Power to gas could get an important issue in future, permitting the valorisation of green electric excess energy by producing hydrogen, mixing it with natural gas (NG) and use the NG grid as temporary storage. NG grid stakeholders expect that blends up to 20% seem to be a realistic scenario. The knowledge of the explosion group for these hydrogen/NG (H2NG) mixtures is a necessary information for the choice of equipment and protective systems intended for the use in potentially explosive atmospheres of these mixtures. Therefore, we determined experimentally the minimum ignition current (MIC), the MIC ratios referenced on MIC of pure methane, corresponding to IEC 60079-20-1 standard. The results are compared to those obtained by maximum experimental safe gap (MESG), the second standardized method. The tested gas mixtures started from 2 vol.% volume admixture in methane rising in 2% steps up to 20 vol.% of hydrogen. The interpretation of these results could conduct to consider methane/hydrogen mixtures containing more than 14 vol.% of hydrogen as Group IIB gases.