Overcoming air resistance accounts for 45% of the total energy demand at the highway driving speed of 55 mph (24.6 m/s). This is calculated based on the frontal area and the aerodynamic drag coefficient, both of which are a direct consequence of the cabin design. Therefore, the cabin design strongly influences the observed fuel economy for trucks, for both battery electric and diesel alike. However, the economic implications are significantly disparate. Based on the targets of the SuperTruck program by the DOE 104 and the reported drag coefficient for the Tesla Semi, we recalculate the TCO per mile using a drag coefficient value of 0.35 (See Supplementary Information for details). It should be noted that the SuperTruck values are future targets (aspirations) and the Tesla Semi features a day-cab compared to a more common sleeper cab used in long-haul trucking. Therefore, this is an optimistic outlook on the truck design. Diesel trucks only benefit from fuel savings, reducing TCO per mile by 0.05 USD/mile (0.03 USD/km). On the other hand, BETs benefit in multiple ways: lower capital cost due to a smaller battery, lower payload penalty factor, and lower electricity consumption. This leads to a saving of 0.42 USD/mile (0.26 USD/km) for the present-day scenario compared to our base design with a drag coefficient of 0.6. While this is a very substantial saving, it is not enough to make BET competitive with diesel today even if delivered electricity at the charger was free. Low-drag BETs become more competitive in the mid-term and long-term scenarios, but would still need very low total delivered electricity prices of 0.04 USD/kWh and 0.07 USD/kWh, respectively, to break even with low-drag diesels. While the price of delivered electricity at most high-power DC chargers in the USA is not expected to get this low, these prices might be achievable in certain locations.