Point excesses of substances and thermodynamic properties and the role they play in the solvation and binding of counterions in solutions of electrolytes, including micellar systems, are analyzed. A complete system of fundamental thermodynamic equations for point excesses is formulated. Statistical mechanics equations that relate point excesses of substances to the electrochemical potentials and concentrations of components are derived. For ionic micellar systems, a relation between point excesses and charges and concentrations of ions and micelles is obtained. The results are substantiated by direct calculations of point excesses with the use of the Debye-Hückel method.