Sizing a residential battery bank depends on whether the objective is partial backup during brief power outages or complete self-consumption independence. For essential backup covering refrigerators, lights, Wi-Fi, and medical devices during short outages, a 10kWh to 15kWh capacity battery is usually sufficient. For whole-home backup encompassing high-draw appliances like central air conditioning systems and electric water heaters, households typically require 30kWh or more of aggregated storage capacity.