System makes less than in year one. How much loss per year is normal before I file a module performance warranty claim?

Plain explanation

NREL's large field study found an overall median performance loss rate of −0.75% per year, about −0.48%/year in cooler climates and −0.88%/year in hotter ones. Lower output can also come from soiling, shading, inverter faults or a poor year of sun, so rule those out first. A warranty claim is judged against the guaranteed output and measurement conditions written in the module maker's warranty document, usually needing a measurement under defined conditions. Keep monitoring data and serial numbers ready.

Steps from the source

1. Rule out soiling, new shading, string faults and inverter derating
2. Compare yield against irradiance for the same period (monitoring data)
3. Read the module warranty: guaranteed output, test conditions, claim process
4. Collect serial numbers and measurement data before contacting the seller/maker

"cooler climates exhibit a median −0.48%/year loss, which increases to −0.88%/year in hotter climates."

Word for word from the source.

Source

Where installers ask this

• Has anyone claimed performance warranty? (r/solar)
• reddit.com/r/solar/comments/1irt3jm/how_is_degradation_tracked/

General guidance based on the manufacturer's manual or the named source. Always follow the current manual for your exact model and your national code. DC and AC electrical work is for qualified installers only. Not affiliated with or endorsed by any brand named; trademarks belong to their owners.