New research from the University of Bath reveals that reliability problems with electric buses could significantly undermine their economic viability and slow the transition away from diesel.
The study shows that while electric buses are cheaper to fuel and maintain than their diesel counterparts, they can spend considerably longer off the road due to parts shortages and the need for specialist repairs. This forces operators, particularly smaller and rural services, to maintain larger fleets with spare vehicles just to keep services running, dramatically increasing capital costs.
Using real-world data from UK bus operators, researchers applied a total cost of ownership model over a 20-year period and found that electric fleet size requirements increase by roughly 18 to 23% for every 10-percentage-point drop in availability compared to diesel buses.
At 85% availability, operators would need fleets around 30 to 40% larger than their daily operational needs, driving up capital costs significantly. The impact is most severe for smaller and rural operators, where each additional vehicle represents a larger share of the overall fleet and budget.
Lead author Jac McCluskey, from the Engineering and Physical Sciences Research Council Centre for Doctoral Training in Advanced Automotive Propulsion Systems at the University of Bath, said : ‘Electric buses can transform public transport and cut emissions dramatically but reliability is the missing piece.
‘Strengthening supply chains, parts availability and repair skills will help ensure these vehicles deliver affordable, dependable services everywhere, from big cities to rural towns.’
The research involved data from The Big Lemon, a bus operator that has been at the forefront of electric vehicle adoption since launching its first solar-powered electric bus in 2017.
Chief Executive Officer Tom Druitt said: ‘The Big Lemon has been at the forefront of the electric vehicle revolution since we launched our first solar powered electric bus in 2017, and we have gathered a huge amount of data since then on a wide variety of electric buses: new ones, second-hand ones and also retrofitted diesel buses, from both domestic and international manufacturers.
‘It has been a pleasure to work with the University of Bath to use this data to better understand the economics of electric bus procurement and share this experience with the wider industry.’
The study’s findings have significant implications for government funding. Due to a lag in availability data for newer electric buses, assessments rely mainly on earlier models. If availability hasn’t improved since 2020, operators may still need grants of up to 45% and ongoing support beyond 2040. However, if reliability keeps improving, required grants could fall to around 30 to 40%, ending entirely by 2032.
The Zero Emission Bus Regional Areas scheme offers grants covering up to 75% of the cost difference between electric and diesel buses, 75% of infrastructure costs and 50% of contingency expenses. These subsidies have helped accelerate adoption, with electric buses making up 60% of all UK bus registrations in 2023, a 76% increase from the previous year.
Professor Charlotte Deane, Executive Chair of EPSRC, said: ‘Electric buses are essential for reducing emissions and improving air quality. This EPSRC-funded research underlines the importance of ensuring the technology works for every community. By boosting reliability, we can make the switch quicker, fairer and more affordable.’
Falling battery prices and lower running costs are moving electric buses toward cost parity with diesel models, but the researchers argue that longer repair times and reduced availability could undermine their economic viability unless reliability improves.
The research was funded by UK Research and Innovation’s Engineering and Physical Sciences Research Council.
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