A three-dimensional mathematical model was developed for calculating joule heat release, glass flow, and heat transfer in electric glass furnaces. The model developed here allows for multiple electrodes, multiphase firing, and for the feeding and withdrawal of molten glass. The model is fairly general with respect to the arrangement of the electrodes, the firing pattern, and the choice of the boundary conditions, and it allows for the temperature dependence of the glass properties. The model was used to calculate electric potential, rate of heat release, flow pattern, and temperature distribution in the melting of flint and amber glasses in an all-electric melter with side-entering electrodes. The calculations were performed for the industrial conditions of pull, power, and the electric firing scheme. The bulk glass temperature was found to be very uniform with large temperature gradients near the boundaries. The calculated flow pattern was, in general, quite complex with several circulation loops. The temperature and the maximum velocity for the amber glass were found to be higher than the corresponding values for flint glass.