Green hydrogen is expected to play a crucial role in decarbonising hard-to-abate industries like steel and cement, as well as replacing fossil fuel-based hydrogen in existing applications. Heavy-duty trucking, shipping, and aviation are often regarded as hard-to-abate. What about city buses and coaches? In this case, the situation is different, as there may be alternative solutions that are not only more cost-effective but also easier to implement, especially in urban environments.
Buses are the most flexible and cost-efficient form of public transport, accounting for more than half of all public transport journeys in the EU. There are currently over 700,000 buses on EU roads, with an average age of nearly 13 years [1]. By comparison, there are more that 6.4 million of trucks in EU [2]. The vast majority of buses are powered by internal combustion engines. However, the demand for zero-emissions buses is steadily increasing, with 2019 marking a milestone year as 1,607 electric buses were sold, compared to only 594 in 2018. City buses are an ideal application for electric powertrains due to their driving cycle, which includes 2 to 6 stops per kilometer, resulting in an average speed range of 10-20 km/h. In fact, they are the first mode of transport where electrification is already making a significant societal and environmental impact. The term zero-emissions refers to tailpipe emissions and includes two technologies, battery electric buses (BEBs), and fuel cell electric buses (FCEBs). The former use batteries as energy carrier, while the latter use hydrogen, which is converted into electricity through a fuel cell. FCEBs can be viewed as BEBs with a fuel cell and fuel tanks added. While this makes them more complex, the advantage is that they rely on smaller batteries. However, due to energy losses, FCEBs require roughly three times as much electricity as BEBs, leading to three times higher operational costs. While there may be slight improvements in the future, a significant gap in operating costs will likely remain between the two zero-emissions technologies. The battery is the most expensive and range-critical component of a BEB, so future advancements in battery capacity and cost reductions will be crucial in determining the competitiveness of BEBs.
Electrification acceleration in city bus segment
In 2024, the number of new buses and coaches sold in EU reached 35,579 units, with 18.5% of them being electric [3]. To date, electrification has been limited to the city segment, where its market share surpassed 30% in 2023. When looking at growth rate over the last years, one can expected that 100% newly purchased city buses in EU can be all electric by 2027 [4]. Figure 1 illustrates the market share of new bus sales by powertrain technology [5]. The electric bus market is primarily dominated by BEBs, with only a total of 370 FCEB in operation across the EU as of January 1, 2023 [6].
Figure 1 New city bus sales – market share by powertrain.
Why electric?
The transport sector is the leading contributor to final energy consumption in the EU, accounting for 31% of the total in 2022. Within this sector, road transport represented 73.6% of energy consumption [7]. As a result, the transport sector is the second-largest source of greenhouse gas (GHG) emissions in the EU, responsible for 23.8% of emissions in 2022 [8]. In addition to climate change, other externalities from transport, such as noise and pollutant emissions, continue to contribute to premature deaths in the EU. However, it is important to note that vehicles meeting Euro 6 standards can be considered clean in terms of pollutant emissions. Furthermore, electrification makes public transport more attractive, which indirectly supports GHG reduction through a modal shift [9].
What makes electric buses so appealing, in particular in city traffic?
The key technology behind this is the electric machine, which enables energy-efficient propulsion with zero tailpipe emissions. To put this into perspective, in urban operations, an electric bus typically consumes less than 0.9 kWh/km for propulsion, while a comparable diesel bus consumes at least 4 kWh/km. Energy recovery is a crucial factor in achieving low consumption. Electric buses usually recover more than 40% of the energy used for propulsion in city conditions. Additionally, the energy consumption of an electric machine remains unaffected by heavy stop-and-go traffic, whereas a diesel engine experiences a significant increase in consumption under the same conditions. Finally, the noise difference between electric and diesel buses is most notable at lower speeds.
How to measure the environmental impact of electric buses?
The reduction of GHG emissions is a key driver of electrification. The use phase of electric buses accounts for the vast majority of emissions in a life cycle assessment (LCA) calculation [10]. Therefore, understanding how these emissions are benchmarked is essential. While the term ‘zero emissions’ specifically refers to the absence of exhaust gases and other pollutants from electric propulsion, the full picture is provided by well-to-wheel (WTW) emissions. These emissions encompass the entire lifecycle, including fuel production, processing, distribution, and consumption (see Figure 2).
Figure 2 Life cycle assessment – measuring the environmental and societal impact of electric buses.
Electric buses can be considered to have zero WTW GHG emissions if the electricity they use has a near-zero carbon intensity, meaning it is generated from renewable sources such as hydro, solar, or wind. Due to the high efficiency of electric propulsion, even BEBs powered by a coal-dominated electricity mix have WTW GHG emissions lower than those of diesel buses. Because direct electrification reduces final energy demand is considered as one of the key solutions for decarbonisation. Overall, energy efficiency improvements are considered the “first fuel” in the transition to clean energy, as they offer the most cost-effective options for reducing CO2 emissions [11]. As shown in Figure 3, the carbon intensity of EU electricity has been steadily decreasing, highlighting the growing GHG reduction benefits of direct electrification.
Figure 3 WTW emissions of a BEB (EU, 2023).
With the average EU electricity mix at 210 g CO2eq/kWh in 2023 [12], BEBs generate 76% fewer WTW GHG emissions compared to diesel buses [13]. In contrast, if hydrogen is produced using this energy mix, the GHG reduction is approximately 32%. Therefore, effective decarbonization through the hydrogen pathway relies on the use of green hydrogen. These differences arise because FCEBs have lower overall energy efficiency, primarily due to energy losses during electrolysis, compression, transportation, and the conversion of hydrogen into electricity. For example, a real-world comparison of BEBs and FCEBs in service Bolzano found that the TTW efficiency of FCEBs is between 2 and 2.45 times lower than that of BEBs [14]. As a result, FCEBs have a lower GHG emissions reduction potential and higher operating costs. Due to energy losses, it should be assumed that green hydrogen will be produced from surplus renewable energy. However, the challenge lies in the fact that building electrolysis plants designed to operate for only a limited amount of time may be economically questionable.
Public transport electrification challenges
The first challenge is the upfront cost – electric buses are considerably more expensive than their diesel counterparts, and this is unlikely to change in the near future. However, due to higher production volumes, technological advancements, and decreasing raw material costs, BEBs now offer larger battery capacities at similar price points. For example, the first electric buses in Luxembourg, introduced in 2017, had a nominal capacity of 76 kWh. By 2025, the maximum nominal capacity available on the market has increased to around 500 kWh. The key question is whether this is sufficient to support all public transport operations. The answer, for now, is yes, provided opportunity charging is used (typically via a pantograph at the terminus during layovers). This solution offers the advantage of virtually unlimited range with smaller, more affordable batteries. However, establishing such infrastructure requires careful planning and permits. With depot-only charging, some routes may still be unfeasible, especially in colder conditions where electric-only heating is required.
Looking ahead, it is likely that battery capacities available on the market will soon be sufficient to meet all the public transport needs in cities, thanks to advancements in battery technology driven by the passenger car industry. The open question in terms of total cost of ownership will revolve around the decision between depot charging and opportunity charging, especially as dynamic electricity tariffs become more widespread. While charging times of BEBs are decreasing thanks to technological improvements, they are still far from the quick refueling times typical for diesel buses, which only require a brief 5–10 minute refuel every two days.
Will FCEB be able to step in?
FCEBs offer longer range on a single charge and quick refueling times, positioning them as a potential solution, in particular for coaches. However, they are not yet viable due to the high costs involved in the production, transport, storage, distribution, and use of green hydrogen. A study conducted by a public transport operator in Warsaw highlighted the scale challenge [15]. To convert a single depot (with 300 buses) to FCEBs, 9,900 kg of hydrogen would be required daily, necessitating 33 trailers to deliver it each day. Additionally, storing such a large amount of hydrogen on-site has been identified as a significant safety concern. The analysis suggests that the challenge with hydrogen-powered buses lies not in the fuel cell itself, but in ensuring the availability of green hydrogen where it is needed. Another study by the Montpellier metropolitan authority, which planned to procure 51 FCEBs for deployment between 2023 and 2025, found that the primary barrier was the high annual operating costs, ultimately leading to the project’s cancellation (see Figure 4) [16].
Figure 4 Comparative Study of FCEBs vs. BEBs by the Montpellier Metropolitan Authority.
The majority of these costs are associated with electricity, as well as chemical and electrical engineering considerations. Additionally, challenges related to transportation, storage, and distribution arise from the inherent properties of hydrogen. For example, the low volumetric energy density of hydrogen makes its storage and transport particularly challenging [17]. All of these factors suggest that the availability of green hydrogen in the coming years will be very limited. To put it in perspective, global hydrogen demand reached 97 million tonnes in 2023 (dominated by the refining and chemical sectors), while low-carbon hydrogen production totaled less than 1 million tonnes [18]. Hence, the first goal is to decarbonise sectors that are using high-carbon hydrogen, followed by expanding into sectors where alternative solutions are either unavailable or more expensive. This process will take time, as the high costs and investment risks create a significant gap between ambition and implementation. For example, in 2023, only 7% of global capacity announcements were completed on schedule [19].
When discussing BEBs vs. FCEBs, we will assume a future scenario where affordable green hydrogen is abundant. When that happens, will city buses become a competitive application for hydrogen? Very unlikely. What about long-distance transport? That will depend on advancements in battery technology and the availability of charging infrastructure. Professor David Cebon from the University of Cambridge is quite straightforward on the matter: “Three times more on running costs, two times more on capital costs, you’d have to be insane to buy a hydrogen-powered truck, right?” [20]. On the other hand, two major players in the heavy-duty truck industry—Volvo and Daimler—are developing hydrogen-based solutions. Will they be able to compete with battery-electric solutions? Will one technology alone be enough enable zero-emission mobility? Only time will tell. One thing is clear— initiatives such as Luxembourg’s LuxHyVal [21] aiming at boosting hydrogen deployment across the entire value chain will be crucial for increasing the availability of green hydrogen.
References
[1] Fact sheet buses, ACEA, 2023 https://www.acea.auto/files/ACEA_fact_sheet_buses.pdf
[2] Fact sheet trucks, ACEA, 2023 https://www.acea.auto/files/ACEA_truck_fact_sheet.pdf
[3] New commercial vehicle registrations EU, ACEA, Press release 28 January 2025, https://www.acea.auto/files/Press_release_commercial_vehicle_registrations_2024.pdf
[4] Transport & Environment, Battery-electric is now the most popular for new city buses in the EU, https://www.transportenvironment.org/articles/battery-electric-is-now-the-top-powertrain-type-for-new-city-buses-in-the-eu
[5] Race to Zero: European Heavy Duty Vehicle Market Development, ICCT, Quarterly, https://theicct.org/publication/r2z-eu-hdv-market-development-quarterly-jan-sept-2024-dec24/
[6] Fuel cell bus projects in the spotlight: fleets, manufacturers, trends, Sustainable Bus, 2024, https://www.sustainable-bus.com/fuel-cell-bus/fuel-cell-bus-hydrogen/
[7] Final energy consumption in transport – detailed statistics, Eurostat, Data extracted in September 2024, https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Final_energy_consumption_in_transport_-_detailed_statistics
[8] Greenhouse gas emissions by country and sector, EU parliament, 2024, https://www.europarl.europa.eu/pdfs/news/expert/2018/3/story/20180301STO98928/20180301STO98928_en.pdf
[9] M. Seredynski, Pathways to reducing the negative impact of urban transport on climate change (2023), IET Smart Cities, vol. 5, 2023
[10] How LCA helps to understand the true environmental impact of electric buses https://www.volvobuses.com/no/news-stories/insights/lca-for-electric-buses.html
[11] IEA, energy efficiency, https://www.iea.org/energy-system/energy-efficiency-and-demand/energy-efficiency
[12] Greenhouse gas emission intensity of electricity generation, EU level, European Environment Agency,
https://www.eea.europa.eu/en/analysis/indicators/greenhouse-gas-emission-intensity-of-1/greenhouse-gas-emission-intensity-of-electricity-generation-eu-level
[13] UITP Bus Tender Structure Report 3.1. Annex IV, Default Values SORT 2 Compared to Diesel Euro VI
[14] A. Poggio, J. Balest, A. Zubaryeva, W. Sparber, Monitored data and social perceptions analysis of battery electric and hydrogen fuelled buses in urban and suburban areas, Journal of Energy Storage, vol. 72, 2023
[15] Duża zajezdnia z autobusami zasilanymi wodorem – problemy skali, Komisja Taboru Autobusowego IGKM, Kielce, Poland, 11.10.2022
[16] Pourquoi la Métropole de Montpellier renonce aux bus à hydrogène, https://objectif-languedoc-roussillon.latribune.fr/politique/politiques-publiques/2022-01-06/pourquoi-la-metropole-de-montpellier-renonce-aux-bus-a-hydrogene-899735.html?s=03
[17] Q. Hassan, et al., Hydrogen as an energy carrier: properties, storage methods, challenges, and future implications, Environment Systems and Decisions, vol. 44, 2024
[18] IEA, hydrogen, https://www.iea.org/energy-system/low-emission-fuels/hydrogen
[19] A. Odenweller, F. Ueckerdt, The green hydrogen ambition and implementation gap, Nature Energy, vol 10, 2025
[20] “The gap will widen”, says prof. David Cebon on electric vs hydrogen, https://www.einride.tech/insights/prof-david-cebon-on-electric-vs-hydrogen-the-gap-will-widen
[21] Luxembourg Hydrogen Valley, https://luxhyval.eu/