Researchers at the University of Michigan and Ford Motor Company have conducted a cradle-to-grave life cycle GHG assessment of model year 2020 ICEV, HEV, and BEV sedans, sports utility vehicles (SUVs), and pickup trucks in the United States. Light-duty vehicles, including sedans, SUVs, and pickup trucks, are currently responsible for 58% of US transportation sector emissions. Pickup trucks accounted for 14% of light-duty vehicle sales in the United States in 2020, and the market share of both pickups and SUVs has grown in recent years.

In an open-access paper in Environmental Research Letters, they show that the proportional emissions benefit of electrification is approximately independent of vehicle class.

For sedans, SUVs, and pickup trucks they found that HEVs and BEVs have approximately 28% and 64% lower cradle-to-grave life-cycle emissions, respectively, than ICEVs in the base case model. This results in a lifetime BEV over ICEV GHG emissions benefit of approximately 45 tonnes CO₂e for sedans, 56 tonnes CO₂e for SUVs, and 74 tonnes CO₂e for pickup trucks.

Though the percentage savings is approximately the same across vehicle classes, on average replacing an internal-combustion-engine sedan with a battery-electric sedan saves 45 metric tons of carbon dioxide equivalent, replacing an internal-combustion-engine SUV with a battery-electric SUV saves 56 metric tons of carbon dioxide equivalent, and replacing an internal-combustion-engine pickup with a battery-electric pickup saves 74 metric tons carbon dioxide equivalent over the lifetime of the vehicles.

—first author and Center for Sustainable Systems Research Specialist Max Woody

They also found that the benefits of electrification remain significant with increased battery size, reduced BEV lifetime, and across a variety of drive cycles and decarbonization scenarios.

Cumulative greenhouse gas emissions versus vehicle mileage for (a) internal combustion engine and battery electric sedans, SUVs, and pickup trucks, and (b) hybrid electric and battery electric sedans, SUVs, and pickup trucks. The lower and higher limits of each range are results for base and premium models, respectively. Woody et al.

… there is substantial variation in emissions based on where and when a vehicle is charged and operated, due to the impact of ambient temperature on fuel economy and the spatiotemporal variability in grid carbon intensity across the United States. Regionally, BEV pickup GHG emissions are 13%–118% of their ICEV counterparts and 14%–134% of their HEV counterparts across US counties. BEVs have lower GHG emissions than HEVs in 95%–96% of counties and lower GHG emissions than ICEVs in 98%–99% of counties. As consumers migrate from ICEVs and HEVs to BEVs, accounting for these spatiotemporal factors and the wide range of available vehicle classes is an important consideration for electric vehicle deployment, operation, policymaking, and planning.

—Woody et al.

This is an important study to inform and encourage climate action. Our research clearly shows substantial greenhouse gas emission reductions that can be achieved from transitioning to electrified powertrains across all vehicle classes.

This study expands upon previous studies that have focused on comparing battery-electric vehicle sedans to their internal-combustion-engine or hybrid counterparts. We report emissions for vehicle production, use, and end-of-life stages on a per-mile basis and over the total vehicle lifetime. In addition, we analyzed the regional variation in emissions considering differences in electricity grid mixes and ambient temperatures, and we also explored the effects of the rate of grid decarbonization on emission reduction.

—Greg Keoleian, a professor at the U-M School for Environment and Sustainability and director of the U-M Center for Sustainable Systems

Researchers looked at three different model year 2020 powertrain options—internal-combustion-engine vehicles, hybrid-electric vehicles, and battery-electric vehicles—for midsize sedans, midsize SUVs, and full-size pickup trucks, accounting for differences in fuel economy, annual mileage, vehicle production, and vehicle lifetime across vehicle classes.

The researchers found that switching an internal-combustion-engine vehicle to a battery-electric vehicle results in greater total tonnage of emissions reductions as the vehicle size increases, due to the greater fuel consumption of larger vehicles.

The researchers also found that battery-electric vehicles have larger greenhouse gas emissions in their manufacturing than internal-combustion-engine vehicles, due to battery production, but this impact is offset by savings in their operation. For battery-electric vehicles and internal-combustion-engine vehicles, the breakeven time is 1.2 to 1.3 years for sedans, 1.4 to 1.6 years for SUVs, and 1.3 years for pickup trucks, based on the average US grid and vehicle miles traveled.

Vehicle emissions vary across the country, as different temperatures and different drive cycles affect a vehicle’s fuel economy. For electric vehicles, the emissions intensity of the local electricity grid is also an important factor. The study developed maps to show the lifetime grams of carbon dioxide equivalent/mile for each powertrain (internal-combustion-engine vehicles, hybrid vehicles, and battery-electric vehicles) and vehicle type (sedan, SUV, and pickup truck) by county across the United States.

Researchers found that concerns about battery-electric vehicles having higher emissions than internal-combustion-engine vehicles or hybrids are largely unfounded, as battery-electric vehicles outperform hybrids in 95% to 96% of counties, while battery-electric vehicles outperform internal-combustion-engine vehicles in 98% to 99% of counties, even assuming only modest progress towards grid decarbonization.

Charging strategies can further reduce battery-electric vehicle greenhouse gas emissions. The study found that charging during the hours of the day with the lowest grid emissions intensity can reduce emissions by 11% on average.

This study was supported by Ford Motor Company through a Ford-University of Michigan Alliance Project Award.

Resources

• Maxwell Woody et al. (2022) “The role of pickup truck electrification in the decarbonization of light-duty vehicles” Environ. Res. Lett. 17 034031 doi: 10.1088/1748-9326/ac5142