Dynamics of workplace charging for plug-in electric vehicles: How much is needed and at what speed?

This paper presents workplace charging needs from two perspectives: the potential needs based on modelling and the needs based on survey results. These approaches both examine workplace needs from what people need to increase usage of the cars, and what workplace charging they will they actually use. The analysis reveals that for California driving patterns, chargers at the workplace can increase electric vehicle miles travelled (eVMT) by approximately 2%-10% for PHEVs and about 6%-9% for a 60-100 mile battery electric vehicle (BEV). The actual number of chargers used depends on the price charged. Both methods show that workplace charging will increase if charging is free versus a priced scenario with no extra benefit in terms of eVMT. The survey shows that 2 out of 10 vehicles will use workplace charging if it is priced between home electricity and gasoline on a cents per mile basis, while 8 out of 10 vehicles will use it if free on any given day. This corresponds to a 2-4 times increase in “needed” chargers depending on assumptions of how many cars one charger can serve per day. Also investigated was the speed of charging needed at work. Most charging of PHEVs can be accomplished with low power charging and 80% of BEV charging can be accomplished with low power. In general low power charging should comprise 80% or chargers, and charging price should be segmented by charging speed to encourage efficient use of high power chargers - reserving high power level 2 charging for those who need it such as some BEVs and utilizing low power chargers for PHEVs and low need BEVs.