How to Size an AEM Electrolyzer: A Modular Approach from 0.5 to 200 Nm³/h

When selecting an AEM electrolyzer, customers often begin with a power rating: “How many kilowatts do we need?”

A better starting point is hydrogen demand: how much hydrogen is required, when it is needed, how many hours electricity is available, and how the equipment will be maintained.

AEMHY’s approach is to determine total production capacity from hydrogen demand and the power profile, then select an appropriate stack size and combine standardized modules to reach the required scale.

For distributed applications, small industrial users and large renewable hydrogen projects, we recommend evaluating individual stack capacities of 0.5–2, 10–20 and 100–200 Nm³/h, respectively.

Here, a module means a production unit built around an electrolyzer stack. It does not necessarily include a separate water treatment, purification and compression package for every stack.

1. Distinguish hydrogen output from stack and system power

Hydrogen output is commonly expressed in Nm³/h. Electrical input is expressed in kW or MW.

The relationship is:

Stack DC power (kW) = hydrogen output (Nm³/h) × specific DC energy consumption (kWh/Nm³).

Using 4.3 kWh/Nm³ solely as an illustrative conversion basis:

These figures explain the calculation; they are not model-specific energy consumption guarantees.

Total AC system input must also account for rectification losses and auxiliary equipment within the specified boundary. Depending on the scope, this may include circulation, cooling, water treatment, drying, purification and compression.

A 200 Nm³/h stack can therefore be discussed as a building block for a system approaching the megawatt scale, but it should not automatically be labelled a fixed 1 MW unit.

Project specifications must also define the temperature, pressure and moisture basis associated with Nm³/h.

2. Distributed applications: evaluate 0.5–2 Nm³/h modules

Small modules can suit farms, off-grid projects and residential energy installations with a defined need for hydrogen storage, backup power or useful heat.

AEMHY’s QZC0.5 and QZC2 use a single-cell active area of 100 cm². Their respective 10-cell and 40-cell configurations correspond to hydrogen outputs of 0.5 and 2 Nm³/h under specified operating conditions.

Cell count alone does not establish output: current density, Faradaic efficiency and operating conditions also matter.

Potential pathways include storing hydrogen for later fuel cell generation, recovering useful heat where demand exists, or supplying a suitably designed hydrogen or hydrogen-blend combustion application.

Hydrogen blending is not a direct connection to any existing burner. Equipment compatibility, permitted blend composition, piping and applicable local requirements must be evaluated.Hydrogen blending considerations from Southwest Research Institute

For daily electricity balancing, compare the complete hydrogen pathway with battery storage. Longer storage periods, backup requirements and useful heat demand may provide reasons to assess hydrogen, but the electrolyzer price alone cannot determine project economics.PNNL overview of hydrogen energy storage

3. Industrial on-site hydrogen: start with 10–20 Nm³/h

For small factories, AEMHY recommends evaluating QZC10 and QZC20: 10 and 20 Nm³/h stacks with 50-cell and 100-cell configurations, respectively.

First establish daily consumption, peak flow, acceptable supply interruptions, delivery pressure and gas quality.

For example, a factory requiring 160 Nm³ per day would need an average production rate of:

• 10 Nm³/h if hydrogen is produced for 16 hours;

• 20 Nm³/h if production is limited to eight hours.

These are baseline calculations before allowing for maintenance, varying loads and storage arrangements.

Continuous production users should also compare a single larger module with multiple smaller modules. Modular layouts can support staged investment and maintenance planning, but continued supply during servicing requires suitable isolation, power distribution, controls and auxiliary equipment.

4. Renewable hydrogen: consider 100–200 Nm³/h building blocks

A large wind or solar hydrogen project does not require an indefinitely larger individual stack.

For AEMHY’s current AEM product platform, we favour QZC100 and QZC200 as standardized building blocks for larger installations, expanding total capacity by combining modules.

The engineering priorities are:

Manufacturing consistency. Increasing stack size places greater demands on component uniformity, sealing, assembly and flow distribution. Standard modules can support repeatable production and acceptance processes; actual manufacturing yield must still be demonstrated with production data.

Serviceability. Module size affects handling, replacement, refurbishment and spare-part planning.

Power matching. Where operating conditions permit, fewer modules can run when renewable electricity availability falls.

Phased expansion. Additional modules can be installed as electricity supply and hydrogen demand grow.

For example, ten 200 Nm³/h stacks provide a nominal combined output of 2,000 Nm³/h. When available power supports approximately 200 Nm³/h, the operator can compare running fewer modules at higher load with operating all modules at low load.

The preferred dispatch strategy depends on efficiency, start-up losses, temperature management, cycling, gas quality and auxiliary equipment. More modules do not automatically guarantee better performance.

IRENA notes that renewable power response can also be constrained by equipment such as gas processing and compression.IRENA discussion of electrolyzer system design

5. Why does AEMHY prioritize stacks up to 200 Nm³/h?

Our position is not that stacks above 200 Nm³/h have no value.

It is that, for the applications and product platform AEMHY currently addresses, standardizing 100–200 Nm³/h stacks and combining them offers an attractive engineering route to larger systems.

Larger stacks may reduce some unit costs while creating additional manufacturing and maintenance demands. Too many small modules can increase the cost of valves, electrical connections, power supplies and controls.

A practical design can combine standardized stacks with appropriately shared water treatment, cooling and gas processing infrastructure. Shared equipment must still meet the required reliability and operating range.

IRENA distinguishes stack scaling from balance-of-plant economies and emphasizes the influence of design and application. Our preferred module size is therefore an AEMHY engineering choice, not a universal industry optimum.IRENA, Green Hydrogen Cost Reduction

6. What information is needed for sizing?

Before requesting a quotation, prepare:

1. Daily hydrogen demand and peak flow;

2. Available production hours;

3. Grid, solar, wind or hybrid power arrangements;

4. Delivery pressure, purity and dew point requirements;

5. Storage capacity and acceptable supply interruptions;

6. Expansion plans and maintenance constraints.

The objective is to match demand, power availability, module size and service strategy.

AEMHY supports selection discussions for QZC0.5, QZC2, QZC10, QZC20, QZC100 and QZC200. Contact our team to assess individual stack capacity and the appropriate modular configuration.

Product groupings reflect AEMHY’s selection approach. Available configurations, performance, operating limits and scope of supply are governed by model-specific documentation and project agreements.