[Spinner77]

Followers of this thread might be interested in knowing that the printed June issue of Choice magazine carries an article on payback periods for solar.

On account of copyright, I have to be careful. A lot of public libraries subscribe to Choice, so you can research the article there if you are interested.

But it looks as if they have had some serious modelling done for a 2.0kW system exporting 30 per cent and 50 per cent respectively. I say it is serious because they seem to have taken most of the things into consideration that you might expect from a professional accountant. That includes the time value of money (discount rate), degradation of the system, increases in the cost of electricity (assumed to be 0.25%) etc. There are said to be 15 variables in all.

Choice does not provide numbers on the payback period, but gives readers a bar chart. The winner looks to me to be the NT, where the payback time is 4 years (for exporting either 30 or 50 per cent). The longest seems to be Victoria: payback looks like up to 10 years (50 per cent export) and about 6-8 years (30 per cent export). In NSW the maximum payback period appears to be around 9 years (50 per cent), and about 6-7 years (30 per cent). SA is a maximum of just under 8 years (50), and about 6-7 (30).

The message I get from the article is to minimise your export to the grid. The differences between the 30 and 50 per cent export scenarios are significant (except in the NT, and - wouldn't you know it? - the ACT where the payback periods do not seem affected by the power exported). Accordingly, the article seems to favour smaller systems.

My personal reaction is that one criticism of the analysis could be its very conservative assumption on increases in the price of electricity.