My 15.12kW solar/4 powerwall system was a two day install and they both happened at the same time. They had two electricians who worked on installing the powerwalls, running the conduit, and installing the inverters and the other electrical panels. Then there was a team of 5 or 6 guys working on the roof installing the panels.
As I recall they got all the panel mounting hardware and about 3/4 of the panels mounted on the first day as well as the powerwalls mounted on the wall and the inverters and electrical boxes installed. They got as much of the new wiring done as possible in the new boxes, then they cut my power for a couple of hours at the very end of the first day to finish getting everything connected.
The second day was spent mounting the rest of the panels and running and connecting the DC wiring, then commissioning and testing the system.