In this paper a method is described which allows estimating the power flux brought by an electric arc on the electrodes. This information is highly important for the understanding of contact erosion mechanisms, as well as for the practical choice of appropriate materials and sizes in switching devices applications. Our method is applied to the case of Ag-SnO 2 electrodes. Compatibility conditions between experimental values of mass loss in well-defined situations and numerical calculations of melted/vaporized metal lead to a maximum surface power density of 8×10 9 W/m 2 for cathode and 2×10 9 W/m 2 for anode. Moreover it is found that less than 16% of the total power brought to the electrodes contributes to metal phase changes.