Two electric vehicles can carry a battery pack of the exact same rated capacity, built on the exact same platform, and still arrive at wildly different EPA range numbers, because the battery is only one variable in the equation. Hyundai’s own Ioniq 5 and Ioniq 6 make that case better than almost any pair of EVs on sale. Both offer a Long Range configuration built around a 77.4 kWh battery pack on Hyundai’s shared E-GMP platform, yet the EPA rates the Ioniq 6 Long Range RWD at 361 miles on 18-inch wheels while the Ioniq 5 Long Range RWD manages 303 miles, a 58-mile gap between two cars carrying an identical battery. The difference comes down to one engineering decision most shoppers never think to ask about: how much air the body has to push out of the way.
Same Battery, Same Motors, Radically Different Shape
The Ioniq 5 and Ioniq 6 are not just related, they are mechanical siblings. Both ride on Hyundai’s E-GMP architecture, both offer the same 77.4 kWh Long Range battery, and both use closely related motor hardware. What separates them is the body sitting on top of that shared foundation. The Ioniq 5 is a boxy, upright crossover styled to echo the original 1970s Hyundai Pony, while the Ioniq 6 is a low, teardrop-shaped sedan Hyundai designed almost entirely around minimizing drag. According to Hyundai Motor Group’s own engineering account, the Ioniq 5 achieves a drag coefficient of 0.288, which the automaker itself describes as competitive with, but not exceptional among, other electric SUVs.
A Coefficient of 0.21 Changes Everything Downstream
The Ioniq 6, by contrast, was engineered around active air flaps, a rear spoiler, and wheel air curtains specifically to chase a lower number, and its published specifications, summarized alongside Hyundai’s official technical documentation, credit it with a drag coefficient as low as 0.21, one of the lowest of any mass-production vehicle sold anywhere. That difference of roughly 0.078 in drag coefficient sounds small on paper. At highway speed, where aerodynamic drag is the dominant force an electric motor has to overcome, it is large enough by itself to explain most of a 58-mile range gap between two cars whose batteries are otherwise identical.
The Same Pattern Shows Up Between Direct Rivals, Too
This is not unique to one automaker comparing its own two models. Hyundai’s Ioniq 5 and Kia’s EV6 share the same E-GMP platform, the same 77.4 kWh Long Range battery option, and largely the same drivetrain hardware, yet EPA figures compiled by InsideEVs show the EV6 Long Range RWD rated at 310 miles against the Ioniq 5’s 303, and the gap widens in all-wheel-drive form, where the EV6 reaches 274 miles compared with the Ioniq 5’s 256. InsideEVs attributes the difference mostly to aerodynamics and vehicle weight rather than anything mechanical inside the battery pack itself, and the numbers back that up: the EV6’s more sharply raked fastback profile carries a drag coefficient of roughly 0.28, measurably lower than the Ioniq 5’s more upright shape, according to Kia’s own published specifications.
Weight, Wheel Size and Motor Tuning Stack on Top
Aerodynamics is the largest single factor, but it is not the only one. Wheel diameter alone moves the needle within a single model line. InsideEVs’ comparison notes that stepping up to larger 20-inch wheels drops the Ioniq 5 Long Range AWD’s range from 256 to 244 miles, purely from added rotating mass and reduced tire efficiency, with no change to the battery at all. Curb weight differences of even a couple hundred pounds between otherwise similar EVs, along with how aggressively an automaker tunes regenerative braking and motor efficiency at partial throttle, layer additional range gaps on top of whatever aerodynamics already accounts for.
What This Means for Anyone Comparing Range Numbers
None of this shows up on a spec sheet the way battery capacity does. Two EVs can list an identical kilowatt-hour figure in bold print while their real-world range differs by double-digit percentages, and the reason is baked into decisions Hyundai and Kia’s engineers made years before either car reached a showroom floor, namely how the body is shaped, how much it weighs, and how efficiently the motor converts stored energy into forward motion at highway speed. A buyer cross-shopping by battery size alone is comparing the wrong number. The EPA-rated range printed on the window sticker, which already accounts for all of these variables together, is the only figure that actually tells the full story.