High energy density flow batteries provide a potential solution to large-scale electrical energy storage needs. The high energy density fluid electrodes for such devices will typically have non-Newtonian rheology, especially when formulated as suspensions which increase electrical conductivity, energy density, or both [M. Duduta et al., Adv. Energy Mater., 1, 511 (2011); Z. Li et al., Phys. Chem. Chem. Phys., 15, 15833 (2013)]. A computational model that simulates electrochemical kinetics and flow is used to quantify coulombic and energetic efficiency under various flow conditions, taking as examples flow electrodes that contain suspensions of active materials (LiFePO4, LiCoO2) or conductive networks in redox solution (vanadium redox). Intermittent flow pulses of controlled volume and duration are found to incur less than half the electrochemical losses of continuous pumping. Increased slip and yield stress are shown to increase flow uniformity, energetic efficiency, and discharge energy. From these findings a general strategy is derived for the maximization of efficiency in energy-dense flow batteries applicable to arbitrary cell designs, suspension types, and operating conditions. (C) 2014 The Electrochemical Society. All rights reserved.