Power-to-Gas(P2G) is the one of systems storing electricity. Using this system, load fluctuations due to utilizing renewable energy can be appropriately coped. In this system, surplus electricity produced from renewable source can be converted into hydrogen by water-electrolysis and produced hydrogen would be utilized to methane along with carbon dioxide. In this study, two hydrogenotrophic methangen that are applicable to biological methane production was isolated from sludge and the performance for methane production was evaluated in same condition. Minimal medium such as basic anaerobic medium was utilized for cell maintenance and methane evaluation. Carbon dioxide and hydrogen were supplied as a carbon and energy source at various ratio and rate. Produced methane and cell growth was analysed using GC-TCD and spectrophotometer by time course, respectively. Based on these results, methanogen suitable for P2G system could be selected.