Recharging Loads on Electric Utilities due to Electric Vehicles

Depending on whether they recharge immediately after their final return home each day or much later at night, electric vehicles may increase existing peaks in electricity demand or fill in nighttime valleys when existing demand is low. These extremes are quantitatively projected and compared using travel data from the 1977 Nationwide Personal Transportation Study and a model of hour-by-hour operation at nearly 300 large US electric utilities. The travel data shows that final returns home are heavily concentrated around dinner time. Joint distributions of distances traveled and times of final return home are presented, and combined with a battery recharge profile to yield typical hourly recharging demands per electric vehicle. Similar hourly demands are developed for late-night recharging which might be induced by time-of-day electricity pricing. Operation of the utility model with these loads shows major differences in fuels used to generate recharge electricity and in the need for additional capacity under the different recharging load profiles.