Solar Panel Degradation: What's Normal and What Isn't
Every solar panel degrades over time, but 'fast degradation' usually means something else is wrong.
Output changes can reflect aging, weather, shading, soiling, or equipment issues. Your module's warranty defines its own power-output terms.
Spec degradation rates
Power-output warranties vary by model and may specify laboratory test conditions. They aren't a promise of a fixed annual energy yield at your property. Check the exact warranty for your panels.
Real-world degradation rates
Soiling and output vary from system to system. Check visible buildup, panel cleaning instructions, and monitoring data under similar weather conditions. Cleaning isn't guaranteed to cover its cost, and a thermal image isn't an electrical diagnosis.
Why soiling is usually misdiagnosed as degradation
Dirt and debris can block sunlight, but the effect varies with the amount of buildup, panel tilt, rainfall, shading, and equipment condition. We don't have a verified typical loss figure for San Diego homes. Compare monitoring data under similar weather conditions before and after cleaning rather than expecting a fixed percentage gain.