The balance between reflux ratio and number of plates becomes an economic concern, where a trade off has to be reached between the higher capital cost of the manufacture and installation of a larger column (more plates, lower reflux ratio), versus higher operating costs due to increased reboiler and condenser heat loads, and therefore increased steam and cooling water requirements, for a smaller column (fewer plates, increased reflux ratio). Figure 5.2 shows the variation of capital investment (fixed costs) and operating costs (steam and cooling water costs) with reflux ratio.