Power measurement of PV modules is one of the most important inspection procedures. All manufacturing companies guarantee power only at STC conditions, taking into account the age of the modules. To determine whether the PV modules of an installation are under the warranty provided by the manufacturer, it is necessary to carry out a power measurement with the greatest possible accuracy.For this reason, all manufacturers require power measurements based on the international EN/IEC 60904 and EN/IEC 60891 standards.

It is essential, therefore, that the measuring devices used, first and foremost, are accompanied by certificates regarding the measurement tolerance,and at the same time, the tolerance is as small as possible..

Τα Accredited, fixed labs,such as Fraunhofer, PI Berlin, Kiwa, etc. perform power measurements on PV modules with a tolerance of 2-3%.

Using the Mobile PV Testcenter Kmetrics is able to perform power measurements with a tolerance of 3%.  

The factors affecting the accuracy of power measurement in PV modules are the following:

• The accuracy of the instrument measuring the voltage of the electric current
• The accuracy of the instrument measuring the intensity of the electric current
• The accuracy of the instrument measuring the electrical load according to regulatory standards
• The number of actual instrument measurements for the creation of the IV curve
• The accuracy of the instrument measuring incident radiation
• The accuracy of the instrument measuring the temperature of the PV module 
• The accuracy of the instrument measuring wind speed
• The incident radiation on the module surface must be above 800W/m2 – EN/IEC 60904-
• The temperature of the measured PV module

Therefore, in order to achieve power measurement with the required accuracy, it is necessary to employ instruments of particular specifications in order to use the certified results to formulate a replacement request under the warranty to the manufacturing company.