## 4 Conclusions  
This study analyzes the performance and reliability parameters of a long-term grid-connected PV system operation that was exposed to moderately continental climatic conditions in Nis (Serbia). Based on the experimental results, this study shows that:  
* The yearly average values of POA radiation on a south-oriented and optimally inclined plane and total POA radiation on the PV array for a 10-year measurements level are 120.5931 kWh/m\({}^{2}\) and 1,999,512 kWh, respectively. * The total electricity production of the PV system for 10 years of its operations is 22,934.65 kWh. * The yearly average value of PV system efficiency, for the 10-year measurements level, is 10.49%, which is almost two times less than the given efficiency at STC, and the relative error of yearly average values of PV system efficiency, observed from year to year, range from 0.34% to 6.16%. * The yearly average value of specific yield factor (Y\({}_{\text{f}}\)) for the 10-year measurements level is 1178.51 kWh/kW\({}_{\text{P}}\). * The yearly average value of CF over the 10-year period is 13.45%. * The yearly average value of PR for the 10-year measurements level is 0.87, and the relative error of yearly average values of PR, observed from year to year, range from 0.97% to 6.83%. On the other hand, the PV system, which uses highly efficient components and is designed appropriately, shows a PR near 90% (\"good\" performances are >84%). Thus, the experimental results indicate that the behavior of the given PV system over 10 years of operation does not change significantly. Based on a statistical analysis of PV system electricity and total POA radiation on PV array data over 10 years of measurements, it can be concluded that:  
* A high correlation coefficient value allows for the formation of regression model between PV electricity and POA radiation of the PV array. The obtained model is statistically significant and enables prediction better than the simple average. * ANOVA shows that the mean values of PV electricity are not statistically significant changed over the 10 observed years. * ANOVA and post hoc Tukey test show that there is a statistically significant difference of POA mean radiation during the months over 10 years and that the highest values of POA radiation are in July and on August. The Tukey test enables the months to be separated within the groups based on difference of POA radiation on PV array. The months within the groups are without statistically significant differences of POA radiation, while the months in various groups differ statistically significantly in terms of POA radiation. * Based on the POA radiation values and by applying the obtained model, a prediction of the PV system output can be made for similar PV installations. It should be also noted that, by making the presented results publicly available, this research could benefit researchers in increasing the accuracy of modeling, prediction, and the cost-effectiveness of PV systems over a longer period of their operation. **Author Contributions:** [PERSON] and [PERSON] wrote the manuscript. [PERSON] and [PERSON] performed conceptualization. [PERSON] and [PERSON] performed final analysis. [PERSON] and [PERSON] applied software. [PERSON] and [PERSON] provided validation of the results. [PERSON] and [PERSON] provided the methodology and conducted research [PERSON] and [PERSON] reviewed the manuscript. All authors have read and agreed to the published version of the manuscript. **Funding:** Ministry of Education, Science and Technological Development of the Republic of Serbia for support under Contract No. 451-03-47/2023-01/200123. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.