Performance ratio (PR) chart

Last modified: 23 May 2025

Chart

Basic info

Description

The performance ratio is calculated based on the system yield, installed DC power, and irradiation at the module plane. It indicates how well the PV system can convert solar energy. Typically, an annual PR value of 75-85% is considered good.

Prerequisites

Energy sum at system level defined as the term E_Z_EVU
Irradiance data from a sensor defined as the term G_M0 or satellite data

Further details

Standard formula and calculation

By default, the formula from IEC 61724-1 is used in VCOM.
Standard PR formula in VCOM

Note

If you wish to define the input parameters for the PR calculation differently, see KPI editor for PR and system availability.

The smallest period of the performance ratio calculation is one day.
Monthly and annual values are aggregated accordingly and are weighted based on the projected energy.

PR chart thresholds

Define the thresholds for different performance levels (displayed as green, yellow, and red) that are reflected in the Performance ratio chart and the Performance ratio comparison chart:

Portfolio-wide for every system: On PORTFOLIO-LEVEL, under Administration > Customization > Design > Chart thresholds.
System-specific for each system separately: On SYSTEM-LEVEL, under System configuration > Calculations > Performance Ratio > PR chart thresholds.

Caution

If your site has multiple power plant controllers (blue’Log XC data loggers or third-party PPCs), each controller should be configured as a separate system, not as a subsystem. Otherwise, the performance ratio will not be calculated.

Example: A site has PV production across three rooftops, each with its own PPC. In this case, configure each rooftop in VCOM as a separate system.

To view the overall PR for the entire site, you can combine these individual systems into a virtual system in VCOM.

If you require further assistance, contact Support.