Behavioral Science in Action: The ChargeMinder Mobile App for Cleaner EV Charging
By Laura Libby, Linda Chang, and Monica Van
In Toyota’s broad carbon reduction strategy, Plug-In Hybrid Vehicles (PHEVs) and Battery Electric Vehicles (BEVs) play a key role. However, simply owning a PHEV or BEV is not enough; how people charge electric vehicles affects overall well-to-wheel emissions. For example, PHEVs must be charged regularly to minimize miles driven on fuel, and vehicles should ideally be charged when the power grid is using more clean, renewable energy sources. These are examples of opportunities where drivers can decrease their carbon emissions with small shifts in their behaviors.
Research in behavioral science shows that modest, targeted interventions can significantly impact people’s decisions and actions. Compared to other behavior change mechanisms, such as public charging infrastructure initiatives and consumer financial incentives, behavioral interventions are inexpensive and scalable. At TRI, the Human-Centered AI (HCAI) team has started developing and testing behavioral interventions to shift charging habits towards sustainability goals.
Introducing ChargeMinder
To apply behavioral science insights to key charging scenarios, we built ChargeMinder, a research prototype mobile app for intervention deployment and evaluation.
ChargeMinder integrates more than a dozen interventions that are based on well-replicated findings from behavioral science research, tailored for specific charging behavior change goals. These interventions are surfaced in in-app features and through mobile push notifications.
Example intervention: Just-In-Time Charging Reminders
One ChargeMinder intervention feature is “Just-In-Time Charging Reminders.” Research has shown that prompts delivered at the moment of decision are up to 50% more effective for shifting behaviors, compared to other points in time (Forman et al., 2019, Gustafson et al., 2014, Levin et al., 2019, Van Dantzig et al., 2018). In other words, interventions should be delivered at the right place and at the right time.
To apply this insight to the charging context, we built a push notification system that reminds users to plug in their vehicles at user-defined charging locations at the right time of day to elicit the target charging behavior.
Other ChargeMinder intervention features include:
- Implementation intentions for a self-selected charging goal (Milkman et al., 2011; Nickerson & Rogers, 2010)
- Behavioral feedback through streaks and graphs (Silverman & Barasch, 2023)
- Positive reinforcement with encouraging messages (Skinner, 1963)
- Engaging educational content that leverages memory science to enhance curiosity and learning (Kirgios et al., 2025; Rowland, 2014)
Private, personalized user data
The ChargeMinder platform can also securely and anonymously capture and surface user data from multiple sources, including vehicle telemetry, app interactions, and charging locations. With this data, we can provide a personalized intervention experience, monitor app usage, and conduct advanced data analysis while preserving user privacy.
The impact
We measured the impact of ChargeMinder on real-world charging behaviors in two public pilot tests, one in the US focused on PHEV charging and the other in Japan focused on daytime EV charging from solar power. Here’s what we found:
- In the US, PHEV drivers who received ChargeMinder interventions increased charging by 10% compared to a control group who did not.
- Interventions increased U.S. PHEV drivers’ satisfaction with their vehicles by 16 percentage points, bringing satisfaction to 100%.
- In Japan, where we modified the app to emphasize charging during peak solar hours, EV drivers shifted behavior by 59%, adding nearly 30 minutes of daily daytime charging per vehicle.
Bridging the intention-action gap
Why does ChargeMinder have such a strong effect on charging habits?
To answer this question, we ran a survey of 1200 PHEV drivers in the US and 2400 EV (PHEV and BEV) drivers in Japan. We found that the majority want to optimize their charging and care about reducing their environmental impact. However, our behavioral and self-report data also show that people do not always behave according to their intentions and values. In behavioral science, this discrepancy is known as an intention-action gap (Ajzen, 1985).
Intention-action gaps often exist due to cognitive barriers. For instance, a PHEV driver might plan to charge every day, but sometimes they are busy and forget to charge. An EV driver might prefer to charge from renewable energy sources, but they aren’t aware that solar energy is available on their local power grid during the daytime. Before building our behavior change app, we identified these and other key cognitive barriers to greener charging and designed ChargeMinder’s interventions to counteract them.
The behavioral science in ChargeMinder creates a scaffolding between EV drivers’ intentions and actions. The interventions bring awareness and attention to greener charging choices, provide behavioral transparency, and reduce behavioral noise. Finally, by empowering people to match their intentions and actions, ChargeMinder taps into people’s internal motivational system, so that the charging experience is a reward unto itself.
How we tested ChargeMinder
Both pilot studies were designed as randomized controlled trials (RCTs) following a similar structure. ChargeMinder was downloaded by approximately 100 paid research volunteers in each market, drawn from representative samples of PHEV or BEV owners driving twelve different vehicle brands.
Users were randomly assigned to either the Treatment group or the Control group. Both groups used ChargeMinder for five weeks. In the first week, neither group received interventions, allowing us to measure users’ baseline charging behavior. For the remaining four weeks, only the Treatment group received intervention features designed to change behavior.
At the end of each pilot, app features and data collection were disabled, and users were allowed to remove ChargeMinder from their devices.
Why it matters
Our ChargeMinder pilot results demonstrate the power of modest, low-cost interventions to shift real-world EV charging towards carbon neutrality goals. Additionally, this work emphasizes the importance of incorporating behavior change as a key part of decarbonization strategy. We need to build technologies that account for how people think, feel, and behave in order to bridge the gap between human behavior and carbon reduction.
What’s next
We are working to extend our ChargeMinder research program, expanding to more personalized, data-driven, and dynamic interventions. In the future, in collaboration with the Carbon Neutral Center at Toyota Motor Corporation, we will test ChargeMinder in new audiences and new scenarios, supported by our flexible behavior change platform architecture. In the long term, what we learn with ChargeMinder will help Toyota make EV charging even more aligned with Toyota’s global carbon neutrality strategy.
If you are heading to Climate Week NYC 2025, Toyota will be hosting a main stage event with The Nest Climate Campus on September 24! Get insights from Toyota leadership, TRI researchers, and industry voices, focusing on carbon reduction solutions, not just on what’s new but also on what’s overlooked.
Register to attend here: https://www.thenestclimatecampus.com/register
References
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Kirgios, E. L., Athey, S., Duckworth, A. L., Karlan, D., Luca, M., Milkman, K. L., & Offer-Westort, M. (2025). Does Q&A Boost Engagement? Health Messaging Experiments in the United States and Ghana. Management Science.
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