The problem with the solar panels is their duration. Only 10 years for the undulators and 30 years for the photovoltaic panels.
The cost for an installation that provides 6 kWc is $19 620, while it will allows about $1808 of savings per year, i.e. $18 080 over ten years.
So, this is a loss of $1540 comparing to the intial investment. We will have then to invest again, and also to pay for the maintenance.
The solar panels are not yet enough good with the rentability and efficiency.