A new study led by researchers at the University of California, Santa Cruz, has delivered a striking conclusion about the climate impact of electric vehicles: from a carbon-emissions perspective, replacing a fully functional gasoline-powered car with a battery electric vehicle can be better for the planet than continuing to drive the older vehicle—even when the gas car is brand new. The research challenges the widespread assumption that keeping an existing car on the road is always the most environmentally responsible choice because manufacturing a replacement requires substantial energy and raw materials.
Published in Science, the study examined the climate trade-offs involved in retiring internal combustion engine vehicles before the end of their expected service life. Researchers Elliott Campbell of UC Santa Cruz and Roland Geyer of the University of California, Santa Barbara, compared the lifetime emissions associated with gasoline-powered vehicles, conventional hybrids, plug-in hybrids and battery electric vehicles. Their analysis considered the emissions produced during manufacturing, fuel production, electricity generation, vehicle operation and eventual replacement.
The central question was not simply whether electric vehicles produce fewer emissions than gasoline cars. Earlier research has already established that battery electric vehicles generally have a lower lifetime carbon footprint. Instead, the researchers wanted to determine when the emissions avoided by driving an electric vehicle become large enough to compensate for the emissions generated during its manufacture. Producing an EV typically creates a larger initial carbon burden than producing a comparable gasoline vehicle, largely because of battery production. The study found, however, that this disadvantage is usually overcome after approximately three years of driving.
To reach their conclusions, the researchers modeled more than 400 gasoline and battery electric vehicle configurations. Their calculations accounted for differences in vehicle size, fuel economy, annual mileage, battery capacity, manufacturing emissions and the carbon intensity of regional electricity grids. They then compared multiple replacement schedules, including keeping a gasoline vehicle in service for approximately 16 years and replacing it with an EV after only one, three, five or more years.
The largest climate benefit occurred in the most aggressive replacement scenario. Retiring a gasoline-powered vehicle after its first year and replacing it with a battery electric model produced an estimated 58 percent reduction in carbon emissions over a 16-year period. Although manufacturing the EV caused an immediate increase in emissions, the lower emissions from operating the electric vehicle rapidly reversed that initial impact. Once the break-even point was reached, every additional mile driven with electricity increased the overall climate advantage.
The explanation lies in the fundamental difference between the two powertrains. A conventional internal combustion engine converts chemical energy in gasoline into motion by burning fuel, but most of the energy is lost as heat. According to the researchers, only about 20 percent of the energy contained in gasoline is ultimately used to move the vehicle. Electric motors are substantially more efficient, converting a much larger share of stored electrical energy into motion. Even when electricity is generated partly from fossil fuels, this efficiency advantage often gives EVs a lower operating carbon footprint.
The benefits are not identical everywhere or for every vehicle. Electricity generated primarily from coal produces more emissions than electricity supplied by renewable sources, nuclear power or lower-carbon natural gas. In regions with exceptionally carbon-intensive grids, the manufacturing emissions of a new EV can take longer to offset. The researchers found that owners of highly efficient conventional hybrid vehicles should think carefully before replacing them early if their electricity grid produces more than 970 pounds of carbon dioxide per megawatt-hour, placing it among the most polluting grids in the United States.
Annual driving distance also matters. A vehicle that is driven only occasionally generates fewer operating emissions, reducing the speed at which an EV can recover its manufacturing footprint. The study identified very low-mileage gasoline vehicles as exceptions to the general pattern. Replacing a car driven less than about 7,054 kilometers per year, an SUV driven less than 6,837 kilometers, or a truck driven less than 10,794 kilometers may not produce a net carbon benefit before the vehicle’s normal retirement age. Plug-in hybrids also produced mixed results because their smaller batteries and ability to run on gasoline can make some models relatively efficient.
The researchers say the findings have direct implications for public policy. Vehicle “scrap-and-replace” programs, which provide financial support to people who trade in older, high-emitting vehicles, could produce greater climate benefits if they were expanded to include a broader range of operational gasoline cars. Such programs could also make EV ownership more accessible to households that cannot afford the higher upfront cost of a new electric vehicle. As electricity grids shift toward renewable energy and battery recycling becomes more widespread, the climate advantage of replacing gasoline vehicles with EVs is expected to increase. The study’s broader message is that delaying the transition is not always the greener choice: in most real-world situations, moving to an electric vehicle sooner can reduce transportation emissions more effectively than waiting for a gasoline car to reach the end of its life.
Subject of Research: Climate benefits and carbon-emissions trade-offs of replacing operational internal combustion engine vehicles with battery electric vehicles
Article Title: The climate benefits of retiring a fully operational internal combustion engine vehicle
News Publication Date: 6-Aug-2026
Web References: https://www.epa.gov/egrid/power-profiler#/ ; https://ww2.arb.ca.gov/our-work/programs/clean-cars-4-all/about
References: Science, DOI: 10.1126/science.adv5441
Image Credits: Allison Arteaga Soergel/UC Santa Cruz
Keywords: Electric vehicles, battery electric vehicles, climate change mitigation, carbon emissions, internal combustion engines, transportation emissions, vehicle replacement, life-cycle assessment, hybrid vehicles, clean energy
