ICE vehicle engines, except in hybrids and PHEVs, run all the time.
In an EV, you only consume power when you need power. This makes an EV ideal for city driving. When you stop at a traffic signal, your engine stops.
When you brake in an ICE vehicle, your engine keeps running as your forward momentum is converted into heat by the brakes. This means you consume fuel all the time and the kinetic energy is basically thrown away (by turning it into heat instead of future forward motion).
In an EV, when you brake, you are generating electricity. Essentially all EVs have regenerative braking capabilities. Your kinetic energy is stored for future use.
When you climb a hill or mountain pass in an ICE vehicle, once you get to the top, you can coast downhill, but the engine is still running at idle, at a minimum. Your potential energy is translated, partially (not 100% efficient of course), into kinetic energy of forward motion – but chances are that you’ll either use braking (converting kinetic energy into wasted heat) or engine braking (similar).
In an EV, once you have climbed to the top, your vehicle generates electricity on the downhill side, adding miles back into the battery pack. This converts your potential energy back into future forward miles.
As we note below, EVs weigh much more than ICE vehicles. Consequently it takes more energy to lift them up mountain passes, but with the ability to recover some of that energy on the way back down.
