About the PR vs CUF Benchmarking
PR vs CUF benchmarking compares a solar plant's measured Performance Ratio (PR) and Capacity Utilization Factor (CUF) against the expected values for its location, technology, and age — identifying whether underperformance is due to a site resource shortfall, a system efficiency problem, or both.
How to calculate it
- 1Calculate the plant's measured PR: net AC energy ÷ (in-plane irradiation × nameplate capacity).
- 2Calculate measured CUF: net AC energy ÷ (nameplate capacity × 8760 hours).
- 3Look up location benchmarks: expected CUF from NREL/NIWE irradiance maps × a PR of 80%.
- 4Compare measured PR to the benchmark PR for the same technology (fixed-tilt monocrystalline: 78–82%; tracker: 80–84%).
- 5If PR is below benchmark: investigate site-specific losses (soiling, shading, inverter trips).
- 6If CUF is below benchmark but PR is normal: the site has less irradiance than planned — a resource/design issue.
Worked example
A 5 MW plant in Gujarat with a measured annual CUF of 16.2% and PR of 74%. Expected CUF at 5.8 kWh/m²/day: ~21%; expected PR: 80%. CUF shortfall of 4.8% is partly explained by soiling (PR only 74% vs 80% benchmark) — recovering PR to 80% alone would add ~4.4 L kWh/year at ₹3.5/kWh = ₹15.5 L/year in missed revenue.
What you can calculate
- PR rating (IEC 61724)
- State CUF benchmark
- Revenue gap ₹/yr
- 18 Indian states
Key definitions
Definitions from the SolarPedia glossary
Frequently asked questions
What is the difference between PR and CUF for benchmarking?
PR (Performance Ratio) measures how efficiently the plant converts its available solar resource into AC energy — it is system-quality focused and relatively location-independent. CUF (Capacity Utilization Factor) measures how much energy the plant produces relative to its theoretical maximum if it ran at full power 24/7 — it blends resource quality and system efficiency. Use PR to benchmark system health; use CUF to benchmark project revenue.
How often should PR be benchmarked?
Monthly PR monitoring is the minimum for grid-connected plants. A drop of more than 2 percentage points month-over-month (adjusted for seasonal irradiance variation) is a red flag warranting inspection. Many O&M contracts include a guaranteed minimum PR (typically 75–78%) with performance liquidated damages.
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