Hydrogen or Batteries? How Transit Agencies Are Choosing Their Zero-Emission Future

On June 12, 2026, the San Mateo County Transit District — better known as SamTrans — quietly made one of the more interesting bets in American transit. It announced that FASTECH and Bosch Rexroth would design and build a new hydrogen refueling station at its operations facility, clearing the way for a planned fuel-cell bus fleet. What made the decision striking wasn't the hydrogen piece by itself. It was the context: SamTrans also has roughly 108 New Flyer Xcelsior CHARGE NG battery-electric buses on order. In other words, one mid-sized California agency is deliberately building two zero-emission fleets, on two different fuels, at the same time.

That decision lands at a fraught moment. California Governor Gavin Newsom's May 2026 budget revision omitted $230 million in zero-emission transit capital, and the state Senate is pushing to restore it. The federal IIJA expires September 30, 2026, taking with it the largest ZEB funding program in US history. And every transit general manager in the country is being asked the same question SamTrans just answered with a shrug and a "both": hydrogen, batteries, or some of each?

The State Of The US Zero-Emission Bus Fleet

Before agencies can debate the mix, it helps to know what "the mix" actually looks like today. The picture is lopsided.

According to the CALSTART ZEB Tracker (mid-2024), there are about 7,028 full-size zero-emission buses either in service or on order across the United States. Of those:

• ~6,453 (91.8%) are battery-electric buses (BEBs)
• ~575 (8.2%) are hydrogen fuel-cell electric buses (FCEBs)

ZEBs still make up only about 4–5% of the country's ~70,000 transit buses, but new registrations have been growing 35–40% year-over-year since 2022. And the geography is even more concentrated than the technology: California alone accounts for 40–50% of every zero-emission bus in America, driven in part by the state's CARB Advanced Clean Transit (ACT) Rule — a 2019 mandate requiring every California transit agency to run a 100% zero-emission fleet by 2040, with ZEB-only purchases phasing in beginning 2023.

So the "hydrogen vs. batteries" debate is real, but it's not a coin flip. Batteries have won the volume war. Hydrogen is the specialty niche that refuses to go away — and, in the eyes of a growing number of planners, refuses to go away for good reasons.

Battery-Electric Buses: The Default Choice

BEBs are winning because, at least for the routes most agencies actually run, the math works.

What A Battery Bus Costs

A modern battery-electric transit bus runs roughly $750K–$1.1M to purchase, versus around $500K for a comparable diesel. But once the bus is in service, the operating economics flip. Electricity costs somewhere between $0.15 and $0.35 per mile — a fraction of diesel — and BEBs are mechanically simpler than combustion buses. NREL bus evaluations put 12-year maintenance costs around $280K, roughly 30% lower than diesel.

The catch is infrastructure and batteries. A full depot upgrade to support a large BEB fleet runs $5M to $20M or more, depending on size. And battery replacements, which typically come due after 8–12 years, add another $200K–$400K per bus. Utility interconnection is often the real bottleneck: a 400-bus depot may need 20–50 megawatts of new electrical capacity, and utility lead times for that kind of upgrade routinely stretch three to seven years.

Where Batteries Fall Short

Two limitations show up on real-world duty cycles. First, range: modern BEBs deliver 150–250 miles per charge, plenty for most urban runs but tight for long suburban or express routes. Second, cold weather: below about 20°F, range drops 20–40% as cabin heat and battery thermal management pull from the same pack. That's manageable in Los Angeles. It's a real operational headache in Chicago or Boston.

Charging strategy matters, too. Overnight depot charging takes 4–8 hours; on-route "opportunity charging" can top up a bus in 20–45 minutes but requires expensive high-power chargers at layover points.

Who's Going All-In On Batteries

Despite the constraints, the biggest US agencies have made batteries their default:

• LA Metro: 100% zero-emission by 2030 — the most aggressive target in the country
• NYC MTA: 100% zero-emission by 2040 (~5,800 buses)
• Chicago CTA: 100% zero-emission by 2040 (~1,900 buses)
• WMATA: 100% zero-emission by 2045 (~1,500 buses)

The supply chain reflects that bet. New Flyer's Xcelsior CHARGE, BYD, Gillig, and Lion Electric are all shipping battery buses at volume. There is, effectively, a working BEB market. As we've covered in electric buses and urban emissions, the environmental case is well-established once the grid keeps decarbonizing.

Hydrogen Fuel-Cell Buses: The Long-Range Specialist

Hydrogen is more expensive, more complicated, and — for a specific set of duty cycles — genuinely better.

The Cost Profile

An FCEB costs roughly $1.1M–$1.4M to purchase, meaningfully more than a BEB. Hydrogen fuel itself is the killer variable: green hydrogen currently runs $8–$16/kg, which at $10/kg translates to about $0.90–$1.20 per mile — several times the cost of running a BEB on electricity. A hydrogen refueling station costs $5M–$15M to build, though on a per-bus basis (spread across a fleet) that comes out to roughly $50K–$100K, comparable to a BEB depot's per-bus share.

The bottom line on lifecycle cost, per AC Transit's own 5x5/ZETBTA study and NREL evaluations:

FCEBs are, today, the most expensive way to move a transit passenger a mile. That's not a small point.

What Hydrogen Buys You

So why buy them at all? Because on the metrics that matter for certain routes, hydrogen wins clearly:

• Range: 300–450 miles per fill — essentially diesel parity
• Refueling: 10–20 minutes, versus hours for a battery bus
• Cold weather: fuel cells perform noticeably better than batteries below freezing
• Emissions at the tailpipe: water vapor, nothing else

For a suburban agency running 250-mile duty cycles on hilly terrain in a snowy climate, no battery bus on the market can do the job on a single charge without expensive mid-route charging infrastructure. A hydrogen bus can.

The Green Hydrogen Problem

There is, however, a large asterisk. Roughly 95% of hydrogen produced in the US today is "gray" — made from natural gas via steam methane reforming. Run an FCEB on gray hydrogen and, on a well-to-wheel basis, it's not really a zero-emission bus. It's a bus with the emissions moved upstream.

The DOE Hydrogen Shot target is $1/kg clean hydrogen by 2031, and California's ARCHES Hydrogen Hub — backed by a $12.6 billion DOE + ARCHES agreement signed in July 2024 — is the most concrete bet in the country on scaling green hydrogen production. Until that infrastructure exists at price and volume, the environmental case for FCEBs depends heavily on where you buy your hydrogen.

Permitting adds another layer of friction. Hydrogen refueling stations must meet NFPA 2 standards and handle 350–700 bar high-pressure storage, and the OEM field has narrowed significantly. New Flyer is now effectively the primary US FCEB bus manufacturer; Belgian builder Van Hool, which had been a notable supplier, filed for bankruptcy in April 2024 and is no longer an active market option.

The Agencies Actually Making These Calls

Aggregate statistics only tell you so much. The interesting story is in what specific agencies are doing on the ground.

AC Transit: The Hydrogen Pioneer

AC Transit in Oakland has been running fuel-cell buses since 1999 — longer than almost anyone in the world. Today its zero-emission fleet includes 30 FCEBs and 28 BEBs, about 58 buses total, or roughly 10% of the fleet. The agency has poured $294 million into its ZEB program, operates two hydrogen stations (a 9,000-gallon tank in Oakland, a 15,000-gallon tank in Emeryville), and has accumulated 6.5 million zero-emission miles while eliminating more than 15,025 metric tons of CO2.

Federal money has flowed in accordingly: $25.5M in FTA Low-No grants in 2023, another $15M in 2024, plus a $144M ARCHES grant in August 2024. AC Transit's own 5x5/ZETBTA study — one of the more rigorous side-by-side evaluations in the industry — concluded that BEBs perform best on short urban routes while FCEBs are better suited to long-range, high-duty-cycle routes, and that both technologies are needed in a complete zero-emission portfolio.

That "both" is doing a lot of work. It's also the reason so many agencies now look at this as a portfolio problem rather than a binary.

SunLine Transit: The Desert Test Case

Down in the Coachella Valley, SunLine Transit has been running FCEBs since 2000, making it another long-tenured hydrogen operator. SunLine's contribution to the industry's knowledge base is heat: fuel-cell buses hold up well in high-desert temperatures where battery packs would struggle with thermal management. That matters as the Southwest keeps getting hotter.

SamTrans: The Dual-Technology Bet

Which brings us back to SamTrans. Its June 2026 hydrogen-station announcement, paired with 108 battery buses on order, is essentially AC Transit's "both technologies are needed" conclusion translated into a procurement plan. The logic is straightforward: run BEBs on shorter urban and inner-suburban routes where overnight depot charging works, and use FCEBs for the longer suburban and peninsula routes where range and refueling speed matter more.

If SamTrans's approach becomes the template for mid-sized agencies, the national BEB/FCEB split may not stay at 92/8 forever.

2026 Rollouts To Watch

SamTrans is not alone in making near-term ZEB commitments. The brief's current editorial focus highlights three other agencies in the middle of their own transitions. San Diego MTS is actively expanding its battery-electric fleet as part of a broader sustainability plan, with new BEBs entering service on urban routes. Pace, the suburban-Chicago bus agency, is rolling out zero-emission buses into a service territory where winter temperatures make cold-weather performance a real operational factor — one that could put pressure on its BEB-heavy strategy. And Sun Metro in El Paso is advancing ZEB deployment in a smaller-market context, demonstrating that the transition isn't just a coastal, big-city story. Taken together, these three agencies represent the next tier of ZEB adoption: mid-sized, geographically diverse, and less cushioned by California grant money.

Federal Funding: A Cliff In September

None of this happens without money, and the money picture is genuinely uncertain.

The IIJA And Low-No Program

The Bipartisan Infrastructure Law (IIJA) allocated $5.625 billion to the FTA's Low- or No-Emission Vehicle Program across FY2022–2026 — roughly $1.0–1.1 billion per year. That is, by a wide margin, the largest federal ZEB investment in US history. It has underwritten a huge share of the BEB and FCEB purchases now on the streets or in production.

The IIJA expires September 30, 2026. Without reauthorization, the Low-No pipeline goes to zero. As we've discussed in our coverage of the transit fiscal cliff and IIJA deadline, the operating-side impact would be severe on its own. Layered on top of ZEB capital, it becomes a legitimate crisis for agencies mid-transition.

The BUILD America 250 Act

Congress is trying to respond. The BUILD America 250 Act, marked up by the House Transportation and Infrastructure Committee on May 21–22, 2026 by a 62–2 vote, would provide $87.6 billion for transit over FY2027–2031, with continuity for ZEB funding. It has not been enacted. We covered the full contours of that bill in our BUILD America 250 Act reauthorization explainer, and the short version is: it's the most credible current path to keeping Low-No alive, but nothing is guaranteed until a president signs it.

California Cross-Currents

Even in the state that leads the country on ZEB deployment, the political weather is mixed. Newsom's May 2026 budget revision omitted $230M in zero-emission transit capital; the state Senate is pushing to restore it. Meanwhile, the ARCHES Hydrogen Hub proceeds. The lesson for agencies is that state and federal ZEB funding, once assumed to be a steady flow, is now something to be actively defended year to year.

The Workforce Problem Nobody Talks About Enough

Buying a bus is the easy part. Training the people who maintain it is not.

Batteries: High Voltage, Growing Curriculum

BEB maintenance requires high-voltage safety training — modern buses run up to 800V DC — plus expertise in battery management systems and charging infrastructure. It's serious work, but community colleges and vocational programs are increasingly offering the relevant curriculum.

Hydrogen: A Dual Hazard

Hydrogen is harder. Technicians need training in high-pressure hydrogen handling (350–700 bar), fuel-cell stack maintenance, and — critically — the dual hazard of working around both compressed hydrogen and high-voltage electrical systems on the same vehicle. Outside California, formal training programs are scarce.

AC Transit's ZEBU: A National Model

AC Transit's Zero Emission Bus University (ZEBU) — run in partnership with Chabot College — is the country's first transit-collegiate ZEB training program. It has logged 26,798 training hours, operates in partnership with ATU Local 192 and Progress in Action, and received a $16M FTA grant to build a dedicated ZEBU facility. Apprentices earn credits toward an Associate of Science degree, and both federal and state agencies now recognize the program as a national model.

For any general manager building a ZEB plan, the ZEBU lesson is unavoidable: the workforce plan is part of the technology plan. Skip it, and you end up with expensive buses that spend too much time out of service.

So How Should An Agency Choose?

There's no universal answer, but there is a defensible framework. It looks something like this:

• Duty cycle — Urban routes under ~200 miles a day almost always favor BEBs. Long suburban, express, or intercity routes with limited layover time favor FCEBs.
• Climate — Persistent cold or extreme heat pushes toward hydrogen; mild climates make batteries an easier win.
• Grid capacity — If the local utility can't deliver 20–50 MW to your depot for years, hydrogen may be the faster path to fleet transition.
• Hydrogen supply — Is there realistic access to green hydrogen at a defensible price? If not, the emissions case weakens sharply.
• Workforce — Does the region have (or can it build) the training pipeline needed?
• Funding runway — Federal and state ZEB dollars are neither guaranteed nor infinite. Agencies that stack Low-No, state, and hub grants — as AC Transit has — get further faster.

The agencies making the most defensible decisions right now aren't the ones picking a side. They're the ones honestly matching technology to route, and building the workforce and infrastructure in parallel. As we discussed in the future of transit and in our broader look at transit and carbon reduction, the point isn't the drivetrain. The point is moving people cleanly, reliably, and affordably.

Conclusion

The next twelve months will tell us a lot. If Congress passes BUILD America 250 with ZEB continuity, the Low-No pipeline survives and the 35–40% annual growth in ZEB registrations likely holds. If it doesn't, agencies will face the IIJA cliff with contracts in flight and mandates like California's ACT Rule still on the books. Either way, the fundamental engineering picture won't change: batteries will remain the workhorse, hydrogen will remain the specialist, and the smartest agencies — like SamTrans, like AC Transit — will keep quietly running both. The zero-emission transition was never going to be a single technology winning. It was always going to be a portfolio, thoughtfully assembled, one route at a time.