The length of time that a solar panel lasts is something that is of obvious concern to you if you are thinking about buying solar panels for your home.
In answering this question it is necessary to discuss the different types of solar panels as they are each likely to have a different working life.
The first type of panel is the amorphous, thin film silicon solar panels. These have the distinction of being both the least efficient and the least expensive panel you can buy.
These solar panels still usually come with a 25 year warranty but usually they are only warranted to produce at 80% of their maximum rated output after 10 years. I don't think anyone really knows how long these solar panels will last in real life and many manufacturers of this type of panels have already stopped making them. It is my gut feeling that these panels will last the least amount of time and have the shortest working life. The reason I say this is that amorphous silicon in other applications tends to break down relatively quickly and I would expect this to also be the case in solar panels where they are exposed to the UV radiation.
Most of these solar panels have 25 year warranties and I have seen many solar panels of these types that are more than 30 years old still working quite well.
I don't think there is likely to be any difference between monocrystalline and polycrystalline solar panels when it comes to how long they last.
I think consumers can be confident about these panels lasting at least 25. The reason I say this lies in the core make up of the cells. Crystalline cells are made from wafers that are in turn cut from silicon crystals (that are hard rocks). Given these are then covered by glass (or other clear covering) and protected from water and wind (the normal things that weather rocks) I think it is very likely that these cells could last 50-100 years.
In fact with crystalline solar panels I think it is more likely to be failure in the components around the core cells that may be determinative of how long the solar panels last. It is more likely that water ingress from the failure of seals, cracking surface covers or failed junction boxes will lead to the demise of these solar panels long before the cells have decayed in any real sense.
So in many ways the working life of a solar panel may be determined by the quality control of the manufacturing process rather than by the technology of the solar cell used in the panel.
From a consumers perspective the answer to the question, how long do solar panels last, is a piece of financial information they need to know to make a decision about the attractiveness of a solar power system for their home as an investment.
Most solar calculators work on a working life of 25 years but this figure is used more because it is the length of the bankable warranty rather than the full working life of the panels. I think in practice this analysis short changes solar as an investment.