Comment by cyberax

Modern elevators have regen braking, so they can recover most of the energy spent on going down. Older elevators used braking resistors for that.

(BTW, going _down_ while empty is typically more energy-consuming for the elevators because they are counterweighted)

Edit: that's also why you shouldn't use elevators in a fire. If the brakes in the elevator machine room fail, the cab won't crash down. It will go _up_, possibly dragging you into the fire. Many firefighters died because of that.