PEM electrolyzer efficiency figures are comparable only when they describe the same energy and hydrogen boundaries. Check whether a value covers the stack, the supplied package or the wider installation. Then align operating conditions and the definition of delivered hydrogen.
This guide provides a comparison method rather than an efficiency ranking of suppliers. Request model-specific data for the system or stack being proposed.
Cover illustration: conceptual scene; configuration varies by project.
1. Define the electrical measurement boundary
Record where electrical input is measured and which loads are included. A stack DC input figure and a package AC input figure cover different equipment. Ask how the rectifier, pumps, cooling, controls and gas treatment are treated, and identify external loads excluded from the reported value.
The U.S. DOE PEM electrolysis target table separates stack and system measures. Its development targets and stated assumptions should not be presented as a manufacturer’s current product guarantee.
2. Complete an efficiency comparison record
| Comparison item | Record for each proposal | Reason to resolve differences |
|---|---|---|
| Energy input | AC or DC meter location and included auxiliaries | Different boundaries include different loads |
| Hydrogen basis | Mass or volume, reference conditions and delivery point | The denominator must use the same basis |
| Gas specification | Delivered pressure, quality and treatment included | Additional processing changes the comparison |
| Operating point | Load, temperatures and other stated test conditions | One operating point does not describe every duty |
| Test period | Steady operation, start-up, standby and measured interval | Short tests and annual duty are different questions |
| Equipment condition | Configuration, conditioning state and relevant age | Evidence should match the proposed product |
| Percentage efficiency | LHV or HHV basis and calculation method | Percentages need a common energy convention |
3. Calculate specific consumption on a consistent basis
For a measured interval, divide the electrical energy within the agreed boundary by the hydrogen delivered within the agreed gas boundary. State the resulting unit, such as kWh per kg of hydrogen. If volume is used, retain the agreed reference temperature, pressure and reporting basis.
For a changing duty, total the energy and hydrogen over the same interval before calculating the ratio. Do not simply average individual percentage values or combine a full-load energy result with a different output assumption.
4. Review the proposed operating profile
Ask for relevant evidence at the loads your process will use, including start-stop and standby treatment where material. Keep the evidence for rated-duty performance separate from assumptions used to estimate annual operating costs.
When comparing a package with an externally cooled or externally compressed arrangement, show the external services separately. An apparently lower package input may simply leave more equipment outside the named boundary.
5. Agree acceptance before relying on the number
Identify the measurement points, methods, calibrated instruments, test duration, operating conditions and acceptance criteria. Record how uncertainty and deviations will be handled. The required verification belongs in the purchase specification and test plan.
Use the quotation-comparison worksheet when energy figures form part of a commercial evaluation. It keeps equipment price, missing scope and operating assumptions visible as separate questions.
Request configuration-specific performance information
Send the proposed output, gas pressure and quality, load profile, package boundary, utilities and any efficiency figures you need to compare. State whether your requirement concerns stack DC, package AC or the whole installation.
Published by Hele Titanium Hydrogen. Updated 17 October 2026. No supplier ranking or product efficiency guarantee is established by this comparison method.
