How long do solar panels last?
Solar photovoltaics slowly lose their generating capacity. Although some solar panels are still working satisfactorily 40 years after installation, the conventional view is that most will dip below 80% of their rated capacity within about 20 years. This will vary slightly between manufacturers and between different types of silicon.
http://www.scitizen.com/future-energies/how-long-do-solar-panels-last-_a-14-2897.html
>> “How long do solar panels last?” <<
That depends on what type of crystals they have, and how effectively they are darkened.
Most panels are unconditionally guaranteed for 25 years these days.
Most crystals actually can be re-darkened by removing them from the back of the glass face withe solvents (retched vapors) then sticking them back on, which should last for about another 20 years.
PV remains full of unknowns as to ultimately how long they will last. Emerging technologies are bringing improvments in efficiency levels too, so some panels may get replaced for that reason.