Tiny rewards can protect the grid from a surge in electric vehicles

A small financial reward can persuade many electric vehicle owners to charge their electric cars during off-peak nighttime hours – even when behavioural nudges fail to have the same effect.

That is the finding of a real-world trial that demonstrated how modest monetary incentives can ease the demand on power grids during peak usage hours. Such flexibility could be crucial as the number of people driving electric vehicles continues to grow worldwide.

“Offering an incentive to shift charging to the off-peak hours clearly reduced peak hours charging by 50 per cent, with a commensurate increase in off-peak hours charging,” says Blake Shaffer at the University of Calgary in Canada.

He and his colleagues enlisted 200 electric vehicle owners in Calgary and randomly split them into three groups. One received a financial incentive equivalent to 3.5 cents per kilowatt-hour of electricity use – roughly equivalent to $10 per month – if they charged their cars at home between 10 pm and 6 am, a period when electricity demand on the grid is usually lower. A second group only received a behavioural nudge consisting of information on the societal benefits of charging their electric cars during off-peak hours. A third group acted as a control, merely monitored to track baseline charging habits.

Surprisingly, the behavioural nudge strategy proved “completely ineffective”, says Shaffer. “Just asking them to do it out of the goodness of their heart didn’t show a strong enough effect.” But he suggests that more frequent reminders beyond the initial notice might have been more successful.

By comparison, the financial reward significantly shifted charging times – but only as long as people kept receiving money. Any reward cutoff led them to immediately revert to their old charging habits.

“The analysis does a convincing job of showing how a small financial incentive can really affect electric vehicle charging behaviour,” says Kenneth Gillingham at Yale University. Such incentives may have seemed like “easy money” because charging vehicles at night wasn’t too inconvenient, he says.

This is important because “many grids would need substantial upgrades” if growing numbers of electric vehicles are charging earlier in the evening, during peak demand hours, says Andrea La Nauze at Deakin University in Australia. Her own research has shown how financial incentives can encourage Australian electric car owners to charge during the day, when solar power is delivering maximum electricity to the grid.

Meanwhile, some utility companies – such as Con Edison and Orange & Rockland in New York – have already begun offering similar incentive programmes for off-peak charging.