This paper presents the outcomes of a study of the summation of supraharmonic (SH) currents from electric vehicle fast-charging stations (FCS), based on a field measurement in an installation with four 350 kW FCSs. FCSs can contribute to SH emission, between 2 and 150 kHz, in the network and their impact on the grid is quantified by the summation of SH components. Little is known about the summation of SHs in an installation with a power of hundreds of kW, therefore this article aims to contribute to the understanding of the SH current emission and their summation in practice. The results show that the total SH current from the installation increases with the number of active chargers, but not monotonous and that the emission is not constant over time. A diversity factor is proposed and the relation between total and summed current is analyzed to provide further insight into the role of absorption by other chargers. The findings are a step towards modeling the SH summation for FCSs and other installations with large power-electronic devices.