The Capacity Tax of Idle Occupancy: Efficiency and Pricing in Public EV Infrastructure
Abstract: This paper examines the utilization efficiency of public electric vehicle (EV) infrastructure using transaction-level data from a major Swiss charging station provider. I document a pervasive friction in the market: 'idle occupancy' - the duration a vehicle remains connected after electricity delivery has ceased. To isolate behavioral idling from technical constraints, I develop a data-driven correction factor that accounts for the tapering of charging rates across different plug types. I find that idle time accounts for 54% of total connection duration at AC stations and 34% at DC stations. This behavior imposes a substantial 'capacity tax'. For my data, I estimate that the annualized charger investment costs attributable to unproductive occupancy amount to 1.88 mn CHF in the year 2021. Normalized by the total electricity delivered translates into around 1.7 CHF per kWh, which is several times higher than the prevailing electricity charging tariffs. To evaluate how prices can address these inefficiencies, I exploit a quasi-experimental setting where per minute charges are introduced after a 60 minute threshold. Using a bunching estimator, I find behavioral elasticities of 0.14 to 0.39 with respect to the marginal cost per minute for AC stations, while no such bunching is found for DC stations. The results suggests that most of the current fee structures fail to internalize the shadow price of the public charging infrastructure, and that implementing idle charging fees could temper the public outlays required to meet future EV infrastructure needs.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.