November 13, 2020 | by Brittany Good | Engineering + Technology

SolarServices Revolve LIIt has been a few years since IEC 61724, the standard outlining guidelines for the measurement, data exchange, and analysis of photovoltaic (PV) systems performance monitoring, underwent a significant update. This technical revision broke IEC 61724 into three separate standards: IEC 61724-1, -2, and -3, where 61724-1 provides guidance to keep measurement errors of operating PV plants within specified limits. This is achieved by separating monitoring systems into three accuracy classes – A, B, and C – with each one being defined by the hardware used in the measurement system as well as through quality checks and performance metrics.

Specifications for the three accuracy classes are as follows:


Class A

Class B

Class C










PV plant size guidance



Utility-scale or large commercial


Small commercial or residential


Small commercial or residential


Irradiance measurements required


  • POA
  • GHI
  • DNI (for CPV)
  • Diffuse (for CPV w/ < 20x concentration) 


  • POA*
  • GHI*
  • DNI* (for CPV)
  • Diffuse (for CPV* w/ < 20x concentration) 



  • POA*


Environmental measurements required



  • PV module temperature
  • Ambient temperature
  • Wind speed
  • Wind direction
  • Soiling ratio (if losses are expected to be >2%)
  • Rainfall


  • PV module temperature*
  • Ambient temperature*
  • Wind speed*
  • Rainfall*



  • Ambient temperature*




Irradiance sensor maintenance



  • Recalibrate annually
  • Clean weekly
  • Heating required depending on conditions
  • Ventilation required


  • Recalibrate every 2 years
  • Clean optional
  • Heating required depending on conditions
  • Ventilation optional


  • Recalibrate per manufacturers’ requirements

System inspection



Not required

*Value may be estimated based on nearby meteorological or satellite data.

Thanks to our complete system approach to solar monitoring, NRG is well-positioned to provide everything you need – from hardware to software to services – to meet your needs according to IEC 61724-1. According to Michael Fisher, NRG’s Product Manager for Solar, “The solar industry is currently grappling with a low-performance bias like was experienced in the wind energy industry around ten years ago. Adoption of and adherence to standards like this are critical to increased consistency and efficiency within the industry. Systematically building that kind of quality into PV systems should ultimately translate into better results for the industry and their end customers, the ratepayers.”

NRG Systems’ portfolio of irradiance and environmental sensors satisfy the full range of Class A measurement requirements. “The EKO MS-80 and Hukseflux SR30-D1 are two exceptional pyranometers offered by NRG that boast Class A accuracy as well as heating and ventilation capabilities,” says Fisher. Both sensors also integrate seamlessly with NRG’s SymphoniePRO Data Logger for worry-free data collection and delivery. Fisher continues, “From there, add in NRG’s PVT1 PV Temperature Sensor, Soiling Measurement Kit, and our suite of field-proven meteorological sensors and your hardware requirements are met.”

Thanks to our highly-skilled team and extensive global partner network, NRG can also assist with IEC-compliant system design and configuration based on your project’s unique needs, as well as installation and maintenance, including cleaning and inspection schedules. “The advantage here,” says Fisher, “is the unparalleled ease-of-use of designing, installing, and maintaining a Class A resource measurement system through a single provider. This streamlined approach is really the most powerful way to increase overall efficiency, saving our customers time and improving their chances of staying on budget and on schedule.”

To learn more about NRG’s solar offerings, contact

Brittany Good

As NRG’s Senior Marketing Specialist, Brittanywho has a background in journalism and digital marketingis responsible for making sure that the company’s voice is heard across all communication channels, including the website, email campaigns, videos, press releases, and print collateral. She enjoys the challenge of crafting intriguing content that strengthens NRG’s relationships with its customers while engaging new audiences.      

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