The efficiencies of six MHD topping combined power generation systems and one gas turbine topping combined system driven by different combinations of fuel and oxidant supply schematics were compared and classified on the bases of overall chemical reaction models for the combustion and gasification processes. The primary fuel was carbon that modeled a coal. The fuel types considered were coal and coal-synthesized gases which were provided by either conventional top gasification or by the tail gasification process. The oxidant was either pure oxygen, oxygen enriched air or air. In the MHD topping cases, the oxidant was preheated to each appropriate temperature. The enthalpy extraction of the corresponding power generation units in the topping and bottoming systems and the temperatures at the inlets of regenerators as well as at the stacks were assumed to be identical in all cases, except the inlet temperatures at the recuperative air heaters and the steam generators. We showed that the tail gasification system with an MHD topping and a combined gas turbine and steam turbine bottoming exhibited the highest plant efficiency insofar as it was based on the state-of-the-art technology of the power generation units and the heat exchanger.