Electric vehicles (EVs) are becoming increasingly pervasive, and that will soon present an issue for the power grid. Smart charging programs, which shift EV charging to off-peak hours, offer a potential solution and potential rewards, such as compensation, for those who opt in.
“It’s a human behavior problem – people come home from work and charge their vehicles while everyone else is coming home and turning on their other devices. Electric vehicles could really exacerbate the peak of grid use,” Engineering Management and Systems Engineering (EMSE) Professor John Helveston explained.
Funded by The Alfred P. Sloan Foundation, Helveston and his EMSE PhD student, Pingfan Hu, collaborated with team members at UC Irvine, UC Davis, and RIT to measure EV owners’ willingness to participate in smart charging programs. Using a survey-based approach, the team set out to identify and quantify the incentives needed to encourage EV owners to join these programs.
The team deployed a conjoint survey, meaning respondents had to consider trade-offs when answering each question about whether or not they would choose to opt in to a smart charging program. They took an unconventional approach to identify survey respondents, placing paid ads on Facebook and Instagram targeted to keywords like “Tesla” and “electric vehicles,” inviting participants to share about their vehicles and preferences.
To ensure respondents were, in fact, EV owners, Helveston and Hu designed the survey to ask about respondents’ car makes and models, filtering out those whose vehicles were not electric.
“This approach worked really well for a hard-to-reach population,” Helveston explained.
To participate in smart charging programs, users must be willing to give up some degree of usability. As a result, it is costly to motivate individuals to participate. Financial incentives are not the only piece of the puzzle, though. Other features drive participation beyond compensation, including charging timing and whether grid operators can offer any battery percentage guarantees.
If not participating in a smart charging program, an EV owner may charge their vehicle to 100% battery immediately when returning home, placing increased pressure on the grid. But not every user needs or wants their EV to be charged fully every night, so long as they have enough battery to complete their upcoming trips. Grid operators in a given region may guarantee program participants that their EVs will be charged to 70% of battery capacity overnight.
Helveston and Hu realized that monetary and battery-related incentives are not linear and form a log-shaped curve. In other words, increasing the financial incentives to $20 is not comparable to increasing the battery-related guarantees by 20%.
“We find that incentive effects are not linear; small financial incentives create large early enrollment, satisfying the needs of EV adopters and enthusiasts. As incentives increase, though, we see diminishing returns: each additional increment in the incentive produces a smaller behavioral response. The remaining non-participants are also the hardest to convince, requiring much larger incentives,” Hu explained.
The unique nature of smart charging programs necessitated a unique approach to identifying and measuring the impact of these incentives. In traditional economic studies, a user or consumer’s willingness-to-pay is measured in dollars, but in this case, some grid operators may be able to attract new program participants without providing financial incentives. For some people, battery guarantees are enough to get them to sign up for the program.
The team also built a live online simulator to demonstrate how varying levels of monetary and battery-related incentives affect program enrollment.
“We designed it for utilities, grid operators, and policymakers who need to understand how different incentive portfolios influence enrollment. Users can benchmark the relative value of financial incentives versus battery State of Charge (SOC) and, more importantly, work backward from a target participation rate,” Hu said.
Helveston and Hu engaged with local grid operators in New York and California, and hope that their research will inform the design of dozens of smart-charging pilot programs across the country.
The team’s next step is to determine how much smart charging programs benefit the grid, thus informing the optimal approach for shifting the burden from the grid.