[jyl]

What is a realistic lifetime for a residential PV grid-tie system (w/o batteries)? 20 years? 30? What wears out?

Is there any maintenance required, or is cost literally zero after year 1? I would think you want to hose off dust and leaves now and again? My roof is three stories up and I'm not sure how I'd do that - have images of having to build a hatch in the center of the roof and plumb water to a rooftop hosebib - sounds weird.

Is is correct that, w/ current module design, a shadow on one part of the module (say, a leaf), reduces the output from the whole module?

How can one estimate how much sun a given location gets per year? I assume latitude, climate, panel direction/angle all factor into it. Assume no shadows from trees/other buildings. Is there a online calculator where I can plug in a location and get a reasonably decent estimate?

It looks like James, your scenario equates to 6 hours/day of full sun - but that's got to be specific to TX and similar South/SouthWest locations?