IEC 61724-1:2021 is available as IEC 61724-1:2021 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.

IEC 61724-1:2021 outlines terminology, equipment, and methods for performance monitoring and analysis of photovoltaic (PV) systems. It also serves as a basis for other standards which rely upon the data collected. This document defines classes of photovoltaic (PV) performance monitoring systems and serves as guidance for monitoring system choices. This second edition cancels and replaces the first edition, published in 2017. This edition includes the following significant technical changes with respect to the previous edition:
- Monitoring of bifacial systems is introduced.
- Irradiance sensor requirements are updated.
- Soiling measurement is updated based on new technology.
- Class C monitoring systems are eliminated.
- Various requirements, recommendations and explanatory notes are updated.