Performance variability and implications for yield prediction of rooftop PV systems – Analysis of 246 identical systems

•246 identical rooftop PV systems in 19 residential communities are analyzed.•Mechanisms of PV performance variability are investigated by controlled comparison.•PV performance variability increases in the field compared with STC.•Shading and masking effects play a prominent role even in low-rise suburban areas.•Commissioning of in-use systems can significantly reduce PV yield prediction error.