The formulas for rearrangement energy of solvent were derived by using dielectric continuum approximation. The conventional formula for the rearrangement energy of solvent was corrected for the absence of solvent inside ions. The effect of supporting electrolyte on the rearrangement energy of solvent was discussed. The discrepancy between the calculated rearrangement energy of aquocomplex and experimental one was interpreted in terms of breakdown of adiabatic electron transfer.