The usable output of an electrolyzer is the hydrogen it delivers under an agreed set of conditions—not just a headline flow or electrical rating.
Pressure, purity, dew point, auxiliaries, operating hours and the delivery point change the equipment you need. Two offers can name the same production rate while one excludes water treatment, rectification, cooling or drying. This guide gives engineers and buyers a common basis for comparing them.
The short answer: write a one-page hydrogen duty and battery-limit statement first. Compare technology, system scope and tested performance against that statement; only then rank price and schedule.
1. Is PEM the right route for the project?
PEM water electrolysis is often considered when footprint or variable-power operation matters. That does not mean it is automatically the lowest-cost or most durable answer for every site. A stable, continuous duty may lead the project team to compare alkaline systems; a heat-integrated process may raise different technology options. Keep the comparison at the same hydrogen delivery point and operating profile.
Match the technology to the actual operating pattern
A project that follows variable renewable power is different from one that runs steadily with grid electricity. For the first, ask how the proposed package handles starts, ramps, standby, low-load operation and shutdowns—not merely whether the stack can move quickly in a test. For the second, compare energy use, service strategy, equipment scope and site utilities at the expected continuous load. The technology decision belongs to the whole project, not to a headline stack response time.
Delivery pressure can also move equipment across the battery limit. If the user needs hydrogen at a higher pressure than the electrolyzer's delivered gas, the compression and storage route must be included in the project comparison. The same applies to drying, purification and analysis. A compact electrolyzer that leaves those functions to the EPC is not necessarily a smaller total installation.
Separate the buyer's task from a technology debate
Some readers already have a PEM requirement in a project specification. They do not need a long comparison of every electrolysis chemistry before they can evaluate a supplier. Others are still selecting a technology and need a common duty basis first. In either case, document the reason PEM is being considered—such as operating profile, footprint or integration constraints—then move to a system-level quotation. The rest of this guide assumes the purchase is for a PEM-based hydrogen supply and concentrates on what must be defined to buy it well.
HELE's PEM system business can support an application-specific review. A final configuration must still be matched to the project and supported by current model documents; a product-family name is not a performance guarantee.
2. What hydrogen duty should suppliers quote?
Start at the flange or sampling point where the buyer will accept the gas. State normal, minimum and peak hydrogen flow, annual demand and operating hours. Define whether volume is quoted at normal, standard or another reference condition. Then state pressure, purity, dew point and any impurity limits at that same point.
| Buyer input | Why it changes the system | What the offer must state |
|---|---|---|
| Time-based power and production profile | Starts, ramps, curtailment, standby and low-load operation affect stack and control duty. | Permitted operating envelope, turndown, controls and excluded conditions. |
| Gas delivery specification | Wet gas leaving a separator differs from conditioned gas after a dryer. | Guarantee and test location, included gas treatment and analytical method. |
| Water source and cooling | Actual source-water chemistry and available heat rejection shape the BoP. | Required inlet quality, treatment scope, cooling demand and monitoring points. |
| Site electrical supply | Power conversion and auxiliaries change the AC boundary and energy calculation. | Included rectifier/transformer, input quality, auxiliary loads and metering point. |
Make a time-based demand picture, not one rated-flow number
A plant's average demand, peak demand and annual total can point to different equipment arrangements. A short peak may be served differently from a continuous peak, depending on storage, turndown and the customer's tolerance for interrupted production. Show when hydrogen is used, how quickly the demand changes and how many hours each operating mode lasts. The supplier can then explain whether the package is sized for the peak, paired with storage, or constrained by a minimum stable load.
If renewable electricity is involved, give the power profile or at least the expected periods of curtailment, start-stop frequency and import limits. “Powered by solar” does not define a duty cycle. The U.S. DOE notes that durability assessment must consider dynamic operation and on-off cycling when the application requires them; its PEM targets are technology-development context, not a promise by any named supplier.
State what quality means at the delivery point
“Hydrogen purity” can hide several different requirements. The customer may care about total purity, water content, oxygen, nitrogen or application-specific contaminants. A downstream fuel cell, laboratory instrument or industrial process may each set a different acceptance point. State the end use and the applicable gas specification rather than assuming that a single percentage answers every quality question.
For each guarantee, identify the sampling point and operating condition. Is it wet gas after separation, conditioned gas after a dryer, or gas after external purification? What happens during startup or off-spec operation? If the conditioning equipment is supplied by another party, the electrolyzer vendor cannot alone guarantee the final quality at the user's connection.
Treat utilities as design inputs
Water is both a reactant and a system utility. The RFQ should include source-water analysis, the proposed treatment route and the quality required at the system inlet. Cooling supply temperature and available heat rejection matter because an assumed cooling-water service may not exist at the site. Electrical input voltage, frequency, available capacity and grid-quality constraints shape the rectifier and auxiliaries. Ask each bidder to list the inlet specification it needs and the remedy if the site cannot meet it.
Where data is missing, keep it as an open item in the RFQ. A supplier can then list an assumption and its price or design effect. That is more useful than silently inserting a brochure's “typical” utility value.
3. Are you buying a stack, a skid or a complete package?
The stack splits water electrochemically. The system around it prepares water and power, controls temperature and pressure, separates and conditions gases, and responds to abnormal conditions. These are different purchase boundaries.
| Scope item | Question for the supplier | Typical gap if left unstated |
|---|---|---|
| Stack and local module | Which build revision, electrical/fluid interfaces, leak tests and operating limits are supplied? | A stack test is mistaken for a complete-system test. |
| Power, water and thermal BoP | Are rectifier, water treatment, circulation, cooling and their controls included? | Auxiliary cost and energy are missing from the comparison. |
| Hydrogen treatment and delivery | Where are drying, analysis, pressure regulation and off-spec routing included? | Purity or pressure is quoted at the wrong location. |
| Site and EPC work | Who provides foundations, ventilation, piping, permits, installation and commissioning? | The lowest equipment quote leaves essential project work unfunded. |
What the purchase names can conceal
A stack-only buyer usually owns the surrounding power conversion, fluid circuits, controls, gas handling and system certification route. A skid may include some of those functions but stop at specified nozzles and electrical terminals. “Containerized” describes packaging; it does not tell you whether water treatment, compression, ventilation, fire or gas detection, foundations or site wiring are included. “Turnkey” is useful only when the seller lists the delivered assets, installation work and performance boundary in writing.
The minimum comparison is an equipment list plus a battery-limit drawing. For each connection, write the process medium, pressure or flow range, required quality, electrical rating, communication protocol, owner and acceptance point. A package can be mechanically complete yet not fit the site's power, water or downstream gas system.
Make the responsibility matrix part of the technical offer
| Interface | Typical decision to settle | Who must be named? |
|---|---|---|
| Feedwater | Source-water treatment, inlet quality, storage and monitoring. | Supplier, EPC or owner for each stage. |
| Electrical | Transformer, rectifier, protection, metering and grid connection. | Equipment supplier and electrical contractor. |
| Cooling | Available temperature, flow, heat rejection and backup response. | Supplier and site-utility owner. |
| Hydrogen/oxygen outlet | Gas treatment, safe venting, analysis, compression and piping. | Supplier, EPC and downstream user. |
| Controls and safety | Interlocks, emergency-stop interfaces, communications and alarm ownership. | Package integrator and site safety authority. |
HELE's PEM systems page shows the product direction, including multiple series. These names help start a conversation; they are not a current model-by-model availability or guaranteed-capacity table. Ask HELE to identify the configuration being quoted and mark every item included, optional, excluded or customer-supplied. A stack-only inquiry should be evaluated on its own interfaces and tests rather than inheriting a complete-system performance statement.
4. Which performance figures can be compared?
Compare hydrogen output, energy use and availability only when test conditions match. Stack DC consumption and complete-system AC consumption are not the same number. Likewise, a short stabilized test at rated load does not describe annual operation under a variable-power profile.
- For output: agree gas reference condition, measurement method, test duration and delivery point.
- For energy: identify stack DC, rectifier input or complete-system AC boundary, including auxiliaries.
- For quality: record pressure, purity, dew point, sampling location, analytical method and treatment of off-spec gas.
- For durability: define operating profile, beginning-of-life point, degradation metric and end-of-life threshold.
Do not compare different energy boundaries
A stack measurement starts at the stack's electrical terminals. A complete-system figure may include conversion losses, pumps, cooling, controls, water treatment and gas conditioning—or may omit some of them. Ask for a diagram of the meter locations, the auxiliaries counted and the hydrogen measurement point. The unit matters too: an energy figure stated per mass of hydrogen cannot simply be placed beside one stated per volume without the gas reference condition and conversion basis.
The operating point matters as much as the boundary. A package may be efficient at its rated point but spend much of the year at part load or standby. Request the proposed performance envelope over the loads the project will actually use, not only the best brochure point. If the buyer's power profile is uncertain, compare scenarios with the same assumptions rather than treating one supplier's forecast as measured annual performance.
Know what a guarantee and a test can demonstrate
| Statement in an offer | Question that makes it comparable |
|---|---|
| Rated hydrogen output | At which ambient, water, electrical and pressure conditions, for how long, and at which outlet? |
| Specific energy consumption | Stack DC or complete-system AC; which auxiliaries and gas reference condition are included? |
| Gas purity and dew point | Which sampling location, analytical method, load and stabilization period? |
| Availability or lifetime | What period, operating duty, exclusions, maintenance allowance and failure definition apply? |
A supplier should connect each claimed value to the model, configuration and test point used. Public development targets can explain industry direction, but they do not certify an HELE unit or replace a project-specific test record.
Compare degradation with the intended duty
A short acceptance run can establish initial performance at agreed conditions; it cannot demonstrate an entire service life. Durability claims need an operating profile, a starting reference, a degradation metric, planned maintenance and an end-of-life definition. A buyer with frequent cycling should ask what evidence is available for that pattern rather than applying a continuous-operation number by default. The project contract should separate a design target, a tested result and a warranty obligation.
5. What must be agreed before FAT and delivery?
Factory acceptance testing (FAT) is most useful when the test procedure is agreed before manufacture. Decide which utilities will be available at the factory, which conditions can be simulated, and what will instead be verified during site acceptance (SAT). A factory pass does not automatically prove performance after connection to the buyer's water, grid, cooling and downstream hydrogen system.
| Acceptance item | Agree before order release |
|---|---|
| Functional and safety checks | Interlocks, alarms, emergency shutdown, leak/pressure checks, off-spec routing and witness points. |
| Performance demonstration | Flow, energy, gas quality, pressure, stabilization time, instruments and data reporting. |
| Documentation | Approved drawings, equipment list, I/O or cause-and-effect schedule, manuals, calibration, test records and deviations. |
| Site handover | Installation, commissioning, training, spares, warranty limits and who closes outstanding items. |
Write the acceptance procedure before the equipment is built
A useful FAT plan names each test, its preconditions, instruments, duration, acceptance limit, data record and witness point. If a guaranteed flow or purity cannot be demonstrated with the factory utilities, document that limitation early and assign the remaining verification to SAT. Otherwise a buyer can discover at the witness test that the contract promised a number the available setup cannot measure.
The test record should identify the actual equipment configuration and software revision, not just a product-family name. Deviations need an owner and closure method. A passed functional check, a calibrated performance run and a completed documentation package are separate deliverables; buyers should not allow one certificate to stand in for all three.
Safety is a configuration and site question
ISO 22734-1:2025 sets safety requirements for hydrogen generators using water electrolysis. Whether a particular clause, national adoption or certification route applies depends on the supplied system and installation jurisdiction. A reference to the standard is not evidence that a specific HELE package has been certified. Ask for the applicable standard list, the legal entity and model covered by each claimed certificate, and any site-specific requirements the EPC must close.
Hydrogen and oxygen piping, ventilation, gas detection, pressure protection, safe vent locations and emergency-stop interfaces cross the package boundary. The equipment supplier and site designer should agree who supplies, installs, tests and approves each interface. A container does not remove the need for that site review.
Plan the handover after FAT
Shipping, preservation, installation checks, first energization, SAT, operator training and service response are part of the delivery path. The contract should specify whether HELE provides supervision, commissioning, remote support or only documents and equipment. It should also say which spare parts are delivered initially and what data the owner should record during the warranty period. These items shape schedule and operating risk even when they are not part of the factory equipment price.
6. How should buyers compare total project cost?
Put one line in the comparison sheet for every equipment and responsibility boundary. Then add the price of excluded rectifiers, water treatment, chillers, dryers, analyzers, compression, installation, commissioning and spares where the project actually needs them. Compare schedule on the same basis: design approval, manufacturing, witnessed tests, shipping and site readiness can each become the critical path.
Look beyond the purchase order
The buyer's economic question is the cost of reliable hydrogen at the required delivery point, not simply the price of the electrolyzer cabinet. Electricity, water treatment, cooling, planned stack replacement, consumables, maintenance labor, spare inventory and downtime all affect that cost. Their relative importance changes with annual operating hours and the load profile. A low-utilization demonstration system may justify a different purchase choice from an industrial supply system that runs continuously.
Ask bidders to state the basis for maintenance intervals and replaceable items. If a major service item is excluded, the buyer needs its expected replacement scope and price basis to compare lifetime cost. Where that information is not yet available, show it as an open commercial assumption, not as a zero-cost line.
Normalize the schedule as well as the price
One supplier may quote delivery after design approval; another may quote from purchase-order receipt. FAT witness scheduling, export documents, site utility readiness and commissioning can each control the first-hydrogen date. Put those milestones on a common timeline and identify prerequisites owned by the buyer or EPC. A shorter factory lead time does not ensure an earlier operating date if the site interfaces remain undefined.
A low equipment price can still be the right offer—but only after the buyer can see what the EPC or end user must supply. The technical offer should list its assumptions and exceptions so they are resolved before FAT, not discovered during it.
7. What should go into a useful RFQ?
A first inquiry does not need a completed engineering package. It does need enough information to distinguish a stack inquiry from a system project and to reveal the conditions that could change the concept or price.
First-pass information
- Hydrogen end use and delivery point; normal, minimum and peak flow; annual hours and timing of demand.
- Pressure, purity, dew point and impurity requirements at the agreed point.
- Power profile, electrical supply, source-water analysis and available cooling utility.
- Indoor or outdoor site, country, footprint, access, hazardous-area or local code requirements.
- Stack-only, skid, container or wider package expectation; EPC interfaces and desired service support.
- Project stage, desired first-hydrogen date and whether the inquiry seeks budget pricing or a firm technical offer.
For a firm technical comparison
Attach a process or battery-limit sketch, utility data, a one-page load profile and the acceptance requirements. Ask each supplier to return a marked-up equipment list, assumptions and exceptions, guaranteed values with test points, FAT/SAT plan, document list, lead-time milestones and service scope. A bid can then be compared line by line. If the project has not fixed a utility or gas specification, request priced alternatives instead of allowing each supplier to make a different silent assumption.
Questions buyers often ask
Is the stack datasheet enough to compare complete systems?
No. It does not establish the complete-system AC energy boundary, water treatment, gas conditioning, controls or site scope. Use it for stack-level review, then request a separate system guarantee and battery-limit drawing.
Does a nominal hydrogen-flow rating establish gas purity?
No. Purity must be tied to a sampling point, operating condition, analytical method and included conditioning equipment. A figure at a separator outlet may not describe the gas after a dryer or at the user's inlet.
Can a factory test replace site commissioning?
No. SAT still has to account for the actual utility quality, installation, safety interfaces and downstream equipment. FAT and SAT should have distinct test lists and acceptance responsibilities.
Should I size the electrolyzer to peak hydrogen demand?
Not automatically. The answer depends on peak duration, storage, allowed turndown, power availability and whether interruption is acceptable. Show the time-based demand profile so the supplier can compare credible configurations.
Does a containerized system include all site work?
Not by its name. The offer must identify feedwater preparation, grid connection, foundations, ventilation, gas handling, permits, installation and commissioning as included, excluded or supplied by others.