Hybrid electrical energy storage (HEES) systems have the potential to result in considerable cost savings by reducing the electric bills of home users. This paper first presents grid-connected dual-bank HEES system design and management to maximize the electric bill savings for residential users, and subsequently provides a comprehensive sensitivity analysis of the economic feasibility of residential HEES systems. Specifically, the paper describes a daily management policy based on energy buffering strategy with one bank as the main storage bank and the other as the energy buffering bank, and then derive the global design of HEES specifications based on the daily management results. Simulation results prove the effectiveness of energy buffering strategy and show the proposed HEES system is capable of bringing in profits under current input variables. Finally, a detailed analysis is conducted to show how each input variable affects the final design of the proposed residential HEES system and the maximum annual profits it achieves. Together with the design and control mechanism, the proposed analysis provides potential customers with the comprehensive knowledge of how HEES systems can be deployed to achieve savings in their electric bills.