The idea behind Power-to-Gas (P2G) is to help provide flexibility to renewable energy sources such as wind farms with intermittent nature. Additionally, hydrogen shows a great potential to help decarbonize several industries and its demand is expected to rise massively. Several studies for the technical and economic feasibility of P2G show possibilities of positive business cases far offshore. Platforms, owing to their minimal construction time and lower environmental impact provide an interesting choice of hub structure to equip electrolyser systems. However, gaps exist in the understanding of the costs of such a P2G offshore platform, driving factors, equipment involved, capacity limit and the feasible substructures to support such a facility. The main goal of this thesis is to increase the knowledge of system integration of offshore wind and electrolysers, estimate the scale and size of such a platform involving stacks, balance of plant, power electronics, auxiliary systems and the substructure supporting the topsides. In line with this goal, the study details the system design and parameters, estimates costs of each of the components involved and finally builds a cost model to understand the driving factors for an economical design of such a facility offshore.