I'm in Canada not the US. I had relatives get rooftop solar, bigger system but not significantly (I think around 10kW). It took them 2 or 3 days to do the insta

I'm in Canada not the US. I had relatives get rooftop solar, bigger system but not significantly (I think around 10kW). It took them 2 or 3 days to do the install for a crew of ~6 (over 2 trips), plus another 3 visits by the contractor and a utilities inspector - once beforehand, once following mounting system and wiring install, and a third time following completion before it could be connected. Don't know material cost, but the full system was somewhere around $40k (I guess that's Canadian $, so subtract a few $ to get USD). This was with an asphalt shingle roof, so it'd be more for metal or tile. You could ask your BIL if the estimates he received had any breakdown. Edit: there may have been an electric panel or service upgrade rolled into my relatives cost