A new report from the DOE describes the findings from six Smart Grid Investment Grant (SGIG) projects, in which electric utilities around the country evaluated operations and customer charging behaviors for home and public EV charging stations.
The report, Evaluating Electric Vehicle Charging Impacts and Customer Charging Behaviors, is intended to help utilities determine how long existing distribution infrastructure will remain sufficient to accommodate growing numbers of EVs (utilities are forecasting 400% growth in plug-in sales by 2023), and what type of capacity upgrades may be needed. It also examines how pricing and incentives can encourage consumers to charge during off-peak periods.
The six SGIG projects evaluated 270 public charging stations and 700 residential charging units. The study found that the vast majority of home charging participants charged their vehicles overnight during off-peak periods. Where offered, time-based rates were successful in encouraging greater off-peak charging. Public charging station usage was low, and primarily took place during business hours.
Length of charging sessions and the power required varied greatly. While the power demand to charge most vehicles was 3-6 kW, the load from one EV model (the Tesla Model S?) can be as much as 19 kW – more than the load for most large single-family homes.
Some utilities found interoperability problems between smart meters and residential charging stations. One company found that the two devices connected successfully only 50% of the time during load reduction events.