Why you shouldn't delay your transition to zero-emission fuel cell buses

While diesel-hybrid buses may seem like a lower‑risk interim solution, they lock your agency into continued diesel dependence and harmful emissions; and leave you trailing in the race for zero-emission vehicle (ZEV) funding, regulatory compliance and meeting your sustainability goals. Choosing fuel cell electric buses (FCEB) is the smarter path that fully aligns with long‑term operational, environmental and financial objectives, while maximizing funding opportunities on top of the Low or No Emission Grant Program (Low-No).

FCEBs are the only vehicles that provide a true one‑for‑one replacement of diesel buses, delivering all the benefits of zero‑emission operation – no tailpipe pollutants or greenhouse gases – without impacting service. With refueling times of just 10-15 minutes (as opposed to several hours for battery electric charging) and ranges of 300-450 miles per fill, FCEBs are especially well suited for long, high‑utilization routes.

Despite the current higher cost of vehicles, ongoing investments in fuel cell engines, hydrogen tanks, and electric drivetrains will reduce costs over time. In the meantime, to bridge the gap, FCEBs benefit from significant funding thanks to multiple state incentives.

The U.S. hydrogen production tax credit (45V) has also been maintained as part of the recently passed One Big Beautiful Bill Act (OBBBA), providing a path to scale up production of low-carbon hydrogen and the reduction of hydrogen fuel price.

From an operational standpoint, FCEBs provide a seamless transition from diesel, compressed natural gas (CNG), and diesel-hybrid buses to zero-emission alternatives, without compromising performance. These hydrogen-powered buses offer the benefits of electric drivetrains - such as high torque, quiet operation, and regenerative braking – but with on-board power generation, ensuring consistent performance even on demanding routes and in challenging weather conditions.

In contrast, while diesel-hybrid buses are sometimes viewed as a transitional option, they offer only limited environmental benefits, increased system complexity, and an uncertain long-term role:

• More complicated systems: Diesel-hybrid buses combine diesel engines with electric motors, batteries, and regenerative braking systems, making them more complex than conventional buses
• Higher maintenance demands: Specialized components require trained technicians and more expensive maintenance, which can offset some of the fuel savings
• Not zero-emission: Diesel-hybrid buses still rely on diesel fuel, so they continue to emit nitrogen oxides, particulate matters, and greenhouse gases

As hybrid buses still depend on diesel, they fail to meet zero-emission regulations already in place in some states – and will fall even further out of compliance as the shift towards decarbonized transportation continues, regardless of changes in federal policy.

Moreover, diesel emissions are often concentrated in neighborhoods near bus depots and high-traffic corridors – typically in disadvantaged communities. Zero-emission buses (ZEB) help eliminate these localized health burdens, especially when powered by clean energy sources.

Operationally, there are other key considerations for transit agencies related to routes and duty cycles that can impact the economics of using diesel-hybrid buses as a stop gap solution:

• Benefits depend on route: Hybrid systems are most effective in urban stop-and-go conditions. On flat, highway routes, they may offer minimal advantage
• Performance degradation: As hybrid components age, both emissions reductions and fuel‑efficiency gains will decline
• Short service life risk: A diesel-hybrid bus bought today will reach its midlife at the same time transit agencies are likely to be mandated to electrify, leading to early retirement of vehicles or complex and costly retrofits
• Increasing cost: There has been limited recent investment in diesel-hybrid powertrains for buses due to the lack of long-term demand. As a result, the price of these buses has increased significantly recently, and only little improvement in powertrain performances is expected in the future
• Rising costs: The lack of long-term demand has stopped investment in diesel-hybrid powertrains, driving up purchase prices. Very little improvement in powertrain performance can be expected going forward
• Fewer funding opportunities: Even with a Low-No grant, diesel-hybrid buses are not eligible for matching incentives such as California’s Hybrid and Zero-Emission Truck and Bus Voucher Incentive Project (HVIP), VW settlements, and most Air District Board programs

The operational benefits and environmental imperatives leave no doubt: the shift to zero-emission transit is irreversible. Across North America, Europe, and Asia operators are abandoning internal‑combustion powertrains in favor of fully zero-emission fleets. While short‑term political cycles may sway regulations, the long‑term objective of 100% emission free transit remains unchanged.

This raises the question: Why invest in diesel hybrid buses – which have seen minimal powertrain improvements over the past five years – and risk being stranded for the next 12 years with obsolete technology, which will not meet current and future emission mandates?

In contrast, FCEBs offer a clear path forward: With bipartisan support as recently demonstrated by the hydrogen tax credits, the prospect of matching state funding, and proven operational advantages, they are the strongest candidates for the 2025 Low‑No grant cycle.

Public demand for clean, quiet buses is overwhelming and reverting to diesel‑based systems will do little to boost ridership as agencies work to recover from pandemic lows. Moreover, the health impacts of diesel emissions, especially in disadvantaged communities, underscore the urgent need for zero-emission solutions.

Our cities deserve cleaner air and a sustainable transit future.

For more information, resources, and support in submitting a Low-No grant application, click here.