Phase change materials, such as sodium acetate trihydrate, are efficient materials for Latent Heat Thermal Energy Storage (LHTES) according to their interesting thermal properties (high latent heat and specific heat). Their main drawback is a large degree of supercooling, up to 90 K for sodium acetate trihydrate, where the material may remain liquid below its melting point. However, heat could be released if the solidification could be triggered. For a better understanding of how heat is discharged after an initial cooling by external water flow and a solidification induction by seeding, the temperature was experimentally recorded to measure the residual solidification plateau duration. This experiment was repeated for different nucleation temperatures and fit well with the theoretical predictions. An increase of 90% in the solidification duration was observed when the supercooling degree dropped from 35 to 8 K. Thanks to an original experimental bench, this temperature record has been compared with a fully new method allowing the measurements of the material's opacification throughout the solidification process. Finally, two different opacification behaviors were observed for supercooling degrees below and above 20 K. •Solidification behaviors from different supercooling degrees were explored.•The heat release duration was deeply influenced by the supercooling degree.•The T-history method by thermocouple was consistent with theoretical predictions.•Laser opacification method is reliable when considering a low supercooling degree.