Rice, that is a tough question. What is the value of a silent evening, miles from anyone else, sitting with my wife in camp chairs outside the trailer, watching a meteor shower without the sound of the generator? How much would I pay NOT to listen to a generator?
I can tell you that we go to a lot of trouble to boondock in total isolation, so maybe you could use the labor expended in that process as a substitute for the market value of the silence itself?
Pick a number.
Now multiply that one-time value by the total number of nights I have been able to avoid using my generator. Hundreds of times??
I think that my point (and there must be one in here, somewhere) is that the intangible and unquantifiable benefits of solar are far greater than the actual dollars involved. I won't say it is infinite -- if someone offered to pay me a million dollars to miss that quiet evening and listen to a generator instead, I would do it.
But not for a hundred dollars.