The characteristics of harmonic current emission of residential customers depends significantly on the number of users. While single users have a virtually random behavior, the low order harmonic current of a whole network with several hundreds of residential users usually shows a high level of prevalence with low variation. This paper discusses the aggregation characteristic of low order harmonic currents in residential low-voltage networks based on an extensive measurement database of single users and aggregated users. The first part of the paper compares the harmonic emission of single users and groups of users and shows, how the variation of harmonic magnitudes and phase angles changes with the number of users. The second part presents a systematic simulation of the harmonic currents for groups with stepwise increased number of users. Based on the results, recommendations for the development of probabilistic aggregate harmonic models of residential users are provided.