The harmonics generated by DER devices can cause distortion in power system voltages and currents. In addition to the power quality issues, loss, and component failures harmonics can have an economic impact on distribution networks. In this paper the authors analyze harmonics produced from multiple sources such as solar, wind and energy storage systems. The aim is simulating harmonic interactions that can lead to concern in distribution networks. Accordingly, a new index for harmonic analysis is proposed to simultaneously consider magnitude and angle of waveform. The effect of generated harmonics from DER is evaluated quantitatively on distribution circuits with the help of data visualization approaches. Harmonic propagation is simulated in a detailed distribution network model to analyze how circuit topology varies harmonics effects. Due to the interaction of different harmonic sources, the sensitivity analysis is conducted to show the impact of each harmonic source magnitude and angle on the overall distribution network total harmonic distortion. Phase balancing impact on harmonic distortion in distribution networks is also considered. (C) 2013 Elsevier B.V. All rights reserved.