EL testing is one of the most effective tools for identifying microcracks and internal cell fractures, especially when damage is not visible and has not yet produced obvious thermal hotspots. While infrared imaging is excellent for identifying active hotspots and thermal anomalies, EL testing can detect internal damage earlier in the failure timeline. UV fluorescence testing is strong for identifying material and encapsulant degradation, but EL provides deeper insight into cell level damage and electrical integrity. For many sites, EL testing offers the strongest diagnostic value when combined with visual inspection and infrared testing to create a complete picture of module condition.