Measure output quality using energy and sunlight inputs. Add practical losses for realistic expectations. Export clean reports for audits and handovers today.
Performance Ratio (PR) compares actual energy to the energy implied by available sunlight:
The modeled PR multiplies availability and loss factors: PRmodeled = A · ∏(1 − loss). Modeled expected energy is Emodeled = P0 · Yr · PRmodeled.
| Scenario | Capacity (kWp) | Energy (kWh) | POA Irradiation (kWh/m²) | Measured PR | Notes |
|---|---|---|---|---|---|
| Commissioning week | 120 | 15,500 | 83 | 78.0% | Stable sensors, minor cleaning needed. |
| Dusty month | 250 | 29,500 | 165 | 72.0% | Soiling and shading from temporary works. |
| Optimized operations | 500 | 70,500 | 180 | 78.0% | Good availability and timely washing. |
| Curtailment period | 400 | 52,000 | 175 | 66.0% | Export limited during peak hours. |
| Post-maintenance | 300 | 40,500 | 150 | 90.0% | Meter verified, wiring losses corrected. |
These examples demonstrate typical ranges seen during construction and early operation.
Performance Ratio (PR) is a normalized quality indicator used during commissioning and handover. It removes most weather variability by relating delivered AC energy to plane-of-array irradiation and installed capacity. For new builds, a stable PR trend is often more useful than a single high reading.
Typical early-operation targets are 0.70–0.85 for fixed-tilt systems, depending on climate and cleanliness. Tracking systems may show different seasonal patterns, so compare like-for-like periods.
Use a verified AC export meter and a calibrated irradiation sensor. A small sensor bias can move PR by several points. Keep timestamps aligned: energy and irradiation must cover the same window. Note inverter outages and maintenance actions.
Recommended practice: log sensor checks weekly during construction, and after any wiring or sensor relocation. Record cleaning dates, because soiling effects can appear as a gradual PR slide.
The modeled PR in this tool multiplies availability and a loss stack to create an expected baseline. Common allowances include temperature (4–10%), soiling (1–6%), inverter losses (2–4%), and wiring (1–3% combined). Use site history to replace defaults with measured values.
If measured PR is close to modeled PR, the system is behaving as expected for the assumptions. If it is lower, prioritize the largest and most uncertain loss categories first.
A commissioning checklist can pair PR with quick validations: string currents, inverter efficiency, and sensor plausibility. For example, sudden PR drops often correlate with tripped breakers, incorrect CT direction, or shading from temporary cranes.
Use the “uncurtailed PR” estimate when export limits apply. It helps separate grid constraints from equipment performance. Always document the curtailment method used, because assumptions vary by project.
The table below shows a compact dataset format suitable for daily logs. It supports quick PR trending and loss attribution.
| Date | Energy (kWh) | POA (kWh/m²) | Availability (%) | Curtailment (%) | Measured PR |
|---|---|---|---|---|---|
| 2026-01-05 | 1,020 | 5.40 | 99.2 | 0.0 | 79.0% |
| 2026-01-06 | 980 | 5.20 | 97.8 | 2.5 | 76.5% |
| 2026-01-07 | 1,070 | 5.55 | 99.6 | 0.0 | 80.1% |
| 2026-01-08 | 910 | 5.45 | 95.1 | 0.0 | 69.6% |
Example assumes 250 kWp capacity and standard reference irradiance. Adjust fields to match your QA template and meter configuration.
It is the ratio of delivered energy yield to reference yield from sunlight. PR normalizes weather effects, letting you compare system quality across periods and sites.
Use plane-of-array irradiation integrated over the same period as the energy meter. Prefer calibrated sensors mounted in the array plane, with clear maintenance and cleaning records.
Modeled PR sets a realistic expectation using availability and losses. The gap highlights whether shortfalls come from assumptions, site conditions, or equipment issues.
Enter a curtailment percentage when export is limited. The tool also estimates an uncurtailed PR to separate grid constraints from true system performance.
Temperature 4–10%, soiling 1–6%, inverter 2–4%, wiring 1–3%, shading 0–5%. Temporary works and incomplete cleaning often increase soiling and shading losses.
Confirm meter mapping and CT direction, then verify irradiation sensor calibration and time alignment. Review inverter alarms, availability logs, and any recent shading from cranes, scaffolds, or parapets.
During commissioning, daily or weekly reporting helps catch wiring and configuration issues quickly. After handover, monthly reporting is common for performance assurance and warranty documentation.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.