This paper investigates the cost reduction opportunity of lower CO2 capture ratios (CCR) on membrane-based CO2 capture. A numerical model based on the attainable region approach is used to optimise and assess the cost of membrane-based processes for CO2 capture from post-combustion flue gases containing 10-35% CO2, analysing five membranes and CO2 capture ratios from 50 to 90%. Overall, these cost evaluations demonstrate that membrane-based post-combustion CO2 capture can significantly benefit from lower CCRs (up to 55% reduction in CO2 avoidance cost for a flue gas containing 35% CO2). Considering lower CCRs could therefore enable early deployment of CCS despite low carbon emission cost, however the evaluations show that the optimal CCR and corresponding cost reduction potential shall be assessed considering the whole chain characteristics (CO2 content in the flue gas, impurities, membrane module properties, CO2 transport system, etc.). (C) 2017 Elsevier B.V. All rights reserved.