To fight the threat of global warming, nations worldwide are currently in the transition towards a renewable-powered energy system. One of the main technologies represented in a renewable-powered energy system is wind energy. Rapid developments in the offshore wind sector caused the rise of offshore wind farms in the North Sea and more wind farms are expected for the years to come. As this renewable-powered energy system will be heavily dependent on the availability of wind and solar energy, great challenges will arise to the security of supply in the energy system. To tackle this challenge, nine countries surrounding the North Sea (called NSEC) cooperate on researching a cost-efficient energy system design which enables the large-scale deployment of wind and solar energy. One aspect that hasn’t been researched for the NSEC so far is the potential of hydrogen for this energy system. Hydrogen can play an important role in the future renewable energy system as fuel and feedstock for different sectors and as energy carrier that allows for seasonal storage. The question of what energy system design choices bring the most cost-efficiency for the NSEC, considering the hydrogen and electricity demand in 2050, will be researched. For this research, results have been based on optimizing the future energy system in the simulation modelling program Powerfys. This model optimizes power plant utilization while taking the constraints assigned to the power plants and to the energy system infrastructure into account. Powerfys operates on a rolling planning on the intra-day and the day-ahead market. The model consists of 50 nodes, divided over 9 countries and the North Sea. By simulating scenarios focused on either renewable energy capacity expansions or transmission infrastructure design, different levels of cost-efficiency are determined. These outcomes will allow to answer the research question. This research shows that a cost-efficient energy system for both electricity and hydrogen in the NSEC can exist with the current planned electricity and natural gas transmission grid for 2050, assuming a fully retrofitted natural gas grid, exclusively utilized for hydrogen transmission. What this study does show is that extensive amounts of offshore wind (285 GW) and other renewables (245 GW of onshore wind and 434 GW of PV) must be deployed, to meet the expected electricity and hydrogen demand of 2050. For offshore wind this means that not only the potential of bottom-fixed wind turbines should be accounted for, but also the potential of the novel technology of floating wind turbines must be considered. On top of that, this study shows that only 4 to 5% of all hydrogen demand must be imported from outside NSEC. Even without the imports of any hydrogen, meeting full electricity and hydrogen demand would be technically possible, but this would lead to higher energy system costs for the deployment of higher capacities of renewables and the storage for hydrogen in salt caverns. Though, the sensitivity analysis shows that hydrogen imports can increase significantly when price levels related to hydrogen (import-, electrolyser- or hydrogen storage prices) will turn out different in 2050 than currently expected. Nevertheless, this research also shows that such a significant increase in hydrogen imports will not lead to remarkable deviations in the overall energy system design or the energy system costs.