Flexing electric vehicle charging for socio-technical resilience: Distribution transformer headroom and locational value analyses

Wide deployment and passive integration of Electric Vehicles (EVs) will have implications on people’s needs, electricity system needs, and costs that could undermine future sustainability efforts. This study highlights the effectiveness of a tripartite tariff structure as a strategic mechanism for shifting electricity demand – especially EV charging – to off-peak periods during both daytime and nighttime hours. Unlike traditional night-only off-peak tariffs, the tripartite model offers a more equitable inclusive approach and helps manage aging urban infrastructure: supporting grid stability needs, achieving cost savings, and enabling greater consumer participation. An evaluation of 5,620 distribution substations of Northern Ireland electricity distribution system revealed that in the absence of flexible EV charging, significant grid reinforcement would be necessary: 66.7% of transformers would require upgrades with one EV per household, increasing to 77.9% with two EVs per household. However, when EV charging is made flexible through the tripartite tariff, upgrade requirements are notably reduced – to 51.9% and 63.0%, respectively. This flexibility results in substantial network upgrade deferrals, amounting to £57.3 million for the one-EV scenario and £59.8 million for the two-EV scenario, with the most significant benefits observed for higher-rated transformers. The findings underscore the need for region-specific strategies in planning EV charging flexibility, as variations in grid capacity, energy resource availability, and policy frameworks can influence outcomes. Additionally, the analysis suggests that transformer upgrades within the distribution system should target capacities of at least 500 kVA, where the impact of demand flexibility becomes more pronounced. Where infrastructure upgrades are necessary, cost-sharing should be equitable, ensuring that customers pay only their fair portion of the required investments.