Tremendous efforts have been made toward large-area Cu(In,Ga)Se2-based photovoltaic module fabrication with some successful commercialisation cases using a co-evaporation system. However, comprehensive implementation of the technology has been hindered due to the technological difficulties in film uniformity for scaled-up deposition. However, the quantitative impact analysis on these topics is a matter of commercial confidentiality, and it has not been possible to provide precise accounts of the processes currently used. In this technical report, an attempt has been made to statistically identify the quantitative impact of the uniformity of Cu(In,Ga)Se2 layer on the J-V characteristics of the large-area panels (120 cm × 60 cm) fabricated from a pilot in-line evaporation system. Given the assumption that reproducibility for the other process steps is high, the results deliver important grounds for setting the control limits of the compositional uniformity for quality assurance towards a highly efficient CIGS PV manufacturing line. Display omitted •The impact of the large-area (120 cm × 60 cm) CIGS film uniformity on the J-V characteristics was statistically identified.•Cu/(In + Ga) ratio in the range of 0.88–0.92 has limited influence on the efficiency of CIGS solar panels.•The RSM analysis revealed that the impact of Cu/III becomes predominant when its non-uniformity is over 4%.•The within-panel statistics revealed that the non-uniformity of the efficiency appears to be led mainly by variability in Jsc and FF.