University of California Institute of Transportation Studies

The rapid electrification of the transportation fleet in California raises important questions about the reliability, cost, and environmental implications for the electric grid. A crucial first element to understanding these implications is an accurate picture of the extent and timing of residential electricity use devoted to EVs. Although California is now home to over 650,000 electric vehicles (EVs), less than 5% of these vehicles are charged at home using a meter dedicated to EV use. This means that state policy has had to rely upon very incomplete data on residential charging use. This report summarizes the first phase of a project combining household electricity data and information on the adoption of electric vehicles over the span of four years. We propose a series of approaches for measuring the effects of EV adoption on electricity load in California. First, we measure load from the small subset of households that do have an EV-dedicated meter. Second, we estimate how consumption changes when households go from a standard residential electricity tariff to an EV-specific tariff. Finally, we suggest an approach for estimating the effect of EV ownership on electricity consumption in the average EV-owning household. We implement this approach using aggregated data, but future work should use household-level data to more effectively distinguish signal from noise in this analysis. Preliminary results show that households on EV-dedicated meters are using 0.35 kWh per hour from Pacific Gas and Electric (PGE); 0.38 kWh per hour from Southern California Edison; and 0.28 kWh per hour from San Diego Gas and Electric on EV charging. Households switching to EV rates without dedicated meters are using less electricity for EV charging: 0.30 kWh per hour in PGE. Our household approach applied to aggregated data is too noisy to be informative. These estimates should be viewed as evidence that more focused analysis with more detailed data would be of high value and likely necessary to produce rigorous analysis of the role EVs are playing in residential electricity consumption.