Electrohydrodynamic (EHD) flows are of great interest due to their capability of intensifying the heat exchange. However, the electric conductivity of liquid is typically disregarded and the model of unipolar injection is used. This paper studies the effect of liquid conductivity on the efficiency of an EHD heat exchanger with charge formed by injection as well as field-enhanced dissociation. The investigation involved computer simulation of the complete set of EHD equations supplemented with that for the heat transfer. The range of low-voltage conductivity of working liquid, when electroconvection can be used for heat transfer enhancement, was estimated. The EHD heat exchanger based on the field-enhanced dissociation is shown to be very promising for dielectric liquids with heightened conductivity.