Voltage unbalance emission allocation principles prescribed in IEC61000-3-13:2008 Technical Report utilise a factor, kuE, which allows separation of the total voltage unbalance that arises at a point of evaluation due to both the load under consideration and the supply network. As per the definition given, this factor (kuE) accounts for the unbalance emission that arises due to the load whereas (1-kuE) accounts for unbalance that arises due to the network. The technical report prescribes a range of values from which a suitable value can be chosen based on the system characteristics, however, no systematic methodologies exist to-date to determine the kuE factor. Hence, the sensitivity of the kuE factor to various system parameters cannot be examined. The work presented in this paper examines the sensitivity of this factor to system characteristics covering line asymmetry, load type and the level of load unbalance. While giving a systematic methodology for the evaluation of kuE it is demonstrated that the use of a constant kuE factor as given in IEC61000-3-13:2008 can lead to erroneous outcomes under certain conditions.