Solar in Seattle starts on a roof the long wet season has already been testing. Moss, fir shade, and months of cloud are the facts. A south slope under tall cedars in Ravenna or a west slope of townhouses that shade each other is not an open field. The first subject is the deck and the covering. Soft bays, active stains, and shakes or shingles that are already tired are reasons to talk about the roof before anyone talks about modules sitting on it for years.
Say what the surface is and which way the clear plane faces. Composition, cedar, or a low membrane on a newer infill all attach differently, and a flat roof holds water in this city in a way a steep bungalow slope does not. Ask how the feet get flashed so November rain does not turn each bracket into a ceiling stain. Skip sheathing on an old house may not hold a mount. If you can see the attic, say whether the wood is dark after a week of drizzle.
Ask where an inverter would sit in a house that is already short on dry closets. A crawl that smells like wet soil is a poor neighbor for the equipment. Ask, separately, what you want on the uncommon day the utility lines are down. Shade from late morning through afternoon is the fact the call cannot skip. A slope is not clear just because a map says it faces south, not when the firs own it.
Limbs and moss do not become polite because hardware is up there. Ask how a later repair happens with modules in the way, and what must be approved before work starts if an association or a permit office is involved. You are not drawing a rack on the phone. You are deciding whether this wet roof can carry the equipment.
Stand on the sidewalk, look at the moss line and the trees, and call with the neighborhood before a drawing made from the sky talks you into a bad deck. Either this wet roof can carry hardware or the first call is about the roof itself. Call the number on this page.