I am looking to find out if when completing PV annual output calculations for a new onsite installation that only conversion and transmission losses based the first year operation meets the requirement? Or is it required to allow for degradation of output over time which happens to all PV panels.  If allowing for that how many years degradation should be allowed.  Would you allow average losses over the expected lifetime of the PV Installation (20 years) or say only over the first 5 years which is applicable to Tier 2 Assets in LEED V4.1?