Alcohols are important solvents with a variety of applications. This paper describes cost estimations of pervaporation (PV) and vapor permeation (VP) membrane separation systems for ethanol-water mixtures. Experiments using a homogeneous cellulose membrane are performed at higher ethanol feed concentration (above 90 wt%) , since conventional distillation is economical at lower concentration. The fluxes observed are smaller, and the selectivities are larger in VP compared to PV. However, the differences in PV and VP decrease with increasing ethanol feed concentration. Simulated calculations are carried out for the estimation of membrane area under three operational conditions for a commercial-scale plant, based on these experimental data. As a result, it has been clarified that membrane area steeply increases at higher concentrations. The low flux involved demands a larger membrane area in VP compared to PV. A conceptual design of the membrane separation system is presented, and the costs of membrane module and other main components are estimated. As a result of this economic assessment, it is clarified that capital cost is significantly affected by the membrane area, and that cost is lower in PV compared to VP over a wide scare of plants. But contradictory results are obtained from other researchers＇ data using the GFT membrane. The economics of membrane separation systems. strongly depend on separation characteristics of the membrane and the range of concentration. Next, the authors discuss the selection of an applicable membrane from various PV data showing "trade-off" relations between a and flux. It is clarified that high flux is a very important condition, rather than high selectivity for industrial applications.