I have been toying with the idea for my properties and based on crude analysis it may cover it's costs with the current level of subsidies. The most expensive time of year for electricity costs I find is winter when the tenants use heaters - summer is no problem as I have installed very efficient evaporative air-conditioners. Solar is most efficient in summer and least efficient in winter so it produces the least when I need it the most. The biggest thing though is I have heard that here in SA electricity is expected to double within 5 years - in this scenario it could really pay off.
The questions I have though is what annual maintenance is required? What is the ongoing costs? These are questions that I have to look into.
I also believe that you need to clean the panels at intervals so that they can maintain their best efficiency.
Reality is you can probably install a smaller system initially 1.5 to 2 kW system (getting the solar rebate) and the best value for money system and expand it later. I think in this case though you have to be careful that the system you get has an inverter that has sufficient capacity to expand.
Lastly I think you have to be careful with who you go with as there are some dodgy operators out there, also you have to be very careful and know what you are getting.
