In an important real-world test of whether electric vehicles could play a bigger role in backing up the green power grid of the future, a group of San Francisco-area drivers showed that they were willing and even eager to adjust their charging times for the right financial incentives.

The small but sophisticated pilot test that took place over 18 months. During that time, BMW asked owners of its electric cars if they would be willing to delay recharging them by an hour on the company’s cue.

An app notified the owners when a delay was coming, and they could opt out if they needed to charge at that time.

“Eighteen months later, I can unequivocally state that participation was transparent, hassle-free and mind-numbingly dull to the point that I mostly forgot about it,” one participant, John Higham, wrote in a first person account of his experience for Inside EVs.

The trial led BMW and Pacific Gas & Electric (PG&E), the utility for Northern California, to suggest that if electric vehicles become as popular as expected, electric vehicle demand management could become a powerful tool for supporting grid flexibility.

“The overall lesson is we can use resources likes electric vehicles to help support the grid during times of peak use,” said Ari Vanrenen, a spokesman for PG&E.

Renewable energy experts have long held the theory that electric vehicles will play a momentous role in helping the electric grid be more flexible. EVs could be deployed to buffer uneven power generation of wind and solar. Owners might, for example, wait to charge their cars until the height of the day, when solar is most plentiful and cheapest. Or, they might delay their charging during peak hours in the early evening, when the grid is under the most stress.

As of now, customer sensitivity to prices is still an unknown quantity. While the BMW-PG&E partnership tested only whether customers would agree to delay their demand by an hour if given a financial incentive, it offered some concrete evidence that influencing customer behavior is possible.

How BMW Managed Demand

For the test, PG&E asked BMW to build a system that could remove 100 kilowatts of demand from the grid on short notice.

PG&E could make the call at a random time. Of particular interest to the utility was whether demand could eventually be decreased during peak load hours of 4 p.m. to 7 p.m., when solar power is waning for the day and demand on the grid ramps up.

BMW’s app would signal to customers that a one-hour delay was coming. If the car was connected to a charging station at that time, BMW could trigger the charging delay through software in the vehicle. Participants were paid $1,000 up front to participate in the study and $540 more depending on how many times their vehicle participated in the request for a one-hour delay.

If BMW could not meet the power reduction goal through delaying customer charging, it was encouraged to supply the necessary charging through its own battery storage center.

Throughout the 18-month test period, which ended in December 2016, customers were asked to delay 209 times. BMW was able to meet its obligations to reduce power about 90 percent of the time, however only 20 percent came from owner demand reduction and 80 percent come from BMW’s battery storage.   

The Challenge of Charging Times

While that seems far from conclusive, the results have to be seen in the context of a small pool of drivers whose vehicles would have to be connected to a charging station when the request came in. BMW found an average of only about seven of the nearly 100 cars involved were typically available to participate when a reduction request was announced. A lack of EV charging at work lowered the numbers.

If the time of the request came between 11 p.m. and 2 a.m., when cars were more likely to be plugged into their home charging stations, vehicle owners were much more likely to participate in the delay.

Since 93 percent of the participants stated that they liked the program and would be willing to participate in a similar program going forward, PG&E said it was eager to conduct a larger second phase. The California Energy Commission has given BMW a grant to lead that second phase with support from PG&E that has already begun.

As more and more EVs hit the road, programs like this have broad promise, the companies said.

“We can extrapolate to the future likely load reduction from plug-in vehicle drivers, as EV adoption increases,” said Rebecca Kiehne, a spokesman for BMW North America. “If we assume 20 percent of all existing EV owners enroll in a similar program, and behave similarly, a single future event might result in a load drop big enough to power approximately 58,000 homes in California.”