A method is proposed to estimate the characteristics of the power flux supplied to an anode and a cathode in Ag-SnO2 submitted to an AC electric arc with a maximal value of the arc current intensity about 400–500 A and an arc duration about 4–5 ms. It is based on the one hand on the observation by optical microscopy and Electron BackScatter Diffraction (EBSD) of the area melted by the arc, thus making it possible to evaluate the depth and radius melted, and on the other hand on a thermal modelling allowing to estimate an equivalent voltage (proportionality coefficient between the intensity of the arc current and the received power) and the power flux surface density.