With all the limits on electric vehicles—battery life, cost, the availability of charging stations—you might expect that at most 50 percent of the vehicles on U.S. roads could be replaced by more-sustainable cars.
Buckle up: It’s 87 percent, MIT reckons, in a study published Monday in the journal Nature Energy. Such a proportion, if it were the case today, would lead to a 60 percent reduction in total U.S. gasoline consumption and a 30 percent decrease in the 1.8 billion metric tons of greenhouse gas emissions emitted by all American transportation in 2014.1 Transport represents 26 percent of America’s total greenhouse gas emissions.
But it's an interesting one. The findings represent a “technical potential” that shows how many households could start living more sustainably now, said Professor Jessika Trancik, who led the study. For instance, in a two-car household, having one electric car and one conventional vehicle could meet drivers’ needs across the country and significantly increase the number of electric vehicles on the road.
The researchers found that more affordable electric vehicles, such as the Ford Focus Electric and the Nissan Leaf, could meet our energy and affordability needs if people recharged their cars just once daily, either overnight at home or during the day at work. Then the scarcity of public charging stations wouldn't be as pressing. And although electric vehicles’ sticker prices are higher, the researchers concluded that their operating costs would be lower than for conventional cars. This would make the overall costs comparable.
The study noted that rural areas had a slightly smaller adoptive potential than urban areas but found similar potential across different types of cities, ranging from more compact cities such as New York and to more sprawling ones like Houston.
Areas with more extreme temperatures—using heating or cooling systems lowers an electric vehicle’s driving range—and where such larger vehicles as trucks and SUVs are more common will be less likely to increase their use of EVs, said Jeremy Michalek, an engineering professor at Carnegie Mellon and director of the university’s vehicle electrification group. Michalek, who wasn’t involved in the study, said he prefers to focus on the most challenging days for vehicles rather than the average conditions.
“You buy a pickup truck even though most days you’re not loading it full of stuff. You buy it because you have to move some things a few days a year,” he said, noting that most electric vehicles are small or midsize cars. Trancik acknowledged the issue.
The researchers used two data sets, one with second-by-second driving behavior based on GPS data collected from Texas, Georgia, and California and a national data set based on travel surveys. They accounted for different regional driving and weather conditions to conclude that daily energy consumption is distributed similarly across cities for most vehicles.
Trancik hopes the research will show how the potential for EV adoption could exceed even 87 percent. She said the researchers are developing an app based on their model that could tell car shoppers how many days per year an electric vehicle could meet their needs and advise two-car households on which type of car, EV or regular, they should use on high-energy-consumption days.
Regardless of advances in technology and the addition of charging stations, there will always be days on which electric vehicles can’t get the job done. For these, Trancik said, there would need to be better car-sharing services or advancements in other environmentally friendly cars that could fill in the gaps. She also pointed to the need for further quantitative research on EVs.
“Common sense isn’t enough. Common sense leads people to conclude either that the potential is high or low. You have extreme views on both ends,” she said. “It’s important to unpack that question and ask research questions that we can answer quantitatively.”