In order to maintain good power quality, Distribution System Operators (DSOs) must keep harmonic voltage levels under limits specified in standards. These harmonic voltages result from non-linear equipment connected in installations, which inject harmonic currents into networks. To implement emission limits per installation, DSOs need to have an accurate and reliable indicator to assess the harmonic emission of an installation. In the literature, some authors propose to use the harmonic active power as this indicator. In this paper, a study is carried out on the use of the harmonic active power to locate harmonic sources on the network and assess the harmonic emission of an installation. It is demonstrated that harmonic active powers cannot be used when there are several harmonic sources connected to the network.