The 9.8kW solar system is installed in 2018 on top of the existing 3kW system.
The owner sees the benefit of solar that does not only save energy cost, but also earn credit from Feed-in Tariff. When excess solar energy produces, the grid will buy them conditionally and hence give the owner credit. The Feed-in Tariff increased from 5 cents to 11 cents in Victoria since July 2017. It is a good sign for solar system owners.
Additionally the government rebate for small solar is still available, so the investment on solar system become very attractive.