The authors have developed a monitoring service of monthly generation for small-scale solar power plants and proposed “Simplified System Performance Ratio (sPR)” that can grab degradation of annual generation of PV using simple generation monitoring system and data from neighbouring weather station. This report introduces the result of investigation of totally 272 power plants in Japan and relationship between various parameters and sPR’s degradation using regression analyses. The result clarifies that there is a statistically significant correlation between sPR and FIT buying price as well as the presence or absence of a low-voltage division.
