This paper presents a method for determination of the finite-element method model electrothermal parameters in a medium-voltage switchgear cell. The research includes a thermal calculation that is considered as a consequence of the eddy currents phenomena, which is a coupled numerical problem. Calibration of the numerical model is based on the multiobjective optimization procedure, which is carried out with the differential evolution algorithm (DE). The DE provides the best possible agreement of the measured temperature values on the test model and calculated values with the equivalent numerical model. The presented results are obtained for the linear and nonlinear case of eddy currents phenomena. The goal of the calibration is to determine the correct electrothermal parameters.