Solar in Pittsburgh is a steep roof aimed by the hill, not by a clean compass. Streets run where the slope allowed, so a surface may face a neighbor's ridge, a valley, or a stand of trees uphill. Snow slides. Ice sits at the eaves. The structure already carries winter before a rack is added. If the covering is old, or the attic already shows ice-dam stains, the roof comes first. A flat row roof is not the picture, unless that is truly what you have. Say pitched, and say how steep it feels from the street.
Shade is the hill's shade. Trees above the house, a dormer, and the next house up the step street can cut the afternoon. A layout that dumps sliding snow onto steps or onto a porch roof is a bad layout. Valleys and lower roofs need to be named so rails do not fight the water. Flashing has to survive ice, not only a summer rain. The electrical service in an older house is often a crowded basement panel on the walk-out side. Say what you have seen. Do not invent a size.
Access is steps and grade. Anyone who looks at the roof needs to know there may be no driveway to the eave. Say that. Ask who pulls the permit and who files the interconnection. Ask how the rack is flashed to the material you have, slate or shingle, and what happens to the modules when that material is replaced. Ask who owns the equipment afterward and who is called when an inverter goes quiet. Leave money out. Snow cover is the climate, not a surprise.
Have the directions the slopes face, what shades them, and whether ice dams are a habit of this house. A photo from far above has not stood in the attic or watched snow leave the eave. If a lower roof catches that snow, say so. It is part of where hardware must not go. The hill will still be the hill after the array is up. Describe it that way.
A level parapet between row cornices is a different city. Solar in Pittsburgh is pitch, snow, shade from the slope, and a wire in an older house. Call the number on this page.