An approach to describe equilibrium properties of liquids with electrostatic interactions is proposed based on the combination of computer simulation, optimized cluster theory, and the theory of integral equations. The computer simulation is carried out only for the short range part of the interaction potential. Then, these results are used for the description of the reference system and for the renormalization of the long range part of the interaction, which is treated either by optimized cluster series or with the help of integral equations. This approach avoids the difficulties connected with a proper treatment of the long range electrostatic interaction in the computer simulation. The usefulness of the method is demonstrated for BJH water as an example.