Estimating the Marginal Emissions Impact of Electric Vehicle Adoption in the WECC region in 2030

Abstract

As the electric vehicle market rapidly grows, the prospect of a fully decarbonized light-duty vehicle fleet in the United States has drawn closer, with some states setting goals for new vehicle sales as early as 2035. Researchers that seek to quantify the emissions reductions of decarbonization policies enter into an active debate about the appropriate methodology for emissions rate calculations that adequately takes into account the complexity and grid dynamics of electrification. A major criticism of many studies estimating the emissions impact of electrification is that long-run grid investment effects of often overlooked. Currently, there exist no studies on transportation electrification that use a long-run emissions calculation. Here, we use the capacity expansion model GenX to calculate the long-run and short-run marginal emissions impact of electric vehicle adoption in the WECC system for the year 2030 under different demand response policies and cost scenarios. We find that short-run marginal emissions rate tend to significantly overestimate the emissions from EV adoption, as well as underestimate the magnitude of interventions like demand flexibility. This is largely due to the cleaner generation mix built as a response to additional demand, an effect overlooked in the short-run methodology. In addition, we show that the 8-hour overnight charging programs adopted by many utilities do not reduce emissions, while major emissions reductions result when 24-hour flexible charging is possible.