## C1 System Loss Assumptions

In PVWatts, a single derating factor is used to cover a variety of system inefficiencies. The compliance software uses slightly different assumptions for this derating factor as described in the table below:

Loss Type | Value | Differences from PVWatts default assumption
Soiling | 0.02 |
Shading | 0.0 | Modeled explicitly
Snow | 0.0 |
Mismatch | 0.0 | Mismatch from shading is characterized using SIF
Wiring | 0.02 |
Connections | 0.005 |
Light-induced degradation | 0.015 |
Nameplate rating | 0.01 |
Age | 0.05 | Estimated 0.5% degradation over 20 years based on these references: [1, 2, 3]
Availability | 0.03 |
Total | 0.14 |