Thanks Richard for your excellent analysis. I am a retired engineer myself and have been monitoring my system for 7 years. I have a 4.23kW system with 18 x 235W REC panels and SMA inverter. The panels are installed on a shallow angled garage roof with 16 panels facing West and 8 panels facing East. Surprisingly, my actual annual output is significantly higher tham the expected annual output.I have difficulties finding a chart with the theoretical/actual solar irradiation figures (annually, month ...