Solar Lattice

Mitigation

Initial degradation in yield model

ID
mit:yield-model-initial-loss
IRI
https://solarlattice.org/kb/mit/yield-model-initial-loss
Status
active

This action means building the expected initial light-induced power loss into the energy yield model, so that early stabilization losses are not mistaken for faults and do not inflate production forecasts. It addresses Light Induced Degradation (LID), which appears as a drop in STC power, short-circuit current and open-circuit voltage early in system life, with no visible defect. If initial degradation is under-estimated, energy yield predictions and investor expectations are directly affected. Some yield assessors add a separate initial LID term to the long-term yield prediction, sized by module technology and site location. The size of the allowance must match the technology: crystalline LID is a few percent in the first days, amorphous silicon can lose much more over the first months, and some CIS modules actually gain power. LeTID is harder to model because it develops over years, depends on module temperature and site, and may not recover within the module lifetime. There is no consensus on which degradation values to use, so pair this action with low-LID module selection, and check unexpected early losses with IV and flash testing.

<!-- review notes

Claims

typical_power_loss

c1 verified · fact 0.3–1 PERCENT

Conditions: Initial LID term some yield assessors add in long-term yield predictions; depends on module technology and location

verified by: joshuahamsaverified on: 2026-10-20review note: reviewer: the compiler-flagged conflict is a different scenario or technology, not disagreement

c2 verified · fact 1–2 PERCENT

Conditions: First-year drop commonly assumed by PVPS Task 13 survey participants in long-term yield predictions

verified by: joshuahamsaverified on: 2026-10-20review note: reviewer: the compiler-flagged conflict is a different scenario or technology, not disagreement

c3 verified · fact 1–3 PERCENT

Conditions: Boron-oxygen LID in p-type crystalline silicon modules, within the first days of sun exposure

verified by: joshuahamsaverified on: 2026-10-20review note: reviewer: the compiler-flagged conflict is a different scenario or technology, not disagreement

c4 verified · fact ≤ 10 PERCENT

Conditions: LeTID in susceptible modules (first seen with PERC), adding to the LID loss over years

verified by: joshuahamsaverified on: 2026-10-20

c5 verified · fact 10–30 PERCENT

Conditions: Amorphous silicon modules within the first months of outdoor exposure (Staebler-Wronski effect)

verified by: joshuahamsaverified on: 2026-10-20review note: reviewer: the compiler-flagged conflict is a different scenario or technology, not disagreement

Referenced by

Data