Why PR Is the Most Disputed Number in Solar
Performance Ratio is supposed to be the universal yardstick of plant health. In practice, two engineers staring at the same plant routinely disagree by 2–4 percentage points — because they normalised data differently, used different irradiance sources, or took different averages.
Where PR Breaks Down
- Raw telemetry: 1-second inverter data has gaps, spikes and clock drift. Computing PR straight from raw streams produces wildly different numbers depending on the gap-filling rule.
- Irradiance source: Pyranometer vs reference cell vs satellite — different POA assumptions move PR by ±2%.
- Temperature correction: Module datasheet temperature coefficients vary; some operators skip the correction entirely.
- Boundary conditions: Including or excluding low-light periods (early morning, sunset) shifts daily PR meaningfully.
How Enlyra Pins It Down
Enlyra computes PR deterministically on the analytical layer (PostgreSQL), never on raw telemetry. Inputs come from the 1-min and 15-min normalised aggregates with explicit gap-filling rules. POA irradiance is reconciled across pyranometer, reference cell and weather station with documented precedence. Temperature correction uses the module datasheet coefficients stored in plant configuration — not assumed defaults.
Reproducibility, Always
Every PR figure in Enlyra is reproducible from the underlying datasets. Every IEC report ships with the calculation trace. EPC audit teams can re-derive the number themselves — and consistently do.