The Cost of Staying Plugged In: Behavioral Responses at Idle Fee Thresholds in Public EV Charging
Abstract: This paper examines charging behaviour at public chargers using transaction-level data from a major Swiss public charging stations provider. I document tapering of charging rates within sessions and quantify idle charging (time spent occupying a charger after energy transfer ends). Idle charging is prevalent in particular at AC stations, averaging around one hour. This behaviour generates sizeable externalities valued up to 1 million CHF across observed sessions in 2021. I study how pricing affects inefficiencies by exploiting the existence of per-minute fees that operators impose after one hour. I employ a bunching estimator and find bunching elasticities of 0.14 to 0.39 with respect to the induced change in marginal costs. I also estimate tapering rates for different charger types. The half-life of the initial charging rate ranges from 35 minutes at faster AC chargers to 3.5 hours at slower AC chargers. The analysis underscores the importance of an efficient use of charging stations and potential inefficiencies can be addressed by appropriate pricing structures.Congestion Management for Electric Vehicle Charging Stations (with Jing Li)
Abstract: Congestion at electric vehicle (EV) charging stations has been a concern for drivers since the early days of the EV industry, and the concerns and issues grow as new EV sales continue to expand rapidly in many countries around the world. Using data from the charging industries in Germany and Switzerland from 2022 and 2023, we document two policy-relevant patterns in the data: (i) Congestion occurs throughout the EV charging networks in Germany and Switzerland. (ii) The distribution of charging session duration has a long right tail (right-skewed). (iii) Demand spills over from a congested charging station to neighboring ones. To evaluate the effectiveness of three congestion-management policies, we specify a model where drivers choose trip departure times, where to charge, and how long to charge: expanding the number of connectors, upgrading the electrical power, improving service quality (i.e reducing outages), and congestion pricing.