Problem with solar energy production is that it is highly climate dependent.
For example, Tasmania where i live has an average daily window of about 3.4 hours in which PhotoVoltaic panels actually generate electricity.
It's also very dependent on the buyback policies on the grid, I think the NEM (national energy market) in australia is only paying peanuts for energy generated by homes. Hopefully the increase in battery tech assists in this.
RE: Solar: A Hidden Investment