||The increasing interest in electrolytic hydrogen production using renewable electricity sources will require to adapt power systems to new electrical loads for hydrogen production and supply chains. Such high loads would impact the long-term planning and operation of power systems, as they need to balance the variability of renewable generation sources with electricity demand. This stresses the importance of characterizing the impact of incorporating hydrogen supply chains into power systems and planning accordingly. This study proposes a methodological framework to assess the integration and development of a national power system with electrolytic hydrogen production and supply chain. The framework is based on the well-known optimization tool for energy systems planning, Open Source Energy Modeling System (OSeMOSYS). For a detailed representation, a module was developed where demand side technologies � such as those associated to hydrogen supply chains � can provide operating reserves. As a case study, the integration of the Chilean power system with a hydrogen supply chain for exporting hydrogen between 2018 and 2050 was modeled. Among other findings, results indicate that an on-grid hydrogen supply chain would be more cost-effective than an off-grid one. However, the new electrical loads originated from such hydrogen supply chain would require additional generation capacity � primarily photovoltaic. Other generation capacities such as concentrated solar power, wind, and storage would experience significant variations in their investment requirements, compared to the off-grid hydrogen supply chain scenario. The study revealed that the coordinated operation of electrolyzers is crucial to the operational flexibility of the new electrical system.