An economic comparison is made between electrode configurations for flow redox battery applications: (i) the flow-through configuration (current parallel to the fluid flow) and (ii) the flow-by configuration (current perpendicular to the fluid flow). Steady-state computer models are developed for each electrode system. These models are used to predict current density, cell voltage, and power density over a complete cycle (charge and discharge). The economic comparison is made by optimizing each configuration with respect to an objective function appropriate for redox battery applications. Only the variable costs are considered. The results of the optimization show that the flowbby configuration is superior. The flow-through configuration not only yields a lower return on investment, but it is impractical due to a requirement of extremely low flow rates (Re < 0.001). Its failure is due to current flow (and ohmic potential drop) in the same direction as the fluid flow.