On the ground
Philadelphia's rowhomes and the older stone farmhouses out through Chester and Bucks counties put two very different roofs in front of us on the same day. A flat or low slope rowhome roof in South Philadelphia needs a different mounting approach and a tighter penetration seal than a steep slate roof out in Chestnut Hill or Doylestown, and both show up on the schedule regularly.
Philadelphia's Historical Commission adds a layer of review that towns further out in Lancaster County don't bother with, so timelines on historic properties run longer no matter how straightforward the install is. Winters here bring real snow load, heavier than anything South Jersey sees, which changes how inverter placement and rack spacing get handled on anything installed north of the Mason Dixon line.