This part of IEC 62282 defines the evaluation methods of typical performances for electric energy storage systems using hydrogen. This is applicable to the systems which use electrochemical reaction devices for both power charge and discharge. The conceptual configurations of the electric energy storage systems using hydrogen are shown in Figure 1 and Figure 2. Figure 1 shows the system independently equipped with an electrolyzer module and a fuel cell module. Figure 2 shows the system equipped with a reversible cell module. There are an electrolyzer, a hydrogen storage and a fuel cell, or a reversible cell and a hydrogen storage as indispensable components, and a battery, an oxygen storage, a heat management system, a water management system and an overall management system as optional components. The performance measurement is executed in the area surrounded by the outside thick solid line square (system boundary). Note: In the context of this international standard, the term “reversible” does not refer to the thermodynamic meaning of an ideal process. It is common practice in the fuel cell community to call the operation mode of a cell that alternates between fuel cell mode and electrolysis mode “reversible”. A typical targeting application of the electric energy storage systems using hydrogen is in the class of energy intensive electric energy storage. The systems are recognized as critically useful for the relatively long-term power storage operation, such as efficient storage and supply of the renewable power derived electric energy and grid stabilization.