What is an on-site hydrogen generator?
An on-site hydrogen generator is an electrolyzer that produces hydrogen gas from water and electricity at the point of use, replacing delivered cylinders, tube trailers or bulk storage. Industrial and laboratory generators use proton exchange membrane (PEM) or alkaline electrolysis to deliver dry, high-purity hydrogen on demand.
For many facilities, the appeal is practical as much as economic. On-site generation eliminates cylinder changeouts and delivery schedules, reduces the amount of hydrogen stored on site and gives predictable supply for equipment that cannot tolerate interruptions, such as hydrogen-cooled generators.
How water electrolysis works
PEM electrolysis. Deionized water is fed to the anode side of a cell. Electric current splits water into oxygen, hydrogen ions (protons) and electrons. A solid polymer membrane allows only protons to pass to the cathode, where they recombine with electrons as hydrogen gas. Oxygen is vented, and the hydrogen is dried to a low dew point and delivered at pressure.
Alkaline electrolysis. Electrodes sit in a liquid potassium hydroxide solution. Hydroxide ions carry charge between electrodes, producing hydrogen at the cathode and oxygen at the anode. Alkaline technology is well established for large, steady production.
Because PEM systems can ramp quickly, kilowatt-scale generators follow demand automatically, producing only what the process uses. That load following is what allows many sites to reduce hydrogen storage.
| Supply option | How it arrives | Advantages | Drawbacks |
|---|---|---|---|
| High-pressure cylinders | Delivered and swapped | Low capital cost, flexible | Handling labor, delivery charges, supply interruptions |
| Tube trailers or bulk storage | Delivered in large volume | Suited to high demand | Large stored inventory, site safety planning, logistics |
| On-site PEM generator | Made from water and power | High purity, dry gas, load following, minimal storage | Capital cost, power and water utilities |
| On-site alkaline electrolyzer | Made from water and power | Low cost at large scale | Larger footprint, caustic electrolyte |
Common applications
- Power generation: makeup hydrogen for large hydrogen-cooled generators. Hydrogen’s low density reduces windage losses, and its high thermal conductivity removes heat efficiently. Nel cites installations including AEP’s Clinch River plant in Virginia.
- Metals and thermal processing: reducing atmospheres for annealing, sintering, brazing and metal additive manufacturing in plants across the Southeast.
- Semiconductor and electronics: high-purity process hydrogen.
- Laboratories: GC carrier gas and FID fuel gas for environmental, university and quality control labs.
- Green hydrogen projects: megawatt-scale electrolysis for industrial decarbonization, ammonia, steel and fuels.
Choosing the right hydrogen generator
Sizing starts with a realistic demand profile, not a nameplate estimate. Generator cooling makeup, furnace atmospheres and lab gas servers have very different peak-to-average ratios, and PEM load following changes how much storage you need. Purity, dew point and delivery pressure narrow the product family. Utilities and codes often determine installation cost, including power, deionized water, ventilation and NFPA 2 and NFPA 55 requirements. Finally, compare lifecycle cost and supply security against your current delivered gas contract.
Manufacturers we represent for hydrogen generation
Nel Hydrogen, formerly Proton OnSite, is one of the longest-running water electrolyzer manufacturers. Its Wallingford, Connecticut factory has built PEM hydrogen generators for about three decades and was expanded with an automated production line in 2024. Nel’s S, H and C Series generators cover laboratory and industrial point-of-use supply, from 0.27 to 30 Nm³/h. For large projects, the company offers containerized MC Series PEM systems, PSM Series stack platforms and A-Series and PA-Series alkaline electrolyzers. Nel’s management systems are certified to ISO 9001, ISO 14001 and ISO 45001.
Get local application support
Vaughn Associates helps utilities, manufacturers and labs define hydrogen demand, utilities and installation needs, and coordinates proposals with Nel. Visit engineering support, request a quote, or find your area manager on the territories page.
