A vanadium-redox-flow-battery (VRFB) model suitable for annual energy feasibility analyses of distributed storage implementation is presented in this paper. The validation of the proposed 6-kW/20-kWh VRFB semiempirical model, which takes into account auxiliary power consumption and operational aspects such as startup and standby behavior, is reported. The comparison between the simulation and the experimental results shows a good matching, quantified by the maximum root-mean-square deviation of the stack energy equal to 1.57% and 2.47% during charge and discharge, respectively. Moreover, the VRFB model is used in an application model of a residential building including a photovoltaic system and heat pump. Based on variation of control parameters, the energy efficiency for the proposed application has been maximized. Finally, a comparison with a scaled VRFB model (3 kW/10 kWh) is discussed with respect to the increase of the VRFB utilization and overall energy efficiency, confirming the effectiveness of the proposed model for distributed energy storage sizing and management in residential systems.