Patterns of electric vehicle charging with time of use rates: Case studies in California and Portland

This paper presents patterns of electricity consumption for charging electric vehicles when customers can select flat or time of use pricing. The data consist of hourly charging profiles for two utilities whose customers were offered alternative rate schedules with rates different for weekdays and weekends as well as for seasons. The extent to which TOU customers´ daily load profiles differ from customers who opted for flat rates is presented for both weekdays and weekends. The on-peak and off-peak consumption for flat rate and TOU customers is compared to show that total consumption and timing of consumption varied by rate structure. Data show large differences in charging profiles for the varying rate structures. This paper discusses the different patterns observed between electric vehicle load and the rest of the residential load. Substitution and own-price elasticities are computed. In addition, issues related to self selection of pricing structures are discussed.