Abstract:Plug-in hybrid electric vehicles (PHEVs), which run on both electricity from the grid and gasoline, are touted as providing some of the societal and environmental benefits of electric vehicles for a large portion of motorists' daily travel while also acting as a transitional technology toward fully electric vehicles. To test analysts' assumptions about how PHEV users will recharge their vehicles, the observed recharging behaviors of 40 households that participated in a PHEV demonstration in Northern California are reported. The recharging behavior across all households' last week of their 4-week PHEV trial period is summarized with regard to the time of day, frequency of plugging in, and electricity demand to recharge the vehicles. Although the means of the frequency distribution of plug-in events among demonstration households are similar to prior recharging assumptions made by analysts, the distributions are not symmetrical about the mean and there exists a large variation in both the average number of times households plugged in per day and the average energy per plug-in event. Further, there is no strong correspondence between the number of daily plug-in events and total daily electricity demand. The range of behaviors reported here supports the contention that the success of PHEVs in meeting energy and emission goals relies as much (or more) on PHEV users' recharging and driving behavior as on PHEV designs.