A bigger battery pack may be the most straightforward way to increase an EV's range, but that approach is limited by cost and packaging considerations. One of the most important single factors for highway efficiency of EVs is aerodynamic drag, and as a recent Hagerty video featured below helps underscore, bigger cars aren't necessarily harder to push through the air.
Reducing a car's coefficient of drag (Cd) means less aerodynamic drag at speed, which in turn means the car requires significantly less energy to push itself through the onrush of air at higher speeds. With less energy needed to propel a car a given distance, it can go farther on the same battery pack than a same-size car of the with a higher Cd.
Note that the effective frontal area can be different from the actual frontal area. A car with a Cd of 1.0 has an effective frontal area that matches its actual frontal area, but most production vehicles today have coefficients well under 0.50, indicating the importance of the wind tunnel in the modern auto industry—as it should be.
2020 Tesla Model X
The coefficient of drag can make the effective aerodynamic resistance of a large car no worse—or perhaps better than—a very small one. As noted in the video, a Tesla Model X has a lower Cd than a tiny Lotus Elise two-seat sports car. Once frontal area is considered in the calculation, more energy is required to push the Lotus through the air than the seven-seat Tesla SUV.
It's not, of course, considering rolling resistance, which rises with weight, and the physics of accelerating, climbing hills, and merely maintaining speed. But aerodynamic drag can factor in as roughly half of the overall energy demands of highway driving.
Lucid Air tri-motor prototype testing at Laguna Seca
Tesla and other EV makers are well aware of this, and low drag coefficients are a fixture of EV press materials. The Mercedes-Benz EQS has a 0.20 Cd, according to its maker. Lucid Motors claims 0.21 for the Air—and it might be a bit lower in some versions, the company has hinted.
While these sedans have smooth, lozenge-like shapes, big and angular isn't always bad. Elon Musk has claimed that with some tweaking the Cybertruck might be able to achieve a 0.30 Cd.
These vehicles are likely no match for the Volkswagen XL1, though, with its 0.189 Cd and compact-car frontal area. The efficiency-focused XL1 wasn't designed for the mass market, however. The Lightyear One is also billed as having a drag coefficient below 0.20, but with a somewhat more practical four-door body style.