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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, monthly, daily) for Adelaide for comparison, so your monthly chart is a great help. I am running a detailed spreadsheet with usage and financial analysis which I am happy to share if you are interested.
Some observations: my panel arrangement seems to capture more early and late sun which is beneficial in the winter season and because of the shallow roof angle the penalty is no as bad during summer peaks, so overall I am doing better than I expected.
Location also seem to be a factor, I am in the Adelaide Plains close to the beach whereas my friend who runs a 5.2kW system in an elevated suburb is getting a higher normalised reading.
Despite being home during the day my feed-in ratio is surprisingly between 65...75% during the year. Being an early adopter I am enjoying a high feed-in tariff with AGL. I also have solar hotwater, use gas for heating in winter and an evaporative A/C during summer. This setup covers all electricity usage (peak & controlled load) and gas usage, with a few hundred dollars left in cash.
I paid a high cost ($15,000) for my system in 2011 which was paid off after 5 years and that despite of living in a 1920's cottage which is not optimally insulated.
Conclusion: given today's cheap PV systems (one like mine would be less than $3,000) and the battery storage option, there should be no barrier for most people to start saving on energy costs!