I took an introductory class about solar powering one’s home at TxRx Labs. It was very well done — I learned quite a bit about maximizing energy and the difference between a cheap controller and an expensive one (hint: the features included in the expensive version are necessary if one is serious).
One of the topics that kept coming up was ROI (return on investment). How long before you “pay off” your system by selling the electricity to the grid? There were all sorts of charts and the like provided on what kind of system, how big the panels, etc.
I realized that I don’t care. My goal in going solar isn’t to make money or pay off anything. It is simply to take that expense out of my life forever (or for several decades). I won’t have to worry about running my A/C during the summer and getting a massive bill. I won’t feel cheated because I have to pay $30 for the cost of the lines and poles on top of my usage (which often falls below the “minimum” amount, so I get a mandatory fee on top of that).
To a lesser extent, I’ll feel a bit more treehugger-ish because I’m not relying on dirty power generation. If I can add enough capacity to charge an electric car (or at least top it off), that’s even better.