What you need to know:
- Truck makers are being pulled in too many directions as they juggle multiple low-emission technologies, creating what NACFE's Mike Roeth calls a “messy middle” for the industry.
- NACFE's 2025 Run on Less showed that all four powertrains—battery-electric, natural gas, diesel, and hydrogen fuel cell—can perform well, but none offers a universal solution due to ongoing challenges with infrastructure and cost.
- Initial results revealed strong but varied performance across technologies: electric trucks excelled in efficiency, natural gas trucks matched diesel capability at high weights, modern diesel trucks achieved high fuel economy with renewable fuels, and hydrogen trucks performed well in urban routes but are constrained by limited hydrogen infrastructure.
- The industry's decarbonization path will be complex and multi-fueled, with no single winner emerging soon—meaning fleets will continue relying on a mix of diesel, natural gas, renewable diesel, and potentially hybrid options as the transition continues.
As truck manufacturers race to slash greenhouse gas emissions with new powertrain technologies, some industry experts warn that the push to go green could be pulling them in too many directions at once.
That's the concern of Mike Roeth, executive director of the North American Council for Freight Efficiency (NACFE), who says OEMs may be spreading themselves too thin as they juggle multiple low-emission technologies.
"I'm worried that truck OEMs are spreading themselves across too many technologies, which could reduce their scale," Roeth told Clean Trucking. "Natural gas is established, but some are passing on natural gas engines while others stick with electric or diesel. We're already seeing the first signs that they can't manage it all, possibly due to the 2027 NOx standards. It's shaping up to be a messy future for OEMs."
Inside the "Messy Middle"
That messy future was on full display during NACFE's 2025 Run on Less demonstration, held from September 8 to 26.
This year's edition—appropriately titled The Messy Middle—tracked 13 fleets across North America to measure freight efficiency across a mix of powertrains: battery-electric, hydrogen fuel cell, natural gas, and diesel.
After three weeks on the road, NACFE's interim report found that each technology proved capable under certain conditions, but none yet offers a one-size-fits-all solution. Infrastructure, cost, and vehicle weight remain persistent hurdles.
"These four powertrain solutions represent currently available options for fleets today," Roeth said. "This run was about the long-haul and where we believe is where the messiness comes in. It's not a competition. Everybody wants to do well."
Participating vehicles included a range of alternative-fuel and conventional trucks. The battery-electric group featured the Tesla Semi, the Windrose R700, the Freightliner eCascadia, and the Volvo VNR Electric.
The natural-gas category consisted of three models powered by Cummins' new 15-liter X15N engine: the Kenworth T880, the Kenworth T680, and the Peterbilt 360.
Diesel entries included an International LT sleeper equipped with the upcoming Cummins X15 2027 NOx engine, a Volvo VNL operating on B99 biodiesel, and a Freightliner Cascadia and a second International LT running on standard diesel.
Finally, the hydrogen fuel-cell (FCEV) segment was represented by two examples of the Hyundai XCIENT.
"All of the trucks performed better than we thought in both uptime, performance in range, efficiency, and capability. The flip side to that coin is that we have a lot of these technologies to deal with," Roeth explained. "But we didn't have a hybrid powertrain. It would have been nice to have one for comparison."
[Related: Check out the new ReVolt diesel-electric hybrid Class 8 semi]
Fleets face tough choices
For fleet operators, the growing menu of powertrain options is both a blessing and a burden. The choices now include long-range battery-electric trucks like the Tesla Semi, advanced natural gas engines such as Cummins' X15N, and a growing supply of renewable fuels.
While battery-electric vehicles (BEVs) are improving quickly, they still face steep challenges in infrastructure, cost, and payload impact. In contrast, natural gas trucks are nearly on par with diesel in power and refueling time—and can tap into existing fueling infrastructure while offering significant emissions reductions, especially when running on renewable natural gas (RNG).
[Related: California's RNG-fueled fleets mark 5 years of carbon-negative transit]
Hydrogen fuel cells, meanwhile, remain a promising but uncertain option. Hyundai's XCIENT FCEV was the only hydrogen semi represented at this year's event, following the bankruptcies of Nikola Motors and Hyzon Motors.
Despite funding setbacks for clean hydrogen projects, the technology continues to attract attention for its range and refueling advantages, despite some overseas safety concerns and operational issues.
Initial findings: Progress, but no clear winner
If there's one takeaway from this year's event, it's that no single powertrain has emerged as the ultimate solution in regards to slashing carbon emissions, fleet affordability, and available infrastructure.
Battery-electric trucks were standout performers for efficiency and uptime.
One truck logged 465 miles on a single charge. Another covered 3,676 miles in 18 days, operating in dual shifts with 52% uptime and just 13% charging time. A third tallied 875 miles in one day using only public chargers.
"Tesla and Windrose knocked it out of the park," said Roeth. "Saia ran two shifts with the Tesla Semi, hitting 460 miles in one day on a single charge at 750 kW. On their Stockton–Bakersfield route, they only need to charge up to 40% for city runs, going from 20% to 80% in just 45 minutes."
Still, charging remains a major roadblock. Building a large-scale depot can take anywhere from nine to 36 months due to utility and construction delays.
Natural gas trucks, powered by the new Cummins X15N, also made an impression. "Fleets wanted to show these engines can do the same work as diesel," Roeth said. "They were hauling doubles and triples legally at over 120,000 pounds gross, and they performed great—even more so when using RNG."
Diesel-powered rigs gave impressive performances as well.
The Frito-Lay Volvo VNL tractor was running on B100 biodiesel, and most of the fuel used in California was renewable diesel. While some industry observers may believe diesel is on its way out, this year's run demonstrated that modern diesel engines—whether powered by traditional diesel, renewable diesel, or biodiesel—are likely to remain an important part of the trucking landscape for years to come.
Renewable diesel and biodiesel both offer environmental perks, but they also have some downsides for long-haul trucking, like lower energy content that cuts into mileage, higher prices, and issues with cold weather and fuel availability. Traditional diesel engines still deliver the power and durability truckers rely on, but they're not without problems either, including their environmental impact and the high maintenance costs that come with today's complex emissions systems.
According to Roeth, diesels combined 22,000 miles in 18 days, averaging 11.6 mpg. To compare, "the national average for diesel is around 7.5 mpg. That's decarbonizing—moving the same freight with less fuel. Less NOx means less pollution."
Hydrogen trucks, meanwhile, demonstrated solid performance in urban settings, though cost and infrastructure remain significant barriers. The two Hyundai XCIENTs—one operating in Dallas, the other in Los Angeles—showed strong uptime and efficiency of 7.5–8 miles per kilogram of hydrogen, comparable to diesel fuel economy.
"They performed well in stop-and-go conditions where diesel usually struggles," Roeth said. "Hydrogen can work but only with the right routes, infrastructure, and access to clean hydrogen. Without that, it's a hard sell."
The bottom line
If the 2025 Run on Less initial results prove anything, it's that trucking's decarbonization journey won't be a straight line. Electric, hydrogen, natural gas, and diesel technologies are all advancing—but each brings its own trade-offs.
Hopefully, the next Run on Less, planned for 2027, will include a diesel-hybrid, as Roeth previously suggested.
"One of my hopes for the run is that the industry notices to keep up efficiency on diesels, natural gas, and bio diesel. We can chew gum and walk at the same time. We're going to focus on what we believe the future is and do it extremely well," concludes Roeth.
For truck makers and fleets alike, the "messy middle" may be the industry's new normal for years to come.
