I replaced original builder's grade asphalt shingle roofing on my house when it was 27 years old. The roof was not leaking.
Most of the roofing damage due to age happens on south slope because of exposure to heating cycles.
Since PV panels are installed on the south facing slope, the assumption that at 20-years mark roof will be leaking IMO is not realistic, especially because contemporary roofing materials have significant quality improvements. I really do not believe in proposition of replacing functional roof with functional solar panels, when an owner can just renew his sgreement with Tesla/Solar City, and likely on better terms.
I appreciate the personal experience anecdotal and the theory that PV panels on (a portion) of south facing would do the trick for making those PPAs renewable outside 20 years.
Being the data analyst that I appreciate from your posts, I'm sure you'll forgive me if I defer to the law of averages:
Asphalt roof average life: 15-18 years ; dimensional 24-30
Asphalt shingle - Wikipedia
I do think people CAN extend the life- I don't think my experience says they do (multi-home owner similar to Audubon - and agree with his post on the issue). Regardless- I very much doubt the value of those PPA renewals beyond actuarial periods will hold water (pun intended- sorry) in the financial marketplace. If I was Tesla I wouldn't risk that assessment- especially since my mission is now clearly to make sure all those roofs get replaced long before that if possible-
And if I'm an investor in TSLA (and I most certainly am)- my model brings the NPV of any PPA or lease beyond the actuarial life of the roof (even if partially covered by existing panels) to zero - and I believe that's what many current analysts are driving at. This is most especially true since for the first time in history the actual effect of the transition on the value per kWh of electrical power is at best uncertain (and certainly headed the wrong direction for the value of my 20-30 year PPA).
Fortunately EM has stated a clear transition to buy/loan financing and away from PPA (lease by 3rd party with time alignment also OK). And so I believe he has this issue in mind and will over time sell off those PPAs making them a small issue or a non-issue. I'm not worried about it given his statements- but continue to watch and believe this transition will help the underlying confidence of Tesla/TE. Anyway- we'll likely have to just disagree on this one- much appreciate the conversation