In the field of electrical machines, the finite element method provides accurate results but requires a high computational cost to perform, with sometimes weeks of computations. Therefore, model order reduction methods such as the proper orthogonal decomposition combined with the discrete empirical interpolation method are able to speed up the solution of the finite element problem. To use the obtained results for predictive computations, an error estimator is required.However, the different estimators found in the literature do not apply to our problem. Therefore, a simple error indicator that can be applied to a wide range of problems is proposed in this paper. KEYWORDS discrete empirical interpolation method, electrical machine, error estimation, finite element method, model order reduction, proper orthogonal decomposition Int J Numer Model. 2018;31:e2277.wileyonlinelibrary.com/journal/jnm