South Mimms Tesla Powerpack


  • Combining batteries and electric vehicles makes vehicle charging part of the solution to integrating more renewables without affecting drivers, unlocking vital flexibility to help build a smarter, more sustainable system.

    David Hill Commercial Director


At South Mimms Welcome Break Motorway Services on the outskirts of London, Open Energi have installed a 250kW/500kWh Powerpack alongside one of Tesla’s largest and busiest UK charging locations. The Supercharger site can charge up to 12 cars at one time, and since popular charging periods often coincide with peak periods of grid demand – between 4pm and 7pm, when electricity prices are at their highest – flexible solutions are needed to ease the strain on the local network and control electricity costs.

Integrating a Powerpack at the location has increased on-site energy capacity (from 800kVA to 1050kVA) and has meant that during peak periods, vehicles can charge from the battery instead of drawing power from the grid. This has kept costs down by avoiding peak tariff consumption and capping the maximum grid power. Throughout the remainder of the day, the Powerpack system charges from and discharges to the grid, earning revenue in return for helping National Grid to balance electricity supply and demand on a second-by-second basis.

Open Energi’s Dynamic Demand 2.0 platform continuously automates and optimises the Powerpack’s State of Charge (SoC) to meet drivers’ needs and manage site constraints whilst maximising value streams from peak price avoidance and firm frequency response (FFR).

This requires very careful operation. Requests to charge and discharge the Powerpack to meet EV demand and avoid peak prices must be managed according to site constraints and the capacity of the battery. The Powerpack needs enough stored energy to be able to discharge for the duration of a price or EV charging spike, while maintaining the availability to do FFR in accordance with any pre-contracted volumes required by National Grid. It needs to do so without overly increasing throughput and jeopardising the warranty. And at South Mimms, it needs to do so in the context of highly variable site demand. Open Energi has developed advanced SoC management and optimisation techniques to meet these requirements, demonstrating a significant uplift in value compared to manual scheduling or built-in controls.

The project at South Mimms Motorway Services has been operational since March 2017 and was one of the first of its kind worldwide. It provides a blueprint for the development of EV charging infrastructure globally, allowing vehicles to be charged quickly and efficiently without creating massive peaks in demand on the electricity grid.

Project Gallery

South Mimms Tesla Powerpack
South Mimms supercharger
Tesla South Mimms Supercharger and PowerPack


Energy Storage

Electric Vehicles


Balancing services

Peak price management

Constraint management

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