35 MPa vs. 70 MPa Hydrogen Fueling Systems

- H35 and H70 refer to nominal vehicle storage pressure classes: 35 MPa is approximately 350 bar or 5,000 psi; 70 MPa is approximately 700 bar or 10,000 psi.
- H35 remains common for buses, forklifts and many commercial fleets, while H70 is established in light-duty passenger vehicles.
- Heavy-duty hydrogen fueling is evolving. Current research and protocol development consider both H35 and H70, so “truck equals H35” is not a universal design rule.
- H70 generally requires higher-pressure station storage, compatible components, more demanding pressure management and, for fast fueling, carefully controlled hydrogen delivery temperature.
- The right system starts with the vehicle OEM requirements and duty cycle—not with a generic pressure preference.

H35 and H70 describe the nominal working pressure of the vehicle’s compressed hydrogen storage system. They do not describe every pressure inside the station. To transfer hydrogen into a vehicle, the station storage and dispensing system must operate above the vehicle pressure under controlled limits defined by the applicable equipment design and fueling protocol.

The U.S. Department of Energy identifies 350 bar as H35 and 700 bar as H70. DOE guidance also notes that onboard storage technology directly affects the design of the delivery infrastructure. In other words, the vehicle and station must be treated as one fueling interface, not as unrelated products. 

H35 is widely associated with buses, material-handling vehicles and commercial fleets. These applications often have more room for onboard storage than passenger cars and operate from fleet depots with predictable schedules.

That does not make every H35 station identical. A forklift station, a city-bus depot and a heavy-truck hub can have very different hydrogen demand, fill mass and peak flow. Compressor capacity, the hydrogen storage cascade system, dispenser configuration and backup strategy must be sized for the actual operating profile.

SAE J2601/2 provides performance requirements for 35 MPa heavy-duty transit-bus and vehicle fueling. It applies to heavy-duty vehicle storage capacities above 10 kg and is separate from the light-duty SAE J2601 protocol. 

H70 is common in passenger fuel cell vehicles because doubling the nominal storage pressure increases the amount of hydrogen that can be carried within a limited vehicle footprint. The trade-off is a more demanding station interface.

For fast H70 fueling, the design must manage pressure rise and hydrogen temperature as the vehicle tank fills. SAE J2601 covers both H35 and H70 light-duty pressure classes and defines process limits affected by ambient temperature, fuel delivery temperature, maximum flow rate, pressure-ramp rate and the vehicle’s initial tank pressure. The standard includes T40, T30 and T20 fuel delivery temperature categories. 

No. That is a useful historical shortcut, but it is no longer a sufficient engineering rule.

DOE and NREL work on medium- and heavy-duty fueling evaluates both H35 and H70. A 2024 NREL presentation lists research metrics ranging from 60 to 300 g/s, vehicle storage above 10 kg and up to 200 kg, and a 100 kg target fill. These are research and protocol-development metrics—not universal commercial station specifications—but they show why vehicle type alone cannot determine the pressure class.

Compression and Storage

The compressor and station storage must support the required dispensing pressure across the hydrogen source’s expected inlet-pressure range. A delivered-gas station supplied by hydrogen tube trailers must also account for declining trailer pressure and usable—not merely nominal—hydrogen inventory.

Higher target pressure usually increases the demands placed on compressors, storage vessels, valves, piping and seals. A staged cascade can preserve the highest-pressure hydrogen for the end of the fill while lower-pressure banks serve the earlier stages.

Cooling and Fueling Control

Rapid compression of hydrogen into the vehicle raises gas temperature. Cooling duty is therefore connected to fill rate, ambient conditions, vehicle storage and protocol—not simply to the H35 or H70 label.

For light-duty fueling under SAE J2601, fuel delivery temperature and pressure-ramp controls are integral to the protocol. Heavy-duty high-flow systems require a separately validated strategy suited to the vehicle and applicable standard.

Cost and Throughput

H70 should not automatically be treated as “better” because it is higher pressure. The business question is whether the vehicle fleet requires it and whether the added compression, storage, cooling and component requirements produce an operational benefit.

Likewise, H35 is not automatically the lower-cost answer. A high-throughput fleet may require substantial compression, storage and redundancy. Project cost should be evaluated against kg/day, peak kg/hour, back-to-back fills, station availability and lifecycle maintenance.

Confirm these six inputs before selecting equipment:

1. Vehicle OEM pressure class and fueling interface;
2. Hydrogen required per vehicle;
3. Vehicles per day and peak vehicles per hour;
4. Target fill time and back-to-back fueling requirement;
5. Hydrogen supply method, purity and inlet-pressure range; and
6. Destination-country codes, site conditions and required project scope.

If a station must serve more than one vehicle class, evaluate separate dispensing paths, storage strategy, control logic and future expansion during the concept stage. A dual-pressure label alone does not confirm that the station can satisfy both duty cycles.

For the complete system process, read how a hydrogen fueling system works.

After selecting the pressure class, calculate the required hydrogen station capacity from vehicle demand, peak fills and equipment recovery.

Rein provides hydrogen refueling station equipment including compressors, high-pressure storage cascades, unloading and filling equipment, sequence control valve groups, dispensers and station controls. Rein also supports system integration and hydrogen engineering services for project-specific station requirements.

The correct configuration depends on more than pressure. Share your vehicle type, daily hydrogen demand, peak fueling schedule, hydrogen source and project country. Rein’s engineering team can use these inputs to discuss an appropriate equipment and integration scope.

Request an H35/H70 Configuration Review

Is 35 MPa the same as 350 bar?

Yes. A nominal pressure of 35 MPa equals 350 bar and is approximately 5,000 psi. It is commonly identified as H35.

Is 70 MPa the same as 700 bar?

Yes. A nominal pressure of 70 MPa equals 700 bar and is approximately 10,000 psi. It is commonly identified as H70.

Can one hydrogen station support both H35 and H70?

It can be engineered to support both pressure classes, but the compressor, storage, dispenser, cooling, controls, vehicle interfaces and peak demand must be evaluated together. Two dispenser labels do not by themselves make a complete dual-pressure design.

Does a 70 MPa station always refuel faster?

No. Fill time depends on vehicle capacity, initial tank conditions, mass-flow limits, delivery temperature, storage pressure, compressor recovery and the fueling protocol. Higher pressure alone does not guarantee a faster fill.