Assessment of Level 1 and Level 2 Electric Vehicle Charging Efficiency

Abstract

North American plug-in electric vehicle (EV) sales are projected to grow steadily in the next decade, and EVs are expected to become a significant portion of the vehicle feet. Widespread electrification of personal transport will require coordination between the electricity and transportation sectors. The coordination could include application of electric efficiency incentives that are commonly used in the energy sector for more efficient products, such as energy star appliances. The use of incentives for more efficient vehicles and charging equipment will facilitate a faster transition to this transformative technology. If EVs and electric vehicle supply equipment (EVSE) are found to be eligible for incentives, electric utilities could create programs that would accelerate EV deployment. The efficiency of 120-V Level 1 and 240-V Level 2 EVSE was compared with FleetCarma logger data collected from 1,008 Chevrolet Volt charging events. On average, Level 2 charging was 3% more efficient than Level 1 charging, but this percentage increased with shorter charge times. When less than 2 kW-h was drawn from the grid, Level 2 charging was 13% more efficient than Level 1. Although Level 2 charging was more efficient at all temperatures, the differences in efficiency were greater at high (above 708F) and low (less than 538F) temperatures. The greatest efficiency gains for Level 2 charging are expected at public charging locations, where charge times tend to be shorter and weather conditions more variable, as opposed to residential sites. Providing incentives for efficient EV charging infrastructure through utility and government programs will ensure optimal long-term investment in this new technology, reduce energy use, and facilitate more rapid uptake of EVs. EV charging infrastructure is eligible for federal funding under the Moving Ahead for Progress in the 21st Century Act. Thus, transportation agencies could include efficiency benchmarks as a requirement for project financing.