A company says it’s overcome a major hurdle in the adoption of commercial fuel cell EVs. Loop Energy’s latest can get better fuel economy than a diesel engine, according to . Loop’s new efficiency could finally make fuel cells a viable alternative to diesel in commercial trucks.

The catch, however, is that Loop Energy’s hydrogen fuel cells can outdo diesel engines only at of their respective fuels. Based on the latest prices of diesel in Europe, at about $7.23 per gallon, a truck could travel just over 109 miles on $100 worth of fuel; a comparable truck powered by Loop Energy’s S1200 fuel cell system could travel over 111 miles on $100 worth of fuel.

It’s a small difference of two miles, but it’s nonetheless a step forward, which Loop Energy will speed up adoption of hydrogen-powered EVs in the commercial sector by a few years. Loop’s CEO Ben Nyland went on, saying:

The S1200 brings world-leading fuel efficiency levels for medium to heavy-duty vehicles, crucially making the total cost of ownership lower and bringing fuel cost parity forward by four-to-eight years.

The S1200 fuel cell system has a peak output of 161 horsepower, which isn’t much compared to the average diesel-powered semi, but the proprietary design of Loop Energy’s shows promise. The U.S. company famously known for its diesel engines, , holds more than a 20 percent stake in Loop Energy, making it Loop’s biggest shareholder.

Weaning big trucks — and the freight industry — off diesel has been even harder than getting commuters to switch to EVs. And that’s to say nothing of the little success companies like and have had with FCEVs. Major truck makers like and are are already producing fully-electric models, but would need big batteries that are too heavy to be viable.

Hydrogen fuel cell systems are arguably better for long-haul trucks since they eliminate the need for heavy batteries, and can be refueled (not recharged) about as easily as diesel trucks. But up until now, fuel cell systems had been less efficient than diesel engines. That’s slowly changing thanks to advancements like those from Loop Energy. Now, the only problem FCEVs have to overcome is a major lack of . And that might be a while.