Doing what your doing on your dock makes sense to me. I can justify small jobs like that. For example if I would have done my barn. Could have also used it to trickle charge lawn mower battery, trollin motor battery etc.
Duck river in TN had a new thing where they built the solar field and then sold half panels to customers for $600.00
It only works out to an average of $3-$6 bucks per month in energy savings on your bill each month. Most folks will not go for that. Average 10 yrs to get your money back.
I will have to wait till this stuff decreases in price quite a bit before I will ever be able to make the plunge on a large scale. I would still like to do what your doing buckshot. In the future I am going to redo an outbuilding I have and add some machine sheds to the side of it. I just want to have around 3 light bulbs so I can have some light if I need it. I will go this route to save having to run electricity all the way to it.