Rethinking electric vehicle smart charging and greenhouse gas emissions: Renewable energy growth, fuel switching, and efficiency improvement

Global climate change and transportation electrification have propelled research on electric vehicles (EVs) and their impact on greenhouse gas (GHG) emissions. However, the effect of switching from uncontrolled to smart charging on EVs' GHG emissions has been a controversial topic in previous studies because several opposing effects of smart charging on emissions exist. We construct a stylized model and conduct an empirical analysis of three power systems to decompose the impact of smart charging on GHG emissions into three effects: renewable energy absorption, fossil fuel switching, and fossil fuel efficiency. We find that smart charging may increase GHG emissions when renewable energy penetration is low. However, as renewable energy grows, the joint impact of the three effects is reversed, enabling smart charging to reduce GHG emissions. Based on this analysis, we propose an adjusted smart charging mode to reduce GHG emissions significantly while slightly increasing electricity costs. Adjusted smart charging can reduce GHG emissions from EVs by 27.1% and 37.8% for two power system examples compared with uncontrolled charging.