What are the IEC 61724-1 monitoring classes for solar sites?
IEC 61724-1:2021 defines two PV monitoring accuracy classes: Class A (high accuracy, for utility-scale and large commercial plants) and Class B (medium accuracy, for rooftop and smaller systems). The former 2017 Class C is now Class B. Class A requires pyranometer dew and frost mitigation unless dew or frost is rare.
The short version
| Class A | Class B | |
|---|---|---|
| Accuracy | High | Medium |
| Typical use | Utility-scale and large commercial plants | Rooftop and small to medium commercial systems |
| Irradiance sensor dew and frost mitigation | Required, except where dew or frost affects under about 2% of annual GHI hours | Not stated in the summary we reviewed |
Under the 2017 edition there were three classes (A, B, C). In the 2021 edition the old Class C became Class B.
What the standard covers
Per the manufacturer summary, the standard sets accuracy requirements for measurements such as module and air temperature, wind speed and direction, soiling ratio, current and voltage, and tilt and azimuth, and defines cleaning and calibration intervals for pyranometers. We have not confirmed the specific values; check the standard.
Why it matters when buying
Lenders, owners and performance contracts often reference the class. Confirm which class your contract or financing requires before choosing sensors, because the class drives sensor grade, maintenance and calibration.
Questions to ask providers
- Which edition and class of IEC 61724-1 does this package conform to, and is there documentation?
- Which irradiance sensor class is included, and how is dew and frost handled?
- What calibration and cleaning intervals do you specify?
- Are soiling measurements included?
Sources
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