This document specifies the performance test methods of the power-to-methane systems based on solid oxide cells (SOCs). Water, CO2, and electricity are supplied to the system to produce methane and oxygen. This document is not intended to be applied to SOFC cell/stack assembly units for power generation purposes only, since this is covered in IEC TS 62282-7-2. It is also noted that test methods for SOC cell/stack including reversible operation (without any methanation reactor) are already described in IEC 62282-8-101. Users can substitute selected test methods of this standard with equivalent test methods of IEC 62282-8-101 (SOEC to produce H2 only as well as SOFC operation mode and reversible mode) and IEC TS 62282-7-2 (SOFC mode only). This standard covers two types of processes as shown in Figure 1: " Case 1: Steam and CO2 are introduced into SOC (co-electrolysis process), and the product gas (mainly, H2 + CO) is supplied to a methanation reactor (catalytic reactor); " Case 2: Steam is introduced into SOC to generate H2, which is supplied into a methanation reactor with CO2. Besides two cases, the methanation catalyst can be integrated within the SOC, but it is not in the scope of the present edition of this standard. This document provides for testing systems, instruments and measuring methods to test the performance of SOC cell/stack assembly units and methanation reactor for energy conversion purposes. To produce CH4 from water and CO2, SOC is operated in electrolysis mode (solid oxide electrolysis cell, SOEC). SOC can be operated in fuel cell mode (solid oxide fuel cell, SOFC) and/or in reversible operation mode. In the present edition of this standard, the system is considered not to have components which store electricity, media, or heat. This document is intended to be used for data exchanges in commercial transactions between the system manufacturers and customers. Users of this document can selectively execute test items suitable for their purposes from those described in this document.