Impact of Electric Tariffs on Medium- and Heavy-Duty Vehicle Charging Costs and Loads

This paper employs an economics-engineering model to simulate the impact of various electric tariff structures and rate levels on the charging economics of six hypothetical medium- and heavy-duty vehicle fleets, including their total bills and peak demand without managed charging as well as their opportunity to save money and lower their peak demand by managing their charging. It uses real fleet data from a set of fossil-fueled fleets as the basis for modeling the duty cycle of hypothetical electric fleets; employs heuristics for how an operator would respond to a price signal; models charging behavior in the context of several thousand rates described in the National Renewable Energy Laboratory’s Utility Rate Database; compares charging behavior depending on tariff features, including reliance on demand-based versus volumetric determinants, and the extent to which they are time-variant; and evaluates the potential for cost savings, peak demand mitigation, and the alignment between those outcomes. We find that managed charging can provide substantial cost savings for electric vehicle fleets while alleviating peak demand pressures on the grid. Among the tariff structures analyzed, those with time-of-use demand and volumetric components deliver the highest cost-saving opportunities compared with other tariffs, especially for fleets with adaptable charging schedules and significant daily mileage requirements. In contrast, tariffs with flat volumetric rates, or that do not include a demand component, may be straightforward but offer little incentive for cost optimization through load shifting.