First Bus uses depots for grid balancing

First Bus has begun using electric bus depots to support the UK electricity system by adjusting vehicle charging in response to grid balancing requirements.

The trial has started at the company’s Glasgow depot and is expected to extend to Great Yarmouth in Norfolk. It uses depot charging infrastructure as a controllable load, increasing electricity demand when surplus renewable output is available and reducing demand during periods of system pressure.

Optimo Energy is providing the optimisation platform, which schedules charging against grid signals while maintaining the battery state of charge required for daily bus operations. The arrangement gives depot charging infrastructure a more active role in electricity system management, with charging load adjusted to support balancing rather than simply minimised during peak periods.

The Glasgow site gives the trial a clear network context. Scotland produces large volumes of wind generation, but transmission constraints can limit the movement of power to demand centres further south. When generation exceeds available network capacity, renewable output may be curtailed. Flexible demand at large electrified depots can absorb surplus power where vehicle schedules and charging windows allow.

First Bus operates more than 1,400 zero-emission vehicles, representing around a quarter of its fleet. The company has also developed high-capacity electric depot infrastructure across the UK and has opened some of that capacity to third-party users through its First Charge offer. That creates a wider use case for depot assets, combining bus operations, external fleet charging, and grid flexibility from the same electrical infrastructure.

The trial sits alongside the wider move toward more active coordination between transmission, distribution, and flexible assets. MW Dispatch has gone live on the UK grid, allowing distribution-connected generators and batteries to help manage transmission constraints through coordinated dispatch between UK Power Networks and NESO. First Bus is approaching the same system pressure from the demand side, using large transport loads as adjustable capacity.

Depot electrification creates concentrated electrical demand at sites that were not originally planned around high-power charging. The load profile depends on charger ratings, vehicle duty cycles, connection capacity, smart charging controls, metering, communications, and the commercial structure for flexibility participation. Unmanaged charging can create new pressure on local networks. Managed charging can turn part of that load into a system resource.

Service availability remains the operating boundary. Bus batteries need to reach the correct charge level before vehicles leave the depot, and public transport timetables leave less flexibility than some industrial processes. The usable flexibility is therefore the charging load that can be shifted without affecting vehicle range, battery management, depot logistics, or daily operations.

The commercial case will depend on how flexibility revenues develop. Balancing mechanism participation, local flexibility services, constraint management, and other demand-side schemes each carry different requirements for metering, dispatch, verification, and settlement. Aggregated depot demand may become more valuable as electrified fleets grow, but the value depends on reliable data, automated controls, and operational certainty.

Electric fleet depots are becoming part of the power system rather than passive loads connected at the edge of it. Where connection capacity, charging controls, and operating schedules align, transport electrification can provide a flexible demand base for a grid managing more variable generation and heavier local constraints.