Warranty conditions for c-Si PV modules typically guarantee at least 90% of the nominal output after 10 years and at least 80% after 25 years. Some manufacturers are already providing guarantee for at least 84% after 25 years. These are significant improvements
compared to few years ago, where rather a guarantee of 80% after 20 years was standard. This tendency is expected to continuo with ongoing research and not yet fully exploited potential of reducing efficiency degradation in PV modules, especially when it comes to the optical degradation of the cell encapsulation materials. In this paper it is cautiously assumed that PV modules installed in 2015 will eventually perform at 90% of their initial power after 10 years
of operation and 80% after 25 years. For modules installed in 2030 a 10th year performance at 94% and a 25th year performance at 88% of the nominal value are assumed.