banjar, When you refer to "about 10 years before that ledger even balances" I guess that you are referring to just to get a possible breakeven of power balance cost, that is solar generated power cost, vs purchase and upkeep cost.
However, for a dedicated greenie, the entire manufacturing, transport, installation carbon footprint needs to be taken into account. As far as I recall reading PV manufacture is not a green process, it is quite energy and water intensive.
I am not sure where GM's panels were manufactured or where the final system consolidation was done, but I would imagine significant parts of the process required air transport of various components around the world.
Then of course the installation processs would hardly have been a low-carbon footprint since at the very least a reasonable size van would be needed to transport the equipment and various other aspects also need to be considered.
It seems to me a not dissimilar sitiuation to ethanol production where, despite the high sounding intentions, a larger amount of input energy as diesel/gasoline/water is required to produce a smaller amount of output energy as ethanol resulting in a net energy cost for the whole cycle.
It is more about making the greenie feel good than about actually doing something effective for the environment.
And the enormous cost seems as much to do with a few slick businessmen profiting by exploiting this feel-good factor of the afflicted to sell systems that are marginally suitable at best.
