A mean field approach is proposed to derive the electrical interaction energy for a system containing arbitrarily shaped, ion-penetrable particles bearing fixed charges in an electrolyte solution. We show that this energy can be decomposed into the product of two terms. One of these terms is a function of particle properties, and the other term is independent of particle properties. The electrical interaction energies of spheroids and tori are evaluated. Numerical results are presented to show that arbitrary assumptions concerning the shape of a particle can lead to a significant deviation in the estimation of the electrical interaction energy. Care must be taken in estimating the properties of a particle on the basis of the electrical interaction energy.