The Danish green transition targets for 2030 aim to install 6 GW of Hydrogen (H2) production units, despite lacking a regulatory framework for grid connection, ancillary services, and H2 markets. In contrast, the 9 GW of wind and solar PV capacity were deployed over two decades, with regulatory adjustments made as their share in power generation grew. Today, both wind and solar PV follow the same grid connection standards. Until Q2 2024, electrolyzers were treated solely as consumers connected to distribution or transmission grids, without specific requirements for integration, control, or coordination at large scale. To enable upcoming tenders for GW-scale electrolyzer plants, Energinet released the first draft of grid connection requirements in Q2 2024, covering co-located overplanted facilities comprising renewable energy, storage, and electrolyzers. These regulations are expected to be in force by Q4 2024, facilitating the upcoming PtX tenders in 2025.Challenges for developers include the limited flexibility of existing products to adjust H2 production based on fluctuating renewable power supply and the lack of interoperability standards for electrolyzers. Reliable communication between control units is essential for safe and efficient plant operation. Moreover, “grid compliance by simulation” is required, however there are no standardized models for electrolyzer units/plants for grid integration studies. Some activities on this area were just started by IEA. These new facilities must provide new combined functionalities at plant level using the renewable generation, energy storage and H2 production units with a wide range of dynamic performance from tens of milliseconds to tens of minutes over different operational conditions. Moreover, these new hundreds of MW hybrid plants must ensure their proper operation but also the reliability and security of the entire Danish power supply.