Electric Car Charging Etiquette: Can I Unplug Your Car?

As Elon Musk was preparing for his cross-US journey in the new Tesla Model S, he might have been advised also to weigh in on the importance of charging station etiquette, a new UC Davis Institute of Transportation Studies study suggests. We all know how to pull into a line and sit in our cars waiting at a gasoline station, even if a car owner ahead of us goes into the convenience store for a drink, but what about at a charging station? Can we go into the store and ask an owner to unplug? How long is too long to keep your car attached if you cannot see if someone else is in line and might need the charger? A new social etiquette of charging is needed, researchers say, and an EV Emily Post has yet to emerge. Plugging in your car in a public station is a new behavior taking place in a social setting. US Davis ITS researchers Nicolette Caperello, Ken Kurani, and Jennifer TyreeHageman found that EV owners are unclear, “Even an available charger at an empty parking space can raise the question, ‘How long am I allowed to park and charge here?’ An occupied charger prompts questions too. ‘How long will they be there? Is that car fully charged? If it is, may I unplug it to plug mine in?” the authors wrote in their paper “Do you mind if I Plug-in My Car? How Etiquette Shapes PEV Driver’s vehicle Charging Behavior.” The authors note that as systems emerge to charge for the electricity more rules and norms may emerge. One driver surveyed said she would prefer to be able to make a reservation for public charging time. Others have left notes on their windshields giving instructions on what time would be acceptable to unplug their car, should a new user drive up.

As the number of EV users expands, congestion at public charging stations is inevitable. Social acceptance of electric car technology is growing, with plug-in electric vehicles reaching record sales in August 2013, climbing to 11,363 for the month. That represents a 141% gain from the previous year.

California continues to lead the nation, accounting for roughly 33% of EV sales. But more drivers means more congestion at charging stations. Another UC Davis survey found that 38% of California drivers polled reported that they were unable to charge at work at least once per week due to congestion at chargers. The study suggested that roughly four chargers are needed for every 10 vehicles when the electricity is free but only 1 charger per 10 cars might be necessary if the cost of charging was twice that of home electricity. In other words, as the study notes, “This usage pattern suggests that simply charging a small fee could encourage more efficient use of infrastructure,” by discouraging those who do not actually need to charge at work and encouraging them to charge at home.

But policy makers want to preserve the economic benefit of driving on electricity. To achieve that, charging prices have to be somewhere between the average home electricity price and the price of gasoline. UC Davis Researchers Michael A. Nicolas and Gil Tal calculated that the current breakeven with driving a plug-in Prius on gasoline would be 23 cents/kWh, way above household costs. While the vast majority of EV drivers would use a free charger daily, only 20% said indicated that they would use work based chargers if it were priced double that of home electricity, Nicolas and Tal found.

So, Elon Musk take note. Early adopters are advised to set a visible, polite example of exemplary charging behavior. As with any new technology, social acceptance will critical to success. As research shows, EV etiquette will be an important element to wide spread adoption.