By Adam Jiu | MIT News
Despite regional variability in climate, power sources, traffic congestion and wide variations in individual driving patterns, electric vehicles emit fewer greenhouse gases and cost drivers and vehicle fleet owners no more than comparable gas-powered vehicles in most parts of the United States, according to a new study by MIT researchers.
The team’s approach captures a number of key factors that contribute to regional and individual differences in life-cycle emissions and electric vehicle ownership costs, including meteorological data, travel distance and duration, and fuel prices.
To paint a more complete picture of emissions and consumption than was previously available, the researchers collected data from thousands of US zip codes and drilled down to the level of individual drivers within those locations. Their study considers time-averaged fuel prices so as not to be overly affected by price fluctuations at any one point in time. They finalized their analysis in late 2024 and early 2025.
Their results indicate that an individual’s driving behavior can be as important as regional factors such as the local electricity mix when it comes to the emissions savings of an electric vehicle, compared to a similar gas-powered vehicle. In most places, a battery-electric car reduces emissions by between 40 and 60 percent, with larger effects in urban areas.
They also found that a colder climate does not reduce overall emissions benefits as much as some media reports assume.
The researchers used this detailed analysis to update a public tool they had previously developed, carboncounter.comwhich enables individuals to compare the life-cycle emissions and total cost of ownership of almost any vehicle on the market. A new version of carboncounter.com is also being released today.
“Many statements are being thrown around, like electric vehicles don’t reduce emissions much in cold weather, and we wanted to systematically analyze these factors and simultaneously evaluate these statements against each other. Instead of simply asking, ‘Are EVs good?’, this paper helps answer ‘good for whom?’,” said Marcotti, Ph.D., and ETH Zurich researcher at MIT’s Institute for Data. Completed this research while a graduate student in Systems and Society (IDSS).
He is joined on the paper by senior author Jessica Transic, professor at IDSS. Research appeared today Environmental Research Letters.
A holistic approach
Miotti says that many previous studies that compare the emissions and costs of electric vehicles (EVs) with combustion-engine vehicles cover few factors, such as the amount of renewable energy on the grid and how gas prices affect affordability.
“To our knowledge, there have been few attempts so far that combine all these factors. But if someone wants to buy a car and have a better understanding of the factors that affect emissions and consumption, this holistic approach is important,” he adds.
The researchers focused on two types of EVs: battery-electric vehicles, which run solely on electricity, and plug-in hybrid electric vehicles, which also have a combustion engine that works in conjunction with batteries to optimize fuel economy.
The team expanded and improved a set of previously developed vehicle consumption and emissions models to include a wide variety of factors and data types.
For example, they refined an existing model that estimates energy use and gas mileage so that it can capture more nuances of local climate variability.
“But the real effort is not just to extend these different models, but to combine all these different data and make them work in a consistent way with the models,” Miotti said.
The team collected data on a variety of factors for each US ZIP code, such as typical drive cycles, traffic volumes, local gas and electricity prices, the makeup of the regional electricity mix, meteorological profiles and more. They used statistical methods to combine different types of data.
For example, the team used a probabilistic matching technique to combine data on how often people drive, taken from a nationwide travel survey, with more detailed GPS data that includes things like drivers’ acceleration patterns and the distance they typically drive each day of the week.
The researchers designed their analysis to focus on the spatial patterns of emissions and consumption based on US ZIP codes, while also considering the effects of each specific vehicle model’s size and features.
“At the end of the day, it’s the vehicle and fleet owners who make the vehicle purchase decisions. So, we wanted to make sure to consider their broader personal perspectives rather than just doing a region-by-region comparison,” Transic said.
Low emissions, comparable cost
Ultimately, their modeling framework revealed that they analyzed subjects equally in determining the emission-reduction potential of EVs compared to internal combustion vehicles.
EVs reduce emissions the most, in order of importance due to a cleaner mix of electricity, denser traffic, higher annual travel distances and a milder climate. In each area, emissions reductions increase for those who drive more often, drive larger vehicles, and are often stuck in traffic.
In colder areas like North Dakota, the fuel economy of battery-electric vehicles can drop as much as 50 percent on a particular winter night, but the impact on annual emissions benefits is minimal.
“We even did a sensitivity study to see if the range is reduced in very cold climates, and we found that, even in the most adverse conditions, EVs still reduce emissions substantially,” Miotti said.
On the cost side, the models show that, in most places across the United States, EVs are competitive with comparable combustion-engine vehicles in terms of lifetime ownership costs, even without clean car tax credits. And in areas where electricity is relatively affordable, battery-electric vehicles cost less than their plug-in hybrid or combustion-engine counterparts.
In the future, the researchers want to expand this analysis to include a temporal dimension, so the framework also considers how changes in vehicle, fuel, and electricity prices affect emissions and consumption over time.
“While we found that the electricity mix is a large driver of spatial variation in EV emissions savings, the electricity grid is decarbonizing everywhere. As that happens, emissions savings across space will become more homogeneous for EVs, but differences from one driver to another will persist,” Miotti said.
They could also use the framework to explore areas outside the United States or include data on hybrid-electric vehicles that can’t be plugged in.
This work was funded, in part, by the MIT Martin Family Society of Fellows for Sustainability.
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Reprinted with permission MIT News
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