<p>The electrohydrodynamic instability of perfect and leaky viscous dielectric fluids has been discussed when direct and alternating current fields are present and the porous medium is saturated. The dispersion relation is derived for the AC (alternating current) and DC (direct current) fields by employing the linear stability treatment with the perturbation amplitude’s time dependency and Floquet analysis, respectively. The stability discussion has been established according to the dispersion equation’s root-finding solution in the two cases under perfect and leaky dielectrics. The parameters effects on the system’s stability have been shown through a variety of numerical applications. It is observed that, in contrast to the direct current (DC) fields, alternating current (AC) fields act to dampen system instabilities. Moreover, when the interface is perfect-leaky dielectrics, the system is less stable than when it is leaky-leaky dielectrics. Also, the system is not influenced at the perfect-perfect interface for DC fields, but becomes more unstable at the perfect-leaky interface when a porous medium is present. Interestingly, the frequency as well as the ratio of viscosities has irregular effects on the stability. The medium permeability has a destabilizing impact on the model for all studied cases. By creating appropriate devices that regulate the model parameters, the current study may be helpful in enhanced oil recovery, fuel cells, emulsion separation, water filtration, and its desalination.</p>