The proposed paper deals with thermodynamic optimization of highly flexible ICE (variable compression ratio, intake/exhaust VVA) while comparing e-charging concept with classical one. The e-charging concept is based on idea that compressor/turbine has its own electrical machine (motor/generator) and that additional electrical energy can be supplied/attached from/to engine crank train. Hence it allows independent control of compressor/turbine. On the other hand, classical approach is based on a standard mechanical connection between turbine and compressor. The whole system (flexible engine + boost device) is optimized under steady operation – low load (BMEP of 4 bar), medium load (BMEP of 13 bar), high load (BMEP of 18 bar) and full load are considered. Moreover, 3 combustion concepts are considered – classical SI and CI, and ideal RCCI. Sensitivity study of selected parameters is performed: e.g., efficiency of electrical machine(s), HP exhaust volume. All the results are achieved by means simulation using 0-D/1-D SW tool. The data are analyzed and general conclusions are drawn while focusing on thermodynamic potential of e-charging concept under steady operation.