Scrapping a 2-year-old car for an EV still cuts carbon emissions by 44%, study finds

If you scrap a perfectly good car and switch to an electric vehicle, does that actually reduce greenhouse gas emissions — or make things worse?

A new study finds that even scrapping a gasoline-powered car just two years old and replacing it with an electric vehicle results in lower overall greenhouse gas emissions than keeping the old car.

The findings were published in Science, Vol. 393, No. 6811, by J. Elliott Campbell, a professor in the Department of Environmental Studies at the University of California, Santa Cruz, and Roland Geyer, a professor at the Bren School of Environmental Science and Management at the University of California, Santa Barbara. The research was funded by the National Science Foundation.

The question of when to replace a vehicle to minimize greenhouse gas emissions is not a new one.

Research teams in the United States and Canada in the early-to-mid 2000s concluded that drivers should keep their vehicles for 18 years before replacing them — in effect, for the car's entire useful life.

The reasoning was that manufacturing a new vehicle generates significant greenhouse gas emissions at the factory, meaning a switch to a slightly more fuel-efficient car would reach the end of its life before it could offset those production emissions.

If an existing vehicle emits 10 units of carbon per year, switching to a slightly cleaner model that saves only 5 units annually would never fully recover the 100 units of carbon emitted during production.

Those earlier calculations, however, focused only on marginally more fuel-efficient vehicles — not on switching to electric vehicles.

The research team therefore modeled three scenarios for a single SUV over a 16-year lifespan: driving it to the end of its life, scrapping it after 11 years and buying an electric vehicle, and scrapping it after just two years and buying an electric vehicle.

When the SUV was scrapped after two years, cumulative carbon emissions over the 16-year period were 44 percent lower than if the original vehicle had been kept. The upfront carbon cost of manufacturing the electric vehicle was paid back within three years of driving.

A vehicle's total greenhouse gas output breaks down into two parts: emissions from manufacturing and emissions from driving. The carbon released during production is fixed the moment the car rolls off the assembly line — it does not change whether the owner keeps driving it or scraps it today.

That means the only relevant comparison when deciding whether to switch is future emissions. The outcome hinges on whether the additional carbon needed to build a new electric vehicle is outweighed by the savings from running on electricity instead of gasoline.

Results varied widely depending on what vehicle was being replaced, however. Switching from a heavy fuel consumer to a low-energy electric vehicle cut carbon emissions by as much as 82 percent. Replacing an already fuel-efficient car with a large electric vehicle, on the other hand, actually increased emissions by as much as 77 percent.

For average mainstream vehicles, switching to an electric vehicle cut carbon emissions by 55 percent for sedans, 57 percent for SUVs and 55 percent for pickup trucks. For high-efficiency vehicles such as the Toyota Prius, the reductions were smaller: 56 percent for sedans, 34 percent for SUVs and 23 percent for trucks.

The smaller gains reflect the fact that fuel-efficient vehicles already produce relatively little carbon, leaving less room for improvement when switching to electric.

For the same reason, plug-in hybrid vehicles showed almost no benefit from switching, and in the sedan category emissions actually rose by 11 percent.

What about vehicles that are rarely driven?

Electric vehicles begin their lives with a carbon debt from the manufacturing process. To break even, a vehicle needs to be driven at least 7,054 kilometers per year for sedans, 6,837 kilometers for SUVs and 10,794 kilometers for trucks. Those thresholds are less than half the US average annual mileage of about 20,000 kilometers, meaning most vehicles — unless used only on weekends — will surpass the break-even point.

If the old vehicle is sold on the used-car market rather than scrapped, the calculation changes — because someone else will keep driving it. If the buyer previously walked or used public transit, the transaction adds new emissions that would not otherwise exist.

The research team calculated how many of the 100 people buying a used car would need to be first-time vehicle owners before the carbon savings from switching to an electric vehicle were entirely wiped out.

In regions powered largely by clean energy, the electric vehicle switch lost all environmental benefit once 81 of those 100 used-car buyers were first-time owners. In mixed-energy regions the threshold was 65, and in regions relying solely on fossil fuels it dropped to 42.

The researchers acknowledged, however, that at current electric vehicle subsidy levels, scrapping a relatively new car is not economically viable for most consumers.

The study also did not account for used-battery recycling. The global electric vehicle fleet has grown to about 40 million vehicles, but most are still relatively new and battery lifespans have proven longer than expected, so the volume of batteries being recovered remains small. As recycling infrastructure matures, the energy needed to mine raw materials will fall, making the environmental case for electric vehicles even stronger.

DOI: 10.1126/science.adv5441

J. Elliott Campbell, Roland Geyer, "The climate benefits of retiring a fully operational internal combustion engine vehicle." Science 393, 591–595 (2026).