•We quantify the potential of EVs to utilize fluctuating RES through optimized charging.•We use empirical driving data to model the behavior of key sociodemographic groups.•Optimized charging can double the utilization of RES compared to simple charging.•Trip information is more relevant than charger availability to utilize EV flexibility. Electric vehicles (EVs) are a new load type with considerable temporal flexibility. This work evaluates to what extent EV fleets (based on empirical driving profiles from two distinct sociodemographic groups) can cover their charging requirements by means of variable renewable generation (wind or solar-PV). For this purpose we formulate a mixed-integer optimization problem minimizing the amount of conventional generation employed. The results indicate that the usage of variable renewable generation can be more than doubled as compared to uncoordinated charging. Furthermore, we analyze how the utilization of renewable generation by EV fleets is affected through different portfolios of renewable generation sources, charging infrastructure specifications as well as a reduced optimization horizon.