This part of IEC 62282-8, which is an international standard, addresses Solid Oxide Cell (SOC) cell/stack assembly unit(s). It provides for testing systems, instruments and measuring methods to test the performance of SOC cell/stack assembly units for energy storage purposes. It assesses performance in fuel cell mode, in electrolysis mode and/or in reversible, or regenerative, operation. 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 solid oxide cell that alternates between fuel cell mode and electrolysis mode reversible . This international standard is not applicable to small button cells that are designed for SOC material testing and provide no practical means of reactant utilization measurement, or to single-chamber SOC. This Standard is not intended to be applied to fuel cell/stack assembly units for power generation purposes only, since this is covered in IEC Technical Specification 62282-7-2. Therefore, test methods are not included in this document that are applicable to fuel cell mode only and that are already described in IEC Technical Specification 62282-7-2. This international standard is to be used for data exchanges in commercial transactions between cell/stack manufacturers and system developers or for acquiring data on a cell or stack in order to estimate the performance of a system based on it. Users of this international standard may selectively execute test items suitable for their purposes from those described in this international standard. Users may also substitute selected test methods of this Standard 62282-8-101 with equivalent test methods of IEC Technical Specification 62282-7-2 for SOC operation in fuel cell mode only.