There are 45 year old solar panels at the Extension office in town.  Still making more than 90% of nameplate a few years ago.

If it wasn’t for tariffs you could buy a 10kW system with inverter and ground mount for less than $6K, spend a couple days mounting it yourself, and then have an electrician come in for a day and put in a subpanel to your meter and wire it in.  I would think all in cost would be less than 8K.  And you would get a Fed tax credit and maybe could still get an IL SREC.

Instead panels are double expensive and last I checked a couple years ago the installers wanted about 40K installed by the time they figured out how much to inflate the price so you could pencil in a 6-10% return on your money net of SREC and  Fed tax credit.