Can new energy vehicles cut carbon emissions? Evidence from 201 Chinese cities

New energy vehicles (NEVs) are widely promoted for transport-sector decarbonization. However, empirical evidence on their emission-mitigation effects remains limited and prone to endogeneity issues of simultaneity and omitted variables. Here, we examine the causal impact of NEV sales on carbon emissions across 201 Chinese cities from 2010 to 2019. Specifically, we apply a Bartik-instrument-based two-stage least squares model integrated with a spatial autoregressive specification to address endogeneity and spatial autocorrelation. A case study (Pearl River Delta) further probes subnational drivers moderating the NEV-emissions relationship. Our results show that, on average, a 1% increase in NEV sales reduces city-level carbon emissions by 0.081%, with stronger emission-mitigation effects over time and in cities with supportive NEV policies or subway systems. In contrast, mitigation benefits weaken in colder climates and in cities with substantial power generation, manufacturing activities, or high-speed rail infrastructure. These findings support continued NEV promotion and inform context-specific decarbonization strategies.