There are four main types of electrolysers (Alkaline, PEM, AEM, and SOEC) for converting water and electricity into hydrogen gas. Each option comes with its advantages, disadvantages, and optimal applications. The right electrolyser depends on your energy profile, usage patterns, siting limitations, and scalability plans.
What Is An Electrolyser?
An electrolyser is a device that splits water (H₂O) into hydrogen (H₂) and oxygen (O₂) using electricity. This process is called electrolysis. When powered by renewable energy, electrolysis becomes a zero-emission method for generating hydrogen gas.
While the basic principle is the same across all types of hydrogen electrolysers, the electrolyte, membrane material, temperature and pressure flexibility, system architecture, and operating costs vary. These differences shape how each technology performs in real-world conditions. Whether you’re deploying hydrogen in industrial energy systems, microgrid, or long-duration energy storage, the type of electrolyser can determine the success of your project. Let’s examine the differences and use cases of the four most popular electrolyser types in the hydrogen landscape.
The 4 Main Types of Electrolysers
1. Alkaline Electrolysers
Alkaline electrolysers have been used in commercial applications for decades. They use a liquid alkaline solution, typically potassium hydroxide (KOH) or sodium hydroxide (NaOH), as the electrolyte. A diaphragm separates the hydrogen and oxygen gases, preventing them from mixing while allowing ion flow between the electrodes.
This method keeps system costs low, utilizes durable components, and offers long operational lifespans. However, alkaline electrolysers have a slower dynamic response, making them less suitable for pairing with variable renewable energy sources. They also tend to be bulkier and operate at lower current densities than other electrolysers.
Use Case: Alkaline electrolyser systems are best suited for large-scale hydrogen production, particularly in industrial facilities with consistent power input and applications where space is not a limiting factor.
2. Proton Exchange Membrane (PEM) Electrolysers
PEM electrolysers use a solid polymer membrane as the electrolyte, which conducts protons while blocking gases to ensure high-purity hydrogen output. Operating at relatively low temperatures, these systems are known for their fast response times and ability to handle power fluctuations.
Their compact design makes them ideal for installations with space constraints, and they can produce hydrogen at high pressures, reducing the need for additional compression. However, PEM electrolysers rely on costly noble metal catalysts, such as platinum and iridium. These catalysts contribute to higher operating costs, on top of high upfront costs. The membranes also have limited durability under certain conditions.
Use Case: PEM systems are well-suited for high-purity applications, such as fuel cells and transportation. They can also work well when integrating with renewable energy for on-site hydrogen production.
3. Anion Exchange Membrane (AEM) Electrolysers
AEM electrolysers, or Anion Exchange Membrane electrolysers, blend the best features of alkaline and PEM technologies. They use a solid anion-exchange membrane and rely on inexpensive, non-noble metal catalysts to reduce system costs while approaching PEM-like efficiency. Operating at relatively low temperatures, AEM electrolysers aim to offer a balance between performance and affordability.
Their key advantages include the elimination of costly noble metals, the flexibility for intermittent power, and suitability for compact systems. They are a strong fit for decentralized hydrogen production, cost-sensitive projects, and emerging markets or pilot programs. Power to Hydrogen specializes in this technology, working to advance AEM systems as a practical solution for distributed hydrogen generation.
Use Case: AEM systems are an excellent choice for modular hydrogen systems, small-to-medium projects, on-site production with limited maintenance staff, and microgrid applications. Contact us today for a free consultation to learn if Power To Hydrogen's AEM electrolysers are right for your project.
4. Solid Oxide Electrolysers (SOEC)
Solid Oxide Electrolysis Cells (SOECs) operate at extremely high temperatures, typically between 600°C and 1000°C, and use a solid ceramic electrolyte. These high temperatures make them highly efficient because they use heat to reduce electricity requirements.
Industrial facilities producing significant heat, such as steel mills, benefit from SOECs. These electrolysers can utilize waste heat from manufacturing processes to generate hydrogen. However, the high operating temperatures also present challenges: they strain materials, slow down start-up and shutdown processes, and currently limit widespread commercial deployment.
Use Case: SOECs are used almost exclusively in large-scale hydrogen production, particularly in industrial settings where waste heat is available.
Comparison Table Of Different Types of Electrolysers
Choosing the Right Electrolyser for Your Application
With multiple technologies available, selecting the right electrolyser means balancing several factors.
- Space Constraints: PEM or AEM electrolysers offer compact designs, making them the ideal choice for applications with limited footprints.
- Hydrogen Purity: PEM and AEM electrolysers produce very-high purity hydrogen, which requires minimal post-processing before use.
- Budget: Alkaline systems are typically the most affordable up front. PEM and SOEC may have higher initial costs but lower operational expenses. AEM offers the best balance of CAPEX and OPEX, with increased savings potential as the technology scales and matures.
- Hydrogen Storage: For pressurized hydrogen needs, AEM and PEM systems are the best options. Both operate efficiently up to 30 bar, reducing the need for post-compression. Alkaline systems typically produce gas at low pressures, and SOECs require external compression systems.
- Energy Source Compatibility: PEM electrolysers are well-suited for intermittent and renewable energy, due to their fast start-up and dynamic response capabilities. Alkaline and SOEC perform best with consistent energy input.
Choosing the wrong electrolyser type could lead to energy waste, underperformance, or excessive maintenance. At Power to Hydrogen, we guide clients through these considerations, ensuring they select the electrolyser type that matches their specific project needs.
The Role of Electrolysers in Hydrogen's Future
As countries and industries move toward decarbonization, electrolyser investments are increasing and the technology is evolving quickly. Governments are backing hydrogen production to help hit emissions targets, and aim to bring hydrogen costs below $1 per kilogram. AEM electrolyser technology is the strongest candidate to help meet these goals. While PEM and alkaline are already established, they carry compromises in either cost or flexibility. SOEC may prove valuable for niche high-heat use cases. But AEM is built for reliable, cost-effective, and flexible hydrogen.
Power to Hydrogen’s Hybrid AEM Electrolysers
If you want PEM’s agility without its cost profile and alkaline’s economics without its operational drag, Power to Hydrogen’s hybrid AEM electrolysers are the solution. It’s engineered for real grids, real sites, and real budgets. Here are some of the reasons that engineers are choosing to work with Power To Hydrogen for hydrogen electrolysis:
- Fast, stable dynamics: Tracks intermittent solar and wind profiles with quick start/stop.
- Lower critical materials risk: Avoids heavy reliance on scarce PGM catalysts, helping de-risk both cost and supply chain.
- Simpler operations: No concentrated KOH loops like traditional alkaline.
- Compact footprint: Modular skids sized for space-constrained sites, microgrids, and behind-the-meter projects.
If you’re planning a pilot, repower, or multi-MW build, P2H2’s hybrid AEM gives you room to engineer, not just accommodate trade-offs. Tell us your load profile, water specs, and target purity, and we’ll map a stack and skid package to your site constraints and cost model.
Get Expert Advice on the Right Electrolyser for Your Project
Every hydrogen project is different. Whether you’re building a small-scale renewable energy system or planning a utility-scale deployment, selecting the correct type of electrolyser is a crucial decision that impacts efficiency, cost, and scalability. Contact us today to discover how our electrolysers can help you achieve your hydrogen goals. Our experts are happy to discuss your project and begin your journey toward sustainable hydrogen production.
