In a membrane separation unit with moderate permselectivity values, in order to recover products in high amount and high purity, it is important and sometimes necessary to cascade membrane units together in stages. The proper selection of such a cascade arrangement and operating parameters, to minimize capital cost and energy consumption is an important problem. The principal objective is to minimize the energy consumption in a cascade, but not use more than a few stages to keep capital costs low. Currently, all such design is done through innovative optimization technology, and there is no complete fundamental theoretical framework that guides the design. An important step in order to make membranes competitive is to develop a methodology to robustly design low energy consumption membrane separation schemes. Our approach focuses on developing a simple framework that may be easily automated by any user and guide them through the design of the economically optimal membrane cascades. In this work we present our analysis and limitations of several existing membrane cascade design strategies. Through our analysis we have also identified some novel, easy to implement and intuitive design ideas that could lead to high energy savings while using only a few stages in the membrane cascade.