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Home / Hydrogen Generator Sizing Calculator
Sizing tool

Hydrogen Generator Sizing Calculator

Enter the flow you need and how often you need it. The calculator returns the system power, annual electricity consumption and the number of gas cylinders the demand is equivalent to — and every formula it uses is written out below, so you can check the arithmetic yourself.
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See the Formulas
PEM electrolyzer test platform used to measure hydrogen output and energy consumption
Sizing starts with demand and duty cycle. Measured performance data for the specific configuration is confirmed during factory acceptance testing.
Purpose & value

What this calculator does — and what it deliberately does not

It converts a gas requirement into the three numbers that drive equipment selection and operating cost: required output, system power and annual energy. It does not select a product, and its output is not a performance guarantee.

It estimates, transparently

Every formula, constant and assumption is printed on this page. You can reproduce the result with a spreadsheet and check it against your own figures.

It sizes on peak, not average

Peak simultaneous demand sets capacity; average operating demand sets estimated annual gas use. Keep these values separate.

It is not a quotation

Configurations, gas treatment scope, site conditions and measured performance are confirmed in the technical specification and approved quotation.
Calculator

Sizing estimate

Enter peak demand for sizing and average demand for annual consumption. All gas volumes use dry normal conditions: 0°C and 1.01325 bar absolute. NL/min and NmL/min share this reference; do not enter uncorrected actual-volume readings.

Enter the highest simultaneous demand without adding a design margin here.

Use the same unit as peak demand. It must not exceed the peak; annual use is based on this value.

Applied once to peak demand, for equipment capacity only; it does not increase actual annual gas consumption.

Illustrative default. Enter a model-specific AC package value including auxiliaries; external compression, storage and site utilities are excluded unless included in your input.

Illustrative default, not a guaranteed 50 L / 200 bar cylinder yield. Use supplier usable gas after residual pressure, temperature and compressibility corrections.

Optional separate calculation; this does not set peak or average demand above.

Illustrative scenario only. Replace with the fuel cell datasheet consumption at the operating point. This is not an electrolyzer performance figure.

Required output with margin
—
Power at selected design capacity
—
Annual gas demand at average flow
—
Estimated operating electricity per year
—
Cylinder equivalent per year
—
Fuel cell hydrogen demand
—

Use This Estimate in My Enquiry
Estimate only. Values are planning figures based on the reference constants published on this page. Actual performance depends on the configuration offered, measured data, site conditions, water quality and part-load operation, and is defined by the approved technical specification and quotation.
Method

The formulas and constants used

Unit basis
1 Nm³/h = 16.6667 NL/min = 16,666.7 NmL/min
Dry gas at 0°C, 1.01325 bar absolute

Design capacity
Q_design = Q_peak × (1 + margin / 100)
P_design (kW) = Q_design × e_system (kWh/Nm³)

Annual operating demand
V_year = Q_average × operating_hours_per_day × days_per_year
E_year = V_year × e_system
Design margin is not added to average consumption.

Cylinder equivalents
N = V_year / usable_normal_gas_per_cylinder
Use supplier data accounting for residual pressure, temperature and real-gas behaviour.

Optional fuel cell estimate
Q_fuel_cell (NL/min) = electrical_kW × consumption_rate (NL/min/kW)
This separate result does not automatically size the electrolyzer.
Editable planning assumptions. These are not measured guarantees for a product.
Input Default / basis How to use it
System electricity
5 kWh/Nm³, editable
Illustrative AC package assumption; use the selected model and operating profile. External compression and storage are excluded unless your input includes them.
Cylinder usable gas
10 Nm³, editable
Illustrative value; replace with supplier usable volume, not nominal vessel volume × gauge pressure.
Fuel cell consumption
13.5 NL/min/kW, editable
Illustrative scenario only; use the actual fuel cell datasheet.
Normal gas basis
0°C, 1.01325 bar absolute, dry
All flow and volume inputs use this same reference.
Reference

What demand data to obtain before sizing

Application demand must come from the process. Avoid treating a generic example as a guaranteed product selection.
Application Use this input Confirm with
Analytical instruments
Peak and normal flow per instrument at stated reference conditions
Instrument manufacturer
CVD / production lines
Peak simultaneous demand and average operating flow
Process owner / reactor supplier
Renewable integration
Time-series generation and hydrogen demand
Energy and process design teams
PEM system selection
Published system portfolio: 0.5–200 Nm³/h
Model datasheet and approved quotation
Buyer questions

Questions before specification

How is hydrogen generator capacity calculated?

Capacity is set by the highest simultaneous demand, not the daily average: total the flow of every consumer that may run at the same time, then add a design margin. Convert laboratory units first — 1 Nm³/h equals about 16.67 NL/min at the same normal reference conditions.
The editable default is 5 kWh per Nm³ for the AC package. It is a planning assumption, not a product guarantee. Annual energy uses average demand, operating hours and this input; design margin affects capacity only. Use a model-specific load curve for a detailed study.
Enter the supplier-stated usable normal gas per cylinder. The default 10 Nm³ is illustrative; actual usable gas depends on pressure, residual gas, temperature and compressibility. Cylinder equivalents use annual gas demand, not capacity alone.
This calculator is a planning estimate. A quotation reflects the specific configuration, measured performance data, site conditions, gas treatment scope and the energy boundary defined in the technical specification. Treat the estimate as a starting point for the requirement, not as a performance guarantee.
The optional field calculates fuel cell demand using an editable consumption rate. The default 13.5 NL/min per kW is an illustrative scenario, not a universal value. This is a separate result; enter the required peak and average flows explicitly to size the hydrogen supply.
Next step / configuration review

Send us the result and we will check the sizing

Valid calculator inputs and results are included below automatically. Review them before submitting your inquiry. Include the destination country and any procurement specification so the proposed scope can be reviewed against your project.

Project scope

Reference and limits

DOE: PEM stack and system technical targets separates stack and system boundaries. The editable values in this tool are illustrative assumptions, not DOE targets or guarantees for Hele equipment. Standby energy, storage, compression and seasonal load effects need a project-specific review.

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