The parametric evaluation of the variables that define the operation of a charge injection electrostatic atomizer is described in terms of the electrical performance. Here atomizer performance for smaller orifice diameters and more viscous liquids than previously investigated is presented. The response of the injected current as a function of atomizer geometry, coupled to an analysis of the empirical charge injection laws, is used to relate the electrohydrodynamics with more well-established studies in quiescent liquid. Evaluation of spray and leakage current to injection current ratios are also used to determine the electrical efficiency with a view to locating the optimum operating conditions as a function of atomizer geometry and applied bulk flow. The optimum electrode-to-orifice diameter ratio in previous work is confirmed, and the relationship between the spray specific charge and the maximum electric field on jet surface at a critical point of operation is extended to charge injection atomizers of small orifice diameter.