PR/Performance ratio chart

Last modified: 2026-07-29

Chart

View the chart at System level in the Evaluation tab in the Section: System KPIs.

Basic info

Description	The performance ratio is calculated based on the actual generated energy (= system yield), installed DC power, and POAI/Plane-of-array irradiance. It indicates how well the PV system can convert solar energy. Typically, an annual PR value of 75-85% is considered good. In the chart, the bars represent the system’s normalized actual energy (PV Yield), and the dots represent the PR/Performance ratio. The color of the dots corresponds to the threshold specified for the rating of the PR.
Prerequisites	Actual energy term `E_Z_EVU` is defined. See Terms. Plane of array irradiance/POAI term `G_M0` is defined. See Terms.
Further details	Calculation The smallest period of the PR calculation is one day. Editable calculation parameters With the VCOM module KPI Editor, you can: Adapt the calculation parameters to your needs. See KPI Editor and KPI Editor: Performance ratio (PR). Edit the thresholds that rate the PR. See PR chart thresholds. Without the KPI editor, the default PR formula from IEC is used. Default PR formula Default IEC PR formula

Description

The performance ratio is calculated based on the actual generated energy (= system yield), installed DC power, and POAI/Plane-of-array irradiance. It indicates how well the PV system can convert solar energy. Typically, an annual PR value of 75-85% is considered good.

In the chart, the bars represent the system’s normalized actual energy (PV Yield), and the dots represent the PR/Performance ratio. The color of the dots corresponds to the threshold specified for the rating of the PR.

Prerequisites

Actual energy term E_Z_EVU is defined. See Terms.

Plane of array irradiance/POAI term G_M0 is defined. See Terms.

Further details

Calculation

The smallest period of the PR calculation is one day.

Editable calculation parameters

With the VCOM module KPI Editor, you can:
- Adapt the calculation parameters to your needs. See KPI Editor and KPI Editor: Performance ratio (PR).
- Edit the thresholds that rate the PR. See PR chart thresholds.
Without the KPI editor, the default PR formula from IEC is used.

Default PR formula

Basic PR formula IEC.png — Default IEC PR formula

Caution

If your site has multiple power plant controllers (blue’Log XC data loggers or third-party PPCs) and you want to monitor each individually, 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.

Note

Find further information on the general functions within charts under Evaluations & charts.