Nimesh Katariya Light Induced Degradation (LID) is the initial power loss in PV modules during the first weeks of sunlight exposure. PERC: 1.5–2.5% LID. TOPCon: <0.5%. HJT: <0.3%. Accounted for in 25-year warranty calculations.
Key Takeaways
- LID = initial PV module power loss under first light.
- PERC: 1.5–2.5%. TOPCon: <0.5%. HJT: <0.3%.
- Manufacturers spec year-1 power ≥ 98% to account for LID.
- TOPCon/HJT advantage in cumulative 25-year output.
How LID Plays Out in the Field
LID is a stabilization event, not an ongoing decline. A PERC module rated at, say, 540 W at the factory will typically settle to roughly 527–532 W within its first few weeks of outdoor exposure as the boron-oxygen defect reaction runs to completion, then hold that output going forward. Because the effect is well characterized and repeatable across a given cell chemistry, manufacturers don’t treat it as a surprise — they set the year-1 power figure in the performance warranty to already reflect the post-LID, stabilized value, so every subsequent year of the 25-year warranty curve is measured against that lower baseline rather than the factory nameplate.
This is also why cell technology matters more here than most buyers expect. Since the boron-oxygen mechanism is specific to boron-doped p-type silicon, switching to an n-type cell architecture such as TOPCon or HJT removes most of the reaction rather than merely reducing it — which is the reason TOPCon and HJT modules are quoted with LID figures an order of magnitude below standard PERC.
Related Reading
LID is one of several first-year loss mechanisms that a bankable energy yield simulation has to account for before a lender will sign off on a project’s output forecast — alongside the slower, temperature-driven degradation covered in LeTID and the long-term annual degradation rate that governs years 2 through 25. Because P50/P90/P99 yield reports are built on year-1 output as the baseline, understanding what’s already been absorbed into that number — versus what still needs modeling — is worth knowing before reading a report like the one described in P50, P90, P99 in Solar Yield Reports — A Lender’s-Eye View. Module selection decisions that weigh PERC against n-type cells for LID exposure are typically made during the same Solar 3D Pre-Design stage where shading, layout, and yield simulation are worked out together.
Frequently Asked Questions
4 commonly searched questions about LID (Light Induced Degradation).
What causes LID?
Is LID a one-time loss or does it keep recurring every year?
Does LID show up separately on a module datasheet?
Why do TOPCon and HJT modules have so much less LID than PERC?
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