The integration of water electrolyzers into the electrical energy system is a key component of the energy transition. In the past, electrolyzers were being connected to the grid solely as consumers. However, large-scale electrolysis units with connected loads exceeding several hundred megawatts have a considerable impact on grid stability. Given the decreasing number of connected thermal power plants (nuclear, gas, and coal), the high total installed capacity planned, and the slow progress in expanding transmission infrastructure, grid code compliance with more demanding requirements for electrolyzers will become increasingly important. Transmission system operators (TSOs) impose strict requirements on the grid compatibility of electrolyzers. With appropriate system design, the next generation of electrolyzers can not only produce hydrogen but also contribute significantly to the stability of the electrical grid and, consequently, to the security of supply.