Re: GREAT DISRUPTIONS AHEAD(MattZN)
No, they usually install them flush with each other on rooftops. You can google pics. I've seen large unspaced matrixes 20 panels across and 5 high on roofs. DC panels basically don't fail so there's no maintenance really needed. You just wash the panels down once or twice a year to clean off dirt (as a home owner).
(I don't recommend getting panels with built-in micro-inverters. Standard mount-and-forget DC panels are the best way to go).
Utility-scale is different, but the calculations are about the same (or better) because the utility-scale panels are usually on trackers and spacing is optimized for maximum production across the whole day.
-Matt
edit: Also, utility scale will probably wind up using concentrators and multi-junction cells in volume soon, so we're talking MUCH higher efficiencies for the sun collection area. 30% non-concentrated and 40% efficiency concentrated.