It is quarter past seven on a wet Tuesday morning at Alsterdorf depot, and the number 109 is being fuelled. There is no diesel smell, no rumbling idle. A technician in Hochbahn overalls connects a thick grey hose, and within eight minutes the bus has enough hydrogen to cover roughly 350 kilometres. By the time it pulls out onto Alsterdorfer Strasse, most passengers boarding at the first stop will not notice anything unusual at all—and that, according to the engineers running Hamburg's hydrogen bus pilot, is precisely the point.
One year ago this month, Hamburger Hochbahn AG put its first series-production hydrogen fuel-cell buses into regular passenger service. The fleet now stands at fifteen vehicles, operating primarily on routes 109 and 114 in the city's north. The pilot is part of a broader commitment by Hamburg's transport authority to phase out diesel buses entirely by 2030, replacing them with a mix of battery-electric and hydrogen-electric vehicles.
The numbers so far
Hochbahn reports that the fifteen buses have collectively covered just over 820,000 kilometres in their first twelve months. Average availability—the share of days a bus is fit for service—stands at 86 percent, which is below the 92 percent average for the existing diesel fleet but above the threshold Hochbahn had privately set as a success benchmark for year one.
Fuel consumption has been higher than the manufacturer's specification. Under real Hamburg conditions—frequent stops, winter heating loads, hilly terrain around Ohlsdorf—the buses consume roughly 9.2 kilograms of hydrogen per 100 kilometres, compared with the rated 8.0. That gap matters because hydrogen remains expensive: the green hydrogen Hochbahn procures through its consortium agreement currently costs around 9.50 euros per kilogram, making fuel costs per kilometre roughly three times higher than diesel.
"Nobody expected cost parity in year one. What we expected was operational learning, and on that front we're ahead of schedule. The drivetrain reliability has been better than any of us predicted." — Thomas Kirschstein, Head of Alternative Drivetrains, Hamburger Hochbahn AG
What passengers notice
Riders we spoke to at Kellinghusenstrasse and Sengelmannstrasse had, for the most part, only vague awareness that their bus was hydrogen-powered. Several mentioned that it was quieter than usual. One regular commuter, a university lecturer who takes the 109 daily, said she had noticed the absence of vibration at stops. "It feels like an electric bus," she said, "which I suppose it technically is."
She is right. A hydrogen fuel-cell bus is an electric bus. The fuel cell converts hydrogen and oxygen into electricity, which drives the motor. The only tailpipe emission is water vapour. The distinction from a battery-electric bus is in how the electricity is generated and stored—and, crucially, in refuelling time. Where a battery bus might need four to six hours on a charger, a hydrogen bus refuels in under ten minutes.
The infrastructure question
Hamburg currently has one dedicated hydrogen refuelling point for buses, located at the Alsterdorf depot. A second is under construction at Hummelsbüttel, expected to open in early 2026. Hochbahn acknowledges that scaling the fleet beyond 40 to 50 vehicles will require a third site, likely in the Harburg area, to cover southern routes without dead-heading buses north for refuelling.
Building hydrogen infrastructure is neither quick nor cheap. Each depot-scale refuelling station costs between four and six million euros, depending on storage capacity and compression technology. And the hydrogen itself must come from somewhere. Hochbahn's current supply is certified green—produced via electrolysis powered by wind energy from Schleswig-Holstein—but the volume is modest. A fleet of 200 buses would require roughly 1,800 tonnes of green hydrogen per year, a quantity that would demand dedicated electrolyser capacity far beyond what the region currently has in place.
Battery or hydrogen—or both?
The debate within Germany's transit sector has sharpened over the past two years. Several cities, notably Munich and Wiesbaden, have committed entirely to battery-electric fleets. Others, including Hamburg, Wuppertal and Cologne, are pursuing a dual-track strategy, using battery buses on shorter, flatter routes and reserving hydrogen for lines with longer ranges, hillier profiles or operational patterns that leave little time for charging.
Hamburg's bet is that its network is too varied for a single technology. The 109, with its 22-kilometre route through residential neighbourhoods, is well suited to hydrogen. The shorter, high-frequency Metrobus lines in the inner city may ultimately be served more efficiently by battery buses charged at terminal stops.
What comes next
Hochbahn plans to order an additional 30 hydrogen buses by the end of 2025, with deliveries expected through 2026. If the second refuelling station opens on schedule, the fleet should reach roughly 50 vehicles by mid-2027. Meanwhile, the engineers at Alsterdorf are compiling a detailed maintenance dataset that they hope will reduce downtime and push availability above 90 percent in year two.
For now, the 109 rolls on. It is quiet, it is punctual, and the only thing coming out of the exhaust is water. Whether that is enough to justify the cost premium over the next decade is a question Hamburg's transport planners are still working to answer. But one year in, the experiment is running—and it is running on schedule.