The rapid transformation of power systems is accelerating the need for new forms of flexibility. While traditional sources of flexibility—such as thermal plants and large‑scale storage—remain important, attention is increasingly shifting toward large electrical loads capable of providing fast, controllable demand. Industrial‑scale electrolysers are among these emerging flexible assets. Unlike traditional passive loads, converter‑dominated loads interact with the grid across a wide frequency range, with behaviour shaped by control loops, DC‑link dynamics, and internal process characteristics. These interactions can give rise to adverse effects such as harmonic amplification and small‑signal instabilities, particularly in weak grids. As the penetration of such loads increases, understanding their frequency‑dependent behavior becomes essential for stable system operation. This paper addresses this challenge by developing a comprehensive analytical impedance model for large electrolysers. The analytical formulation provides a transparent and computationally efficient tool for small‑signal stability assessment.