Difficult Depots: The infrastructure challenge behind zero-emission buses
By Julia Meek, Director of Bus – UK | 3-minute read
How to reduce risk and avoid common delivery pitfalls
Unlike fleet procurement, it brings together planning, highways, estates, energy networks, finance and legal processes – many of which sit outside traditional transport functions.
Across the sector, early projects have shown how easily infrastructure risks can surface late in delivery – affecting cost, timelines and operations.
In electrifying 122 depots across the world, including 73 in the UK, we’ve seen that successful schemes tend to share common characteristics:
- Early engagement with distribution network operators,
- Realistic phasing aligned to service requirements, and
- Procurement structures that reflect the long-term nature of the assets being created.
Our role is to work alongside bus operators and transport authorities to manage the infrastructure delivery process, from power and design considerations through to implementation, so that operational teams can focus on service planning and passenger outcomes.
Electrification challenges tend to follow a predictable sequence:
- Hurdle One: Establishing realistic power requirements
- Hurdle Two: Securing the grid connection
- Hurdle Three: Designing and building the infrastructure onsite
Hurdle One: Establishing realistic power requirements
Before a grid connection application or power procurement can begin, authorities need confidence in the scale and profile of a depot’s power demand. This is less straightforward than multiplying bus battery sizes by fleet numbers, as operational patterns drive infrastructure requirements. Authorities firstly need to determine:
- Expected fleet size over the contract period, not just at scheme launch
- Vehicle types and battery capacities likely to be introduced over time
- Dwell time in depot and the operational charging window
- Stand allocation and how vehicles cycle through the depot
- Interaction between charging strategy and electricity tariff structures
- The potential role of on-site generation or stationary storage, either immediately or in later phases
While some authorities commission this analysis separately, we use the expertise of our in-house Commercial Analytics team to incorporate it directly into our depot electrification delivery model. They analyse fleet data and test multiple configurations to establish the required connection capacity and charging strategy before infrastructure decisions are fixed.
This allows depot design to reflect long-term service plans whilst avoiding over-investment, under-capacity or future constraints that could limit fleet growth.
Hurdle Two: Securing the grid connection
Once power requirements are understood, the next step is securing the connection itself. This introduces new stakeholders for many authorities, particularly Distribution Network Operators (DNOs) and Independent Distribution Network Operators (iDNOs), alongside connection queues that can extend over several years.
At this stage, risk often arises from:
- Overpaying for a connection that is underutilised
- Misalignment between grid timelines and vehicle delivery schedules
- Delays linked to land agreements, planning consent or regulatory approvals
Zenobē manages this process as part of the infrastructure delivery role, coordinating directly with DNOs and iDNOs and aligning connection strategy with implementation plans.
Where appropriate, we facilitate iDNO asset adoption to reduce upfront capital requirements, allowing funding to remain focused on vehicles and passenger service improvements.
This approach enables electrification to progress in line with franchising and funding milestones, even in constrained network areas, while maintaining confidence in long-term programme delivery.
With greater control over fleet introduction and depot strategy, franchising authorities can co-ordinate vehicles, infrastructure and contracts together rather than addressing them separately through individual operators.
Early engagement allows risks to be understood before they become contractual.”
Hurdle Three: Designing and building the infrastructure onsite
Once power availability is confirmed, the challenge becomes integrating electrical infrastructure into an operational depot without disrupting services.
Most existing depots were not designed for electrification. Constrained layouts, shared access routes, heritage considerations and ageing utilities are common, and construction must usually take place while services continue to operate. Zenobē delivers the design and construction of depot infrastructure as a single coordinated programme.
Our engineering teams start with a whole‑site assessment: vehicle movements, current operating practices and planned fleet expansion. This avoids “regret cost” – expensive rework that happens when layouts, cable routes or charging strategies haven’t been considered early enough.
Example: At National Express’s Yardley Wood depot in Birmingham, grid constraints and a compact site ruled out conventional infrastructure upgrades. Zenobē installed a 667kWh battery storage system occupying just two parking spaces, charging from the grid during off-peak periods and discharging overnight to ensure a fully charged fleet each morning. The design was future-proofed to support fleet expansion and has since provided the blueprint for National Express’s wider electrification programme.
The final piece is making sure all of this can be built smoothly. During construction Zenobē coordinates contractors, installers and network works so that depots remain operational, sequencing works around service requirements and commissioning infrastructure in stages.
Case study: Nottingham City Transport - electrification within real-world constraints
In 2022, after securing £15.2m of ZEBRA funding, Nottingham City Transport began electrifying its historic Trent Bridge depot – a constrained site that had to remain operational throughout delivery.
The challenge
The heritage listed south building prevented visible external cabling and restricted structural alterations, while operational changes ruled out reverse parking options and reduced available layout space. In the north garage, a weak roof required bespoke structural solutions rather than standard installations.
On the power side, the depot needed two 1,800 kVA connections delivered via a 1.8 km engineered route crossing both a canal and a railway bridge – each adding technical and planning complexity.
The approach
Working closely with NCT and planning specialists, the design balanced heritage constraints with practicality. Space was created by reopening disused arches for charger installation and adopting a mixed charging layout suited to the site.
Zenobē peak power analysis aligned the charging strategy with available grid capacity and competitively procured connection works with an iDNO to reduce costs. Construction was phased to keep the depot fully operational, supported by close collaboration with NCT’s operational teams.
The outcome
Phase 1 was delivered on time and on budget, providing two 1,800 kVA connections over a 1.8 km route, enabling 30 electric buses and creating capacity for future expansion.
Even highly constrained, historic depots can be electrified successfully with the right blend of engineering, operations and commercial strategy.
Partnership: the key to reducing risk and avoiding common delivery pitfalls
Once power availability is confirmed, the challenge becomes integrating electrical infrastructure into an operational depot without disrupting services.
Most existing depots were not designed for electrification. Constrained layouts, shared access routes, heritage considerations and ageing utilities are common, and construction must usually take place while services continue to operate. Zenobē delivers the design and construction of depot infrastructure as a single coordinated programme.
Our engineering teams start with a whole‑site assessment: vehicle movements, current operating practices and planned fleet expansion. This avoids “regret cost” – expensive rework that happens when layouts, cable routes or charging strategies haven’t been considered early enough.
Example: At National Express’s Yardley Wood depot in Birmingham, grid constraints and a compact site ruled out conventional infrastructure upgrades. Zenobē installed a 667kWh battery storage system occupying just two parking spaces, charging from the grid during off-peak periods and discharging overnight to ensure a fully charged fleet each morning. The design was future-proofed to support fleet expansion and has since provided the blueprint for National Express’s wider electrification programme.
The final piece is making sure all of this can be built smoothly. During construction Zenobē coordinates contractors, installers and network works so that depots remain operational, sequencing works around service requirements and commissioning infrastructure in stages.
About the author
Julia Meek, Director of Bus – UK
Julia’s career has included a range of senior roles at mission-driven start-ups and scale-ups. Prior to joining Zenobē she was Head of Business Development for a UK social enterprise bus operator which included leading on public procurement bids, Chief of Staff at a microfinance organisation in China and co-founder of a social investment resource. She has an MBA from London Business School.
