PR — Performance Ratio
Technical
Performance Ratio, or PR, is the ratio between the actual electricity produced by a solar PV (PLTS) system and the theoretical energy it should produce at STC conditions with the same irradiance. PR is a system-quality indicator commonly used by EPCs and IPP developers to monitor PLTS performance over its operating life.
PR is calculated with a simple formula: the actual measured energy (kWh) divided by the product of installed capacity (kWp), total period irradiation (kWh/m²), and the 1 kWp/m² reference. The result is a dimensionless figure, usually between 0 and 1, that summarizes all system losses: temperature derating, soiling, inter-module mismatch, DC and AC cable losses, inverter efficiency, and downtime.
For tropical PLTS systems in Indonesia, a typical PR is in the 0.75-0.82 range [IEA PVPS Task 13]. New on-grid systems with professional installation and routine cleaning generally reach a PR of 0.80, while older systems, those exposed to high soiling, or those in industrial environments with hotter module temperatures tend to fall to 0.75.
PR differs from capacity factor: PR measures the quality of the system's conversion relative to the available solar resource, whereas capacity factor measures actual production relative to installed capacity running 24/7. PR is the more relevant metric for evaluating a PLTS system's technical health.
Indonesian PLTS Application Example
A 100 kWp rooftop PLTS in Bandung (PSH ~4.8 kWh/m²/day [NASA POWER 1984-2023]) with a PR of 0.80 yields an estimate of 100 × 4.8 × 0.80 × 365 ≈ 140,160 kWh per year. If annual monitoring shows an actual output of 125,000 kWh, the actual PR falls to 0.71 — a signal to investigate soiling, increased shading, or declining inverter performance.
Sources & References
- Performance, Operation and Reliability of Photovoltaic Systems — IEA PVPS Task 13 (latest)
- SolarPlanner.id Calculator Data, SECTION 3 (default PR 0.80 for Indonesia) — SolarPlanner.id (2025)
- SolarPlanner.id calculator methodology (placeholder — activation after LUMEN methodology sprint) — SolarPlanner.id (2026)
See Also
Derating Factor
The derating factor is a reduction factor that makes a solar PV (PLTS) system's actual output lower than its nominal STC capacity. Derating covers cell-temperature losses, surface soiling, module mismatch, DC and AC cabling, and inverter efficiency. For Indonesia's tropical climate, the combined derating is usually in the 80-85% range.
PSH
(Peak Sun Hours)PSH, or Peak Sun Hours, is the number of equivalent sunlight hours during which an average irradiance of 1,000 W/m² is received on a horizontal surface per day. Its unit is kWh/m²/day. PSH is the core variable determining how many kWh per day each kWp of solar panel produces at a given location.
BOO
(Build-Own-Operate)BOO, or Build-Own-Operate, is a solar PV (PLTS) financing scheme in which a developer builds, owns, and operates the installation on land or rooftop belonging to the tenant, while the tenant pays for electricity per kWh over the contract term — typically 10-25 years. There is no upfront capital outlay on the tenant's side.
MPPT
(Maximum Power Point Tracking)MPPT, or Maximum Power Point Tracking, is an electronic algorithm inside a solar inverter or charge controller that continuously tracks the maximum power point of the panel's voltage-current curve so that DC-to-AC conversion occurs at the highest efficiency. Mainstream inverters in the Indonesian market generally have an MPPT efficiency of 96-99% — a ~3% spread that directly affects the system's realized Performance Ratio.