In 2020, the European Commission launched a hydrogen strategy for a climate-neutral Europe, setting out the conditions and actions for mainstreaming clean hydrogen, along with targets for installing renewable hydrogen electrolysers by 2024 and 2030. Blending hydrogen alongside other gases into the existing gas grid is considered a possible interim first step towards decarbonising natural gas. In the present analysis we modelled electrolytic hydrogen generation as a process connecting two separate energy systems (power and gas). The analysis is based on a projection of the European power and gas systems to 2030, based on the EUCO3232.5 scenario. Multiple market configurations were introduced in order to assess the interplay between diverse market arrangements in the power market and the constraints imposed by the upper bound on hydrogen production due to quality requirements set by gas system operators. The study identifies the maximum electrolyser capacity that could be integrated in the power and gas systems, the impact on greenhouse gas emissions, and the level of price support that may be required for a broad range of electrolyser configurations. The study further attempts to shed some light on the potential side effects of having non-harmonised H2 blending thresholds between neighbouring member states.