Public EV Charging Choices: How Users Trade Off Time, Price, and Renewable Energy

Abstract

The carbon intensity of electric-vehicle (EV) charging varies over time and place, yet EV charging recommender systems and eco-routing interfaces rarely make this variation actionable for drivers. We investigate how renewable-energy information interacts with two attributes that routinely shape public-charging decisions: travel time and price. Fifty car users completed a within-subjects stated-choice study with three navigation-interface variants, and 10 EV drivers participated in semi-structured interviews. Across the three variants, the share choosing the slower option was 38%, 42%, and 66%, respectively. A paired-sample analysis found that choices differed across variants (Cochran's Q(2) = 11.47, p = .003). When the time-price trade-off was held constant, adding a renewable-energy label increased selection of the slower station from 38% to 66% (exact McNemar test, Holm-adjusted p = .004). Interviews nevertheless showed that renewable energy was usually a secondary consideration: participants evaluated it through situational constraints such as urgency, charging cost, traffic, charger availability, and familiarity with locations. We derive a constraint-first design rationale for renewable-energy-aware charging recommendations: filter options using context-sensitive time and cost constraints, disclose the renewable-energy signal and its uncertainty, and preserve user control rather than relying on a green default alone. Together, the results provide an empirical baseline for research on green charging recommendations, while characterizing stated choices in a small exploratory sample rather than real-world charging behavior.