As a Sydney resident who went the PV cell route I was interested in your analysis. I did my sums before we decided and we quickly realised that at current rates we would never get our investment back. However, as we both had strong environmental philosophies we decided that for the sake of the environment alone it would be a good thing to do for basically the cost of a 2-3 week overseas holiday.
Our 1.8kW system after rebates and REC's cost us $10,440. The meter installation was $275 only, no further costs.
Our normal electricity consumption is around 2500 kWh/pa, water heating is solar and gas is not installed. In the 3 months since it was installed, the excess generated from the PV system has averaged around 2kWh per day and so each quarter we get a cheque from our electricity supplier. I would expect in summer the difference between what we use and what we generate to be greater and therefore this average should be higher on an annual basis.
The benefit: The psychological impact that the PV system has had on us surprised us both - the feel good factor is amazingly strong. Being very environmental citizens we have donated reasonable sums over time for various causes but you never new how effective that money was but with this installation you can see it delivering clean electricity every day.
Finally what I didn't really think much about was future electricity price increases. They have just announced that electricity prices in NSW will be increasing by around 20% in July - without never having to have an electricity bill again this sort of news also increases also has a nice sound to it!
This was one direct way we could do something about global warming - we long ago gave up on Governments doing anything significant about it.