Equipment guarantees are extremely important and it is obligatory by legislation to provide
warrantee against product defects. Most manufacturers typically provide a PV module
warrantee of 20 years and 5 years for the inverter.
Most manufacturers offer a supplementary performance warranty for PV modules outlining
in general how the performance will gradually decrease in time. In particular, a typical
performance warranty is that after 20 or 25 years the power output of the PV module will
be 80 % of its original peak power.
Independent performance assessment
Independent PV system performance assessments are becoming very popular in the industry of PV as this is a way to provide a non-biased assessment (carried out commonly by research institutions) of the real outdoor performance of the system.