On Friday, Stadler unveiled a narrow-gauge version of its Flirt H2 hydrogen train at its plant in Erlen, Thurgau. It is the latest step in a project that quietly does something the Power-to-X community has argued for years: it puts renewable hydrogen to work where electrification is hard — and it runs on hydrogen produced locally from sunshine.
How a hydrogen train actually works
The Flirt H2 is an electric multiple unit. Its fuel-cell module sits in the middle car and behaves like an onboard charger: it converts hydrogen into electricity and tops up the batteries that drive the train. That architecture lets the train run efficiently on routes with no overhead line — without a drop of diesel.
Why hydrogen, when trains already run on electricity
Electrified rail is clean rail. But a large share of the world’s track has no catenary. In the United States, only around one percent of the network is electrified, and many operators still run diesel out of necessity. Retrofitting overhead lines and substations is slow and expensive. On long routes that are not electrified — or only partly — a hydrogen drivetrain lets operators retire diesel without rebuilding the infrastructure first. Stadler puts numbers on it: the ten hydrogen trains destined for the Sardinian network are expected to avoid more than 2,100 tonnes of fossil CO₂ every year compared with diesel.
This is, in SPIN’s terms, a clean case of defossilisation. The problem with a diesel train is not that it burns fuel; it is that the carbon in that fuel is fossil. Replace the fossil energy carrier with renewable hydrogen, and the fossil carbon disappears from the route.
The detail that matters most: where the hydrogen comes from
For a Power-to-X audience, the headline is not the train — it is the fuel. In Sardinia, three electrolysers have been built to produce green hydrogen locally, using photovoltaic electricity. The trains therefore run on hydrogen made on the island from local sunlight. According to Stadler, this combination — hydrogen rail fed by dedicated local renewable electrolysis — is unique worldwide; other European hydrogen fleets rely on industrial hydrogen.
That distinction is everything. A hydrogen train only delivers a climate benefit if the hydrogen itself is renewable. Run it on grey, fossil-derived industrial hydrogen and much of the advantage evaporates. The Sardinian model — solar electricity → electrolysis → hydrogen → mobility — is a Power-to-X value chain in miniature, and it buys something diesel never could: energy autonomy. Operators producing their own hydrogen from local renewables are insulated from the geopolitics of fuel supply, from the Strait of Hormuz to volatile diesel markets.
What is new on this train
The engineering novelty is the bespoke, lightweight running gear designed for Italy’s narrow-gauge lines, which permit only low axle loads. Otherwise the working principle is the same as the first Flirt H2, delivered to California in 2019. One quirk reveals how tightly the technology is packed: the corridor through the middle car is so narrow that only one person can pass at a time, because it houses the hydrogen tanks and the fuel cells. On the standard-gauge model, that corridor is wider.
Range, and a couple of world records
On a single fill, Stadler’s hydrogen trains can cover 600 to 1,000 kilometres a day; with fresh batteries, even more. On the test track in Pueblo, in the United States, the first Flirt H2 ran roughly 2,800 kilometres nonstop on one tank of hydrogen — a world record, and the second for the Flirt family: in December 2021 a battery-electric Flirt set the record for the longest journey by a regional train in pure battery mode.
Is hydrogen safe on a train?
Hydrogen is a volatile gas and, mixed with oxygen, can form an explosive oxyhydrogen mixture. The safety principle is straightforward: never let escaping hydrogen accumulate. On the Flirt H2, any hydrogen that escapes is vented upward into the open air. Stadler reports no such incidents with its hydrogen trains to date.
The order, and how the trains reach Italy
The Italian contract covers 21 hydrogen trains and eight battery trains, worth around €350 million, ordered by Trasporti Regionali della Sardegna, Sicily’s Ferrovia Circumetnea and Calabria’s Ferrovie della Calabria. Because the narrow-gauge trains cannot run on the Swiss standard-gauge network, they leave Thurgau on flatbed wagons or by truck, before being ferried across to Sardinia and Sicily.
Why SPIN is watching
A hydrogen train is not the only way to defossilise rail, and where catenary makes sense it usually wins. But the Sardinian project is a useful proof point for the wider Power-to-X case: renewable electricity, turned into hydrogen close to where it is used, can defossilise transport that would otherwise stay on fossil fuel for decades. The train is the visible part. The electrolyser is the point.
Power-to-X Congress Switzerland 2026
Reality Check with Net Zero — 22 September 2026, 10:00–18:00, Kursaal Bern.
The Power-to-X Congress Switzerland 2026 is co-organised by energie-cluster.ch and the Swiss Power-to-X Collaborative Innovation Network (SPIN), with Réseau H2 Suisse Romande as partner. Join the conversation on where Power-to-X really stands on the road to net zero.