Well, my panels installed 2005 are just now coming down. Needed a new roof and figured it would be crazy to reinstall the old ones with maybe 5 years left. The current 20 year old panels are probably running 85-90% of installed power. Now new panels have much higher efficiency than my old ones, so the same area is going to make around 2X what my old ones did. As to size, maybe 1/2 my roof is covered and I expect near 0 net with the new panels. Just a tad under, but the way rates work here, overproducing gets no dollars. They will only discount. Credits are only forwarded to the next month bill. And I believe for a max of 1 year and then it goes away. So in this case, the panels outlasted the roof. Panels are much tougher than shingles in hail.