The equilibrium profile of a dielectric droplet originating on an insoluble charged nucleus in an external uniform electric field was found. The relationships obtained in three orders of the perturbation theory with respect to small deviation from the non-sphericity describe combined field effects of the charged nucleus and the external field in the coordinate system related to the mass center of the droplet. The dependences of the chemical potential and the work of droplet formation on the number of molecules in the droplet, the surface tension, the permittivity, the nuclear charge, and the strength of the external electric field were determined in analytical forms. The influence of the resultant electric field on the threshold value of vapor supersaturation and the activation energy of heterogeneous nucleation was considered. Thermodynamic relationships that allow us to verify theoretical self-consistency were discussed.