If you’re considering getting an electric car, here’s an important thing to bear in mind: It may work better in some parts of the country than others. There are big regional differences in EV performance, with very hot and very cold areas generally doing worse than temperate ones.
Researchers from Carnegie Mellon University studied data from hundreds of Nissan Leaf drivers (7,000 trips in all) tracking the effect of outside air temperatures. In Phoenix, where temperatures regularly exceed 100° F, driving ranges dropped by as much as 29% on hot days. In Rochester, Minnesota, they fell by as much 36% on the coldest days. That means a Leaf that’s advertised to go about 70 miles on a single charge might only go about 45 miles.
“There is a risk of reduced range in extreme temperature, so in regions with hottest or coldest peak days, consumers considering an EV purchase should be aware that a 75-mile rating could mean closer to a 45 mile range in practice on those days,” says Jeremy Michalek, the CMU professor who co-authored the study.
Electric vehicles consume more energy on cold and hot days for two reasons. One, batteries are less efficient when they get cold. And, two, because heating and cooling requires more power than normal. The advantage of a gasoline or hybrid electric car is that the engine produces excess heat that can be used for heating. On average, the energy consumption of Leafs in the Upper Midwest or in the Southwest increased by 15% compared to those in the Pacific Coast and the Southeast.
Not every EV in the Midwest is going to poop out at 45 miles. The point of the study is to show possible range due to weather extremes. Temperate San Francisco, by contrast, is more consistent: Leaf drivers there saw ranges of 70 miles or more 99% of the time.
The study also looked at differences in EV-related carbon emissions across the country, and again the differences are stark. CO2 emissions per mile are three times higher in the upper Midwest than on the Pacific Coast, largely because of the latter uses dirtier forms of electricity generation, like coal.
Over time, as coal plants are phased out, the variations may narrow. But for now they could affect what car you want to buy. Michalek says in some places hybrid-electric vehicles, like the Prius, may produce less overall greenhouse gases than pure electrics like the Nissan Leaf. It just depends on where you live.