Due to single-phase connected loads and distributed generation, distribution networks often operate under unbalanced loading conditions. This implies that the assumption of a balanced network for the purpose of state estimation does not always hold. Numerous papers have been published on the topic of three-phase state estimation in distribution networks in order to solve this problem. However, there is no generic method to determine whether a three-phase state estimator is required or if a single-phase network representation can deliver a sufficient degree of accuracy. Therefore, in this paper a new method is presented that provides a generic method to choose between the single-and three-phase state estimator method, depending on the network topology, and metering configuration.