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 |
|
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 |
|