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Electrolyser grid connection: problems and solutions


Large scale, grid connected electrolysers must not be a source of instability and must be able to withstand sudden voltage or frequency changes without damage. What does that mean for grid operators, technology providers, and plant operators?


Sven Schumann Head of Primary Electric/Water Electrolysis and Juergen Heller Senior Expert Product Lifecycle Management, Sustainable Energy Systems at Siemens Energy


For decades, conventional power plants such as coal and nuclear units provided more than electricity. Their heavy rotating generators stabilised grid frequency at 50 or 60 Hz, acting as shock absorbers during sudden changes in demand or supply. As these plants are phased out in favour of inverter-based renewables such as wind and solar, that natural inertia disappears, making frequency control harder and grid stability more fragile.


Electrolysers add another dimension to this challenge. They are central to the energy transition, converting electricity and water into green hydrogen for sectors where direct electrification is not feasible. In the EU alone, 40 GW of electrolyser capacity are planned, meaning not only more plants, but much larger ones. And they are not alone – other emerging large-scale consumers such as data centres and grid-scale battery storage will also need to be integrated into a system already stressed by the rise of variable renewables and the decline of conventional, controllable plants with their stabilising functions. A single industrial-scale electrolysis unit can draw hundreds of megawatts, comparable to the electricity demand of a city with 350 000 residents. Unlike a city, which has thousands of connection points, an electrolyser connects to the grid at a single node. If something goes wrong at that point, both grid stability and stable plant operation are at risk.


Integrating these large consumers with their electrochemical processes into the grid requires careful planning. Operators, manufacturers,


and plant owners must work together to ensure that electrolysers do not destabilise the system and that they can withstand sudden voltage or frequency changes without damage.


Grid operator requirements: from passive load to active support Europe’s grid is under increasing stress as conventional plants with stabilising inertia disappear and renewables dominate. In this environment, connecting multi-megawatt electrolysers adds significant complexity. To maintain stability, grid operators rely on fast- reacting systems and strict technical rules that define how connected equipment must perform to keep the grid safe and reliable, so-called grid codes. The expectation is clear: electrolysers must move beyond passive consumption to active support of the grid.


European regulations, driven by the revision of the Demand Connection Code, are tightening. Some requirements, such as voltage and frequency bands, harmonic limits, and baseline reactive power control are already established. Others, like advanced dynamic functions, will become mandatory in the coming years. In addition to EU-wide regulations, many countries are developing their own, usually stricter, requirements for electrolyser grid connection, adding further complexity to project planning. Developers must design for compliance today and anticipate stricter rules for the projects of tomorrow.


Key functions include: fault ride through (FRT), which keeps plants connected during short


voltage spikes and dips and restores power quickly; limited frequency sensitive mode (LFSM), where consumption adjusts with frequency deviations; and, possibly in the future, power oscillation damping, adding fast modulation to prevent instability. These active power responses directly affect hydrogen output and cannot be treated as secondary.


Reactive power obligations are equally demanding. Plants must stabilise voltage through fixed power factors or dynamic Q(U) curves and inject reactive current during faults – often within milliseconds – to prevent cascading failures. Meeting these requirements calls for plant-wide design, precise control systems, and validated models that balance grid support with safe, efficient hydrogen production.


PEM stacks at the Siemens Energy electrolyser factory, Berlin. Photo: Siemens Energy 16 | July/August 2026 | www.modernpowersystems.com


The manufacturer’s perspective: technology that responds fast Electrolyser technology is evolving to meet these demands. Modern systems, especially proton exchange membrane (PEM) electrolysers, can adjust power intake within seconds, making them suitable for frequency control. This dynamic behaviour allows them to deliver: frequency containment reserve (FCR), which reacts within seconds to stop frequency deviations; automatic frequency restoration reserve (aFRR), which restores balance within minutes using automated signals; and manual frequency restoration reserve (mFRR), which provides backup through manual activation over a longer timeframe, turning a large consumer into a flexible grid resource. New grid code requirements demand even faster reaction times. This has an impact on the whole electrolyser plant. Manufacturers must design entire plants, including electrical systems, automation, and control software, to respond quickly and safely especially to grid events. For example, active power adjustments directly affect hydrogen production and depend on how the DC current is managed. Reactive power support, such as voltage control, adds another layer of complexity. Safety limits also matter. Large-scale electrolysers operate under strict constraints to prevent dangerous gas mixing, such as hydrogen crossing into the oxygen side. These limits define the lowest operating range and influence how far the plant can ramp down during grid disturbances. Balancing flexibility with safety is a key design challenge for manufacturers.


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