Internally heat-integrated distillation columns (HIDiCs) need heat transfer between the two column sections. Intermediate condensing and reboiling of the rectifying and stripping sections favor the reversibility of the separation process and lead to the increase of heat loads for the two sections but the heat transfer to cover the heat load is costly and generates major difficulties in design. A higher number of stages can reduce the heat load but will also raise the investment cost. The influence of increasing stage numbers on operating cost and capital investment of the HIDiC was evaluated by two HIDiC design cases, and the stage numbers or equivalently the heat loads were optimized to achieve the balance between the two kinds of cost.