Measurement
Power loss after stress test
- ID
meas:stress-test-power-loss- IRI
https://solarlattice.org/kb/meas/stress-test-power-loss- Status
- active
- Also known as
- power degradation
This signature is a drop in module maximum power, usually measured by flash testing at standard test conditions before and after an accelerated stress test. In PID lab tests the module's rated system voltage is applied to its shorted leads while the module surfaces are grounded, either in a damp heat chamber or with foil or other conductive electrodes. Modules that lose more than the pass/fail limit in the 60°C, 85% RH PID test have also failed by potential induced degradation outdoors. In bifacial PERC modules, the PID-p loss is much larger when the module is flash tested from the rear than from the front. With longer stress, power can partly recover. Leakage current during the test is only a weak indicator of how much power is lost, so measure power directly. After damp heat or thermal cycling tests, EL images taken with the power measurement can show dark cell edges from corrosion or dark areas from disconnected busbars. Modules with more cracked cells, or with dendritic crack patterns, show more power loss after humidity freeze sequences.
<!-- review notes
- sentence 1: support check: partial - Passages show drops in power measured by flash/IV before and after stress, but 'usually' and 'maximum power' before/after are not explicitly stated generally.
- sentence 5: support check: partial - Leakage current is called a weak indicator of degradation extent, but the advice to measure power directly is not stated.
- sentence 6: support check: partial - EL images show dark outer cell parts after damp heat and dark busbar areas after thermal cycling, but 'taken with power measurement' is only loosely implied; cell edges 'dark' matches, so mostly supported.
-->
Claims
typical_power_loss
c1 verified · fact
≤ 10 PERCENT
Conditions: Bifacial glass/glass PERC modules with EVA after combined-accelerated stress testing with -1200 V bias, flash tested from the front at STC
Reported as almost 10% relative degradation, attributed to PID-p on the rear with a smaller LID contribution.
verified by: review-workflowverified on: 2026-10-20review note: possible conflict with c2 (same source; check the conditions); reviewer: the compiler-flagged conflict is a different scenario or source, not disagreement
c2 verified · fact
≥ 50 PERCENT
Conditions: Same combined-accelerated stress test of bifacial PERC glass/glass EVA modules at -1200 V, flash tested from the rear at STC
Loss looks much larger when the rear is illuminated during measurement.
verified by: review-workflowverified on: 2026-10-20review note: possible conflict with c1 (same source; check the conditions); reviewer: the compiler-flagged conflict is a different scenario or source, not disagreement
c3 disputed
nominal 5 PERCENT
Conditions: One module design that survived a 96 h PID stress test at 60°C, 85% RH and -600 V
The 5% figure is also the pass/fail criterion. Modules losing more than that in this test failed by PID outdoors.
review note: possible conflict with c4 (same source; check the conditions); possible conflict with c5 (same source; check the conditions); possible conflict with c7 (same source; check the conditions); possible conflict with c8 (same source; check the conditions); possible conflict with c10 (same source; check the conditions)conflicts with: Power loss after stress test (c2)
c4 verified · fact
≤ 1.5 PERCENT
Conditions: Complete module shipping stacks after transport simulation per ASTM D4169/4728
verified by: review-workflowverified on: 2026-10-20review note: possible conflict with c3 (same source; check the conditions); possible conflict with c7 (same source; check the conditions); possible conflict with c8 (same source; check the conditions); possible conflict with c10 (same source; check the conditions); reviewer: the compiler-flagged conflict is a different scenario or source, not disagreement
c5 verified · fact
≤ 2.8 PERCENT
Conditions: Modules after transport simulation followed by thermal cycling and dynamic wind load tests
verified by: review-workflowverified on: 2026-10-20review note: possible conflict with c3 (same source; check the conditions); possible conflict with c7 (same source; check the conditions); possible conflict with c8 (same source; check the conditions); possible conflict with c10 (same source; check the conditions); reviewer: the compiler-flagged conflict is a different scenario or source, not disagreement
c6 verified · fact
≤ 5 PERCENT
Conditions: Seven of eight modules of one type after 2000 h damp heat at 85°C/85% RH
verified by: review-workflowverified on: 2026-10-20review note: support check: partial - Seven of eight modules showed less than 5% degradation after 2000 h damp heat, but the passage doesn't give 'up to 5%' as a maximum exactly; roughly consistent though 'less than 5%' vs 'up to 5%' is close; the figure also hints -7% for one module.; possible conflict with c8 (same source; check the conditions); reviewer: the compiler-flagged conflict is a different scenario or source, not disagreement
c7 disputed
nominal 4 PERCENT
Conditions: One module after 2000 h damp heat at 85°C/85% RH
review note: possible conflict with c3 (same source; check the conditions); possible conflict with c4 (same source; check the conditions); possible conflict with c5 (same source; check the conditions); possible conflict with c8 (same source; check the conditions); possible conflict with c10 (same source; check the conditions)conflicts with: Power loss after stress test (c2)
c8 verified · fact
nominal 28 PERCENT
Conditions: Same module after extending damp heat to 3000 h at 85°C/85% RH
Considered overstress. EL showed the outer cell parts completely dark from moisture-driven cell corrosion.
verified by: review-workflowverified on: 2026-10-20review note: possible conflict with c3 (same source; check the conditions); possible conflict with c4 (same source; check the conditions); possible conflict with c5 (same source; check the conditions); possible conflict with c6 (same source; check the conditions); possible conflict with c7 (same source; check the conditions); possible conflict with c9 (same source; check the conditions); possible conflict with c10 (same source; check the conditions); reviewer: the compiler-flagged conflict is a different scenario or source, not disagreement
c9 verified · fact
≤ 5 PERCENT
Conditions: Three of seven crystalline modules from different makers after 800 temperature cycles
verified by: review-workflowverified on: 2026-10-20review note: possible conflict with c8 (same source; check the conditions); reviewer: the compiler-flagged conflict is a different scenario or source, not disagreement
c10 verified · fact
nominal 3 PERCENT
Conditions: Baseline (bias) loss from glass corrosion after mechanical load followed by 200 humidity freeze cycles
On top of this baseline, loss rises with the number of cracked cells.
verified by: review-workflowverified on: 2026-10-20review note: possible conflict with c3 (same source; check the conditions); possible conflict with c4 (same source; check the conditions); possible conflict with c5 (same source; check the conditions); possible conflict with c7 (same source; check the conditions); possible conflict with c8 (same source; check the conditions); reviewer: the compiler-flagged conflict is a different scenario or source, not disagreement
Referenced by
Data