Grid communicative “smart” charging of electric vehicles can provide significant benefits for maximizing the emission reductions provided by the large-scale use of these vehicles. While decentralized approaches to smart charging can be practical to implement in real systems, it is unclear whether these provide the same benefits for the electric grid as those identified by centralized approaches in the literature. This study compares the CO2 and NOx reduction benefits, and cost and grid capacity benefits, achieved by decentralized and centralized electric vehicle smart charging by modeling two different smart charging algorithms in battery electric vehicles and characterizing their effect on the operation and dispatch of electric grid resources and subsequently electric grid CO2 and NOx emissions. Decentralized approaches were found to provide the same CO2 emissions benefits and within 2% of the NOx emissions benefits achieved with centralized approaches, but only if the frequency of communication between vehicles and the electric grid is sufficiently high (less than 60 min). The difference in NOx emission is associated with the increased load variability caused by less frequent communication in decentralized smart charging resulting in higher power plant startup events. Finally, costs and grid capacity needs are increased without frequent grid communication.