You also have to keep in mind that the site will dictate how many solar hours you are going to get in a day.   You will want a site analysis done to see what shading you will experience through all 4 seasons to determine if the site will be impacted.  You also will want to go out and look at the online resources that tell you what the solar hours are for the location where you want to put the solar panels as that is a best guess on what you will likely get providing there are no obstructions or things that are going to cast a shadow on the panel install. 

Then boil it down to what is realistic for the location.  So let's say it boils down to 5 good hours a day, then do the math.  More hours typically in the summer time, less hours in the winter.  Again anything you over produce will get sold back to the power company, and then you end up buying it back after you don't have the sunlight anymore.  Depending on the utility company and state the rates can vary greatly.  I know in my location I would be selling back at wholesale and buying at retail so it makes no sense to over produce anything. 

Economically it didn't work out to make sense from a pure mining perspective for me based on my own situation.  I think once you run the numbers you will have to decide if you are doing this for reasons other than mining and if it is worth it to you for your own situation.