Summary

Access to affordable public charging is a salient factor for consumers switching to EVs, especially those without off-street parking. Meanwhile, the additional load that EV charging will place on electricity grids is of crucial concern to system operators seeking to balance growing demand with increasingly weather-dependent supply.

Demand flexibility has the potential to help to address both of these challenges: shifting EV charging away from peak periods and toward times when electricity is cheap and abundant, particularly when there is excess renewable generation. However, there is very little empirical evidence of the efficacy of smart public charging, and whether drivers respond to price or carbon signals outside of the convenience of their homes.

Centre for Net Zero has conducted the first large-scale randomised controlled trial, with 110,000 consumers in the UK, to evaluate the impact of a demand flexibility approach to public EV charging. This was delivered in partnership with the Octopus Electroverse platform, which ran “Plunge Pricing” events over 11 weeks that leveraged low wholesale prices during periods of high renewable supply to offer varying discounts to consumers.

Key findings

① EV drivers are highly responsive to price signals in public charging: a 40% reduction in price at the subset of participating chargers caused a 117% increase in demand across the network, while a 15% reduction led to a 30% increase. Overall, non-price signals to charge when the grid was "green" had no impact.

② Price signals create demand at discounted chargers during periods of high renewable generation, rather than displacing demand from other available charge points. We estimate that approximately half the increase in charging reflects drivers switching to the Electroverse app, and half reflects new induced charging demand.

③ Greater response from drivers in lower income areas and closer to charge points; these factors also appear to influence the impact of the green message.

④ Significant variation in response by geography and the time of day, showing when and where flexibility events occur matters.

⑤ Economic welfare gains from dynamic pricing for public EV charging, stemming from benefits for consumers and grid balancing. For consumers without access to home charging, it offers the potential to reduce EV running costs to levels comparable to - or below - those of petrol vehicles.