Performance Ratio (PR) Calculator

Measure the real efficiency of your solar plant. Enter production, installed capacity and irradiation to obtain the key quality indicator (KPI).

What is Performance Ratio (PR)?

Performance Ratio (PR) is the most important indicator for evaluating the quality of a photovoltaic installation, regardless of location or size. It represents the percentage of theoretical energy (available as sunlight) that is actually converted into useful electricity exported to the grid.

A PR of 100% is physically impossible due to thermodynamic laws and inevitable electrical losses. The goal is to get as close as possible to the technical limit.

The PR Formula

// Simplified calculation

PR (%) = (Real Energy / Theoretical Energy) × 100

// Theoretical Energy (Reference Yield)

Theoretical Energy = In-Plane Irradiation (H_i) × Installed Power (P_0)

Typical Reference Values

< 75%

Low

Indicates serious problems: shading, extreme soiling, inverter failures or accelerated degradation.

75% - 80%

Acceptable

Common in old plants (10+ years) or in very hot climates where thermal losses are high.

80% - 90%

Excellent

Current standard for new Utility Scale plants that are very well optimized and maintained.

Main Losses

Temperature: Panels lose efficiency with heat (~ -0.35%/°C).
Wiring (DC/AC): Ohmic losses from energy transport.
Inverter: DC/AC conversion efficiency (typically 98-99%).
Soiling: Dust, pollen or bird droppings.
Shading: Distant horizon, nearby obstacles or between rows.

Managing a plant portfolio?

Automate PR calculation. Connect your plants to the PV Maps Dashboard to monitor daily performance, detect losses and compare with market benchmarking.

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