Electrical energy is a high quality form of energy that can be easily converted to other forms of energy with high efficiency and, even more importantly, it can be used to control lower grades of energy quality with ease. However, building a cost-effective electrical energy storage (EES) system is a challenging task despite steady advances in the design and manufacturing of EES elements including various battery and supercapacitor technologies. As of today, no single type of EES element fulfills high energy density, high power delivery capacity, low cost per unit of storage, long cycle life, low leakage, and so on at the same time. Unlike conventional EES systems, we introduce a HEES (hybrid EES) system comprising heterogeneous EES elements. Our proposed HEES system builds on the concepts of computer memory system architecture and management in order to achieve the attributes of an ideal EES system through appropriate allocation and organization of various types of EES elements. We also introduce a HEES design considerations which should be taken into account to optimize the amortized cost for the system, including the initial cost (cost per capacity), the operating cost (efficiency), the maintenance cost (cycle life and disposal cost), and so forth.