First Bus launches UK trial using electric bus depots to support the grid (with Optimo Energy)

First Bus has launched a UK trial using electric bus depots to support the National Grid balancing mechanism by adjusting when vehicles are charged.

The project started at the operator’s Glasgow depot (at the time of conversion, 2021, it was the largest EV bus depot in the country) and will extend later this spring to Great Yarmouth in Norfolk. According to First Bus, this is the first time a UK bus operator has enrolled electric depots into the balancing mechanism managing electricity supply and demand shortly before delivery.

By shifting charging activity to periods of excess renewable generation and reducing demand during peak hours, the depots are intended to absorb renewable electricity that would otherwise be curtailed, particularly wind energy generated in Scotland.

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First Bus electric depots and grid flexibility

The trial is being delivered with Optimo Energy, whose platform manages charging schedules according to real-time grid signals while ensuring buses remain operationally available.

First Bus currently operates more than 1,400 zero-emission buses in the UK, around one quarter of its fleet, and plans to achieve a fully zero-emission commercial bus fleet by 2035. The company is also developing 20 electric depots across the country.

The trial will additionally assess the participation of bus depots in wider energy flexibility markets linked to charging infrastructure and electricity demand management.

First Bus also provides access to depot-based charging infrastructure for third-party fleets through its First Charge business, aiming at providing public charging possibility in up to 15 depots.

Isabel McAllister, Chief Sustainability Officer for First Bus, said: “Electric buses are already transforming public transport, but this trial shows that they have the ability to go even further: playing an active role in the UK’s energy system. We’ve built significant electric capacity across our depots, and the next step is using it more intelligently. By charging when the grid needs us to, we can help reduce wasted renewable energy, support system stability and improve the overall economics of electrification.”

Daniel Homoki-Farkas, CEO & co-founder of Optimo, said: “Electric fleets like First Bus’s represent a significant opportunity to support the UK’s transition to a more flexible energy system. By intelligently managing when vehicles charge, operators can respond to real-time grid needs, helping to reduce renewable energy curtailment, lower system costs and unlock new value from existing infrastructure. This trial is an important step in demonstrating how transport and energy can work more closely together.”