The membrane-aerated biofilm reactor (MABR) is a novel, energy-efficient technology that provides wastewater treatment by passively supplying dissolved oxygen directly to a biofilm, without the formation of bubbles. Significant energy savings may be obtained by using the MABR for wastewater treatment, as compared to the conventional activated sludge process. In this study, we used modeling and cost estimation, as well as a sensitivity analysis, to determine the potential energy and cost savings of the MABR. Results suggest that energy savings can exceed 85%. The savings in energy and costs are strongly affected by the following: MABR fluxes for COD removal, nitrification, and denitrification; membrane costs (impacted by membrane material, the cassette assembly, and specific surface area); mixing energy requirements; and the life cycle cost of membrane. Further research is needed to better quantify the above variables, as well as develop and test potentially scalable and retrofittable reactor configurations. If feasible, the MABR can allow for more sustainable and cost effective wastewater management.