Could Hydrogen Engines Be an Alternative to Fuel Cells?

Future Technologies
Author: Lütfi Mete Odabaşı
Creation: 19 October 2026

Burning hydrogen takes over existing engine know-how and the supply chain, but leaves a path split in two with the fuel cell on efficiency.

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Hydrogen engines are internal combustion engines that burn the fuel directly instead of using it to generate electricity in a fuel cell; because they can leverage existing engine manufacturing knowledge and supply chains, they are seen as a serious alternative for heavy commercial vehicles. But their efficiency is markedly lower than fuel cells, NOx emissions must be brought under control, and refueling stations are still scarce. So the answer is clear: reasonable in some scenarios, still a promise in others.

Highlights

A fuel cell vehicle can operate nearly twice as efficiently as an engine that burns hydrogen
Hydrogen's flammability limits are 4-75% by volume; gasoline's is only 1.2-7.6%
Volvo has begun road testing hydrogen-powered heavy trucks and before 2030 plans a launch
Cummins announced it can reduce NOx levels to as low as 0.008 g/hp-hr announced that it can reduce them to levels as low as
Toyota is developing these engines primarily through racing, not for road use

What's the Difference Between Burning Hydrogen and Passing It Through a Fuel Cell?

Think of the gasoline engine we know: instead of gasoline, it injects hydrogen, a spark ignites it, and the hydrogen burns. That's it. A fuel cell is an entirely different thing: it converts chemical energy into electrical energy directly, without combustion, and delivers that electricity to an electric motor. A daily analogy: one person burns wood in a stove to keep warm, while the other gets the same energy from an efficient heat pump. Both get the job done, but the way they use energy is very different.

The most tangible consequence of this difference is efficiency. Peer-reviewed comparisons show that a fuel cell vehicle is nearly twice as efficient as an internal combustion engine vehicle that burns hydrogen directly. When hydrogen is an expensive and scarce fuel, this difference isn't small, it's massive. Think in kilograms: from the same tank, one gets you an extra hundred kilometers, the other doesn't. For anyone on a tight budget and range, that's a serious argument.

On the other hand, the fuel cell has its price: expensive materials like platinum, a complex system, and high cost. The hydrogen engine, meanwhile, is a familiar face. So the comparison is between "efficient but expensive" and "less efficient but familiar and cheap."

The Biggest Trump Card of Hydrogen Engines: Existing Production Infrastructure

Put yourself in an engine manufacturer's shoes. You have two options: build fuel cell technology from scratch, or produce a hydrogen version while preserving your existing engine knowledge, foundries, supply chain, and assembly lines. The latter lowers R&D costs and speeds up time to market. Cummins emphasizes that this approach could achieve greenhouse gas reductions similar to fuel cells at a lower upfront cost.

The second advantage is hidden in the heavy vehicle. Internal combustion engines operate most efficiently under high load; trucks spend almost their entire lives under high load. So the efficiency deficit of H2-ICE stings less in trucks than in urban passenger vehicle use. Also, there is no difference for the truck driver: the tank empties, you refuel in a few minutes, and you're on your way. Hydrogen's fast refueling time genuinely pays off here.

Hydrogen also has a technical character: its ignition limits are incredibly wide. It can ignite in any mixture between 4% and 75% by volume, whereas gasoline only burns in the 1.2-7.6% band. A wide ignition range means flexible combustion strategies that adapt to varying loads. For engine engineers, this is something like a gift package.

Weak Point 1: Efficiency Loss and Where the Energy Goes

In a fuel cell, most of hydrogen's energy is converted directly into electricity. In a combustion engine, however, a significant portion of the same energy is lost as heat; you pay the price of thermal losses, friction, and the exhaust. The fact that a fuel cell vehicle is twice as efficient means you get half the range with the same amount of hydrogen. Since tank volume is already a problem with hydrogen (gas takes up space even when compressed), the range math tips in favor of the fuel cell.

That's why the "but engines are cheaper" argument needs to be calculated over the fuel's lifetime to see if it has any real substance. Cheap engine + expensive fuel consumption, or expensive system + low fuel consumption? This question turns daily in trucking companies' ledgers, and the answer hasn't fully settled yet.

Weak Point 2: A "Clean" Engine But It Produces NOx

When hydrogen burns, no carbon dioxide is released; this is H2-ICE's biggest environmental argument. But the nitrogen in the air falls in love with oxygen at high temperatures, and nitrogen oxides (NOx) form. Especially when a stoichiometric mixture, i.e. one perfectly balanced with air, is burned, the combustion temperature soars and NOx production becomes serious. At low lambda values too, the engine can emit high NOx; that's why accurate prediction and control of emissions is critical.

The good news: the problem is manageable. Cummins announced that it has reduced NOx to the level of 0.008 g/hp-hour, which remains four times below the EPA's 2027 requirements, and that CO2 dropped by 99.7%. Cooled exhaust gas recirculation and advanced aftertreatment systems make these figures possible. The bad news is the existence of criticism: on technology forums, objections are raised that these engines may not be able to deliver diesel-equivalent torque or comply with tightening NOx limits; suppliers were even among those openly voicing this cautious view.

Weak Point 3: Fuel Stations Are Still Few

The most beautiful engine in the world turns into a coffin if you don't have the fuel. Volvo Group itself says that hydrogen mobility will only become commercially viable when vehicles, fuel supply, and refueling infrastructure scale up together. In other words, even some of the companies that produce the engines admit that the infrastructure problem has not been solved.

The hopeful side is cost: the cost of producing hydrogen from renewable electricity is estimated to fall by up to 30% by 2030. Players such as Volvo, Daimler Truck, Toyota, Bosch and Air Liquide have announced coordinated plans covering the entire hydrogen value chain and are asking the EU for financing synchronized with the grids. So the industry has a plan for the problem; but a plan and a fueled-up hydrogen station are not the same thing.

What Are Manufacturers Doing? Where Toyota, BMW, Volvo and Cummins Stand

Toyota yarış pistinde, BMW fabrika sahasında, Volvo 2030 hedefinde: büyük üreticiler hidrojen motoru ile yakıt hücresini aynı anda pusuda tutuyor.

There is real movement in the field - you don't need to be an optimist to say so:

Toyota is advancing two hydrogen engine technologies in parallel in the Super Taikyu racing series and has announced its goal of commercializing hydrogen combustion engines in 2026 and increasing range by 20%. In September 2026, a hydrogen combustion hybrid (EREV) patent also surfaced; according to secondary sources, production could begin in 2027 with a few hundred vehicles per month and scale to 400,000 units annually by 2028. But note: Toyota is developing these engines primarily through racing, not for road use. And when it comes to the real road-going hydrogen vehicle, the fuel-cell Mirai still seems to be the answer.
BMW has added two 40-ton and one 18-ton hydrogen-powered trucks to its logistics fleet; its Regensburg plant will use hydrogen tractor-trailers and forklifts from 2026 onward. BMW has also ordered two fuel-cell trucks for the same route; they will operate on the Leipzig–Landsberg–Nuremberg corridor. So BMW, too, is walking both paths.
Volvo has begun road testing heavy trucks with hydrogen combustion engines and plans a launch before 2030. At the same time, it is also developing fuel-cell trucks through the cellcentric joint venture. It isn't putting all its eggs in one basket.
Cummins 15L introduced its hydrogen engine in 2022; X15N the X15H is expected for 2027. The 6.7L hydrogen engine is based on a proven spark-ignition platform and promises ultra-low NOx.

The common pattern is clear: the big players are funding both hydrogen paths. No one is sacrificing one for the other, because no one knows which one will win.

Where Does It Make Sense: Passenger Cars or Trucks?

Let me put everything I've described so far into a table; seeing the two powertrains side by side against the same criteria makes everything clear:

Criterion	Hydrogen Combustion Engine	Fuel Cell (FCEV)
Efficiency	Low; roughly half that of a fuel cell	High; chemical energy is converted directly into electricity
Zero emissions	No; NOx is produced and requires treatment	Yes; only water from the exhaust
Cost and production	Low upfront cost, existing engine infrastructure	Expensive system, precious materials such as platinum
Best-fit scenario	Heavy commercial vehicles operating under high loads	Road use focused on range and efficiency
Refueling	Fast, close to gasoline/diesel habits	Fast; both depend on infrastructure

The general consensus in the industry also aligns with what the picture shows: heavy-duty vehicles are the most sensible scenario; in passenger cars, fuel-cell FCEVs maintain their dominance. Why is the hydrogen engine weak in the urban compact class? Because city driving means low loads and stop-and-go traffic; you never reach the engine's most efficient operating zone. A truck, on the other hand, lives on the highway at a constant high load; that's where the engine is at its best.

Promise or Reality? Here's the Fine Line

The promise side is real: existing engine manufacturing know-how and supply chain, low upfront costs, high load efficiency in heavy-duty vehicles, and fast refueling are tangible advantages. These are not marketing talk, they are factory facts. Cummins, Volvo, and BMW's truck programs show these advantages being tested in the field.

The reality side is also harsh: roughly half the efficiency compared to fuel cells, the NOx problem and mandatory aftertreatment systems, a fuel infrastructure that still hasn't scaled, Toyota's racing-focused development instead of road use, and 2026 commercialization targets for passenger vehicles that have yet to be verified with a concrete product. Market figures are also watery: different reports cite magnitudes that differ severalfold for the same market, because even the way they define the market is different. Rather than wearing the numbers like a necklace, it's healthier to watch actual product launches year by year.

My assessment is this: H2-ICE is on its way to becoming a real player not in passenger cars, but in heavy commercial vehicles. If you manage a truck fleet, it's wise to keep an eye on hydrogen-powered trucks. If you're waiting to buy your next car because it will have a hydrogen engine, there's no point in waiting right now; even Toyota is still putting the fuel-cell Mirai in its showroom. Is the hydrogen engine a "transitional technology" or a permanent alternative? The answer changes depending on which vehicle class you're talking about - and the most honest answer today is yes for truck drivers, not yet for sedan buyers.