The thermodynamic gap between electric and combustion
An internal combustion engine converts roughly 20-30% of fuel energy into usable motion at the wheels, with the remaining 70-80% lost as heat through the radiator and exhaust. By contrast, an electric motor converts 85-90% of battery energy into motion, discarding only 10-15% as heat. This is not a matter of engineering optimization but of fundamental thermodynamics: chemical engines are inherently inefficient heat engines operating at modest temperatures, while electric motors convert electricity to motion directly.
This efficiency gap translates to real-world costs. An EV consuming 4 miles per kWh at $0.14/kWh costs roughly 3.5 cents per mile for energy, while a gasoline car achieving 25 mpg at $3.50/gallon costs 14 cents per mile for fuel. The electricity cost is one-quarter the fuel cost for equivalent mileage, a difference that compounds over the car's lifetime.
Regenerative braking and the efficiency advantage
EVs recover energy during braking through regenerative braking, converting the car's kinetic energy back into battery charge rather than dissipating it as heat in brake pads. In urban stop-and-go driving with frequent braking, this recovery can amount to 10-20% of the distance traveled for free. Gasoline cars cannot recover this energy, making them even more inefficient in city cycles.
The efficiency advantage of electric propulsion means EVs achieve their best performance in real-world mixed driving, not on highways where the smaller payload and lower power demands of modern gasoline engines narrow the gap slightly. Still, even at 70 mph on the highway, an EV typically achieves 2-3x the energy efficiency of a comparable ICE vehicle, which is why grid decarbonization heavily favors electrification of transport despite the manufacturing emissions of batteries.