Confronting an electric vehicle-shaped “tragedy of the commons”

There are currently over 1 million electric vehicles (EVs) in the U.S. When these vehicles set off on their daily commute, they are consuming not gasoline but electricity, replenished through charging stations rather than gas stations. Accordingly, many workplaces have installed charging services for their employees. However, the presence of charging points does not guarantee their availability. In an intriguing quirk of resource-sharing at workplaces, early-birds often snag the limited charging spots and leave their cars plugged in all day, excluding other EV drivers from using the chargers.   

As the anticipated growth in EV use occurs, this seemingly trivial workplace skirmish will become ubiquitous: already, 38 percent of EV drivers in the United States experience congestion at charging stations at least once a week. This echoes the “tragedy of commons” phenomenon, where individuals – to the detriment of society – overconsume common resources that are not governed by social or formal rules. To avoid this issue hampering the efficient use and allocation of costly charging infrastructure, an effective system of rules for charger use should be established. The challenge now is determining what such an unwritten rulebook could look like.  

In a recent Journal of Industrial Ecology article, a multidisciplinary research team from Georgia Tech conducted a field experiment investigating techniques to manage the challenge of sharing workplace EV chargers. Across 12 months in 2014-2015, the researchers used charging app data to monitor employees’ charging behaviour across 105 charging stations at 25 large corporate campuses in the United States. By controlling for charger type and using high-frequency data, the team was able to determine the impact of two different incentives for limiting over-consumption. One incentive was price-based, and the other was non-price-based. Under the price-based incentive, EV-driving employees were subjected to price hikes from $0 to $1.00/ hour plus a $0.50 transaction fee after 4 hours’ charging. Under the non-price-based incentive, periodic messages were sent to employees urging them to ‘be considerate’ by unplugging their EV after sufficient charging – typically around 2 hours. This second incentive aimed to tap into the power of establishing “injunctive norms,” which signal what behaviours are or are not socially accepted. 

The researchers found that EV-driving employees responded equally well to both the price hikes and the periodic messaging, cutting down their time on the chargers by 15 percent and 19 percent respectively under each incentive. Interestingly, the analysis also revealed that managers responded differently than other employees when faced with the two incentives. Managers were more strongly influenced by the normative messaging incentive, which triggered a 25 percent reduction in their charger use, and did not significantly respond to the price incentive. The researchers suggest that this behaviour by managers – an influential group striving to set a good example – may help to explain the importance of social norms in the charging behaviour of other employees. 

This study provides key insights into what a successful rulebook to address the EV-charger “tragedy of the commons” might look like. To encourage better resource sharing, the researchers suggest that workplaces should implement incentive programs based both on pricing and on social norms. Targeting incentives at managers, especially social incentives, might be particularly influential. Of course, the effectiveness of different incentives will be workplace specific. Regardless, this study shows the power of small nudges to effect weighty change in our perception of shared resources. Extending this sense of interdependence and responsibility more broadly to issues beyond workplace EV-chargers could cause a huge leap in environmental action. After all, sharing – as they say – is caring, for people and for our planet.