfall
Irradiation (kWh/m²)
| Row | What it shows |
|---|---|
| Global horizontal irradiation | Starting point: the solar resource of the typical year |
| Transposition to the module plane | Gain or loss from tilting and orienting the modules |
| Global incident irradiation on the plane | Level |
| Shading (rows, horizon, obstacles) | If there is shading |
| Angle of incidence (IAM) | Reflection on the glass |
| Soiling | If the level is not «Clean» |
| Effective irradiation on the plane | Level: what reaches the cells |
Energy (kWh)
| Row | What it shows |
|---|---|
| Nominal array energy (STC) | Level: what it would give with the catalogue efficiency |
| Irradiance level (low light) | Efficiency loss in low light |
| Cell temperature | Loss (or gain) due to temperature |
| Spectral effect | Spectral adjustment |
| Module mismatch | Aggregated loss |
| DC cabling (ohmic losses) | Aggregated loss or calculated with real cross-sections |
| Connections | Aggregated loss |
| System availability | Aggregated loss |
| Mismatch between parallel strings (shading) | Only if applicable |
| Virtual array energy at MPP | Level: what the inverter receives |
| Inverter: power threshold (does not start) | If there is a measured curve |
| Inverter: conversion efficiency | DC → AC |
| Inverter: clipping at nominal power | Clipping |
| Energy available at the inverter output | Level |
| Inverter: night-time consumption (stand-by) | Own consumption |
| Net energy delivered (AC) | Final result |
Order of the losses
The «irradiance, then temperature» order is the PVsyst one. The engine applies both factors by multiplying hour by hour, so the breakdown is exact with that order.
Performance Ratio (PR)
PR = Net energy delivered (AC) / ( Incident irradiation on the plane × Peak power )
This is the PVsyst definition. A typical PR for a well-designed residential self-consumption system is around 80-85 % (it depends on temperature, shading and clipping).
How to use it
- If a loss is surprising (shading, cabling), act on it and simulate again.
- Compare the waterfall of two scenarios to see where energy is gained or lost.
- In the report it appears as Annex C.
Press the «?» on each row to see its short explanation.