What happens to the electric energy if circuit is not complete but energy is in wires?
Think of something suspened above the ground. Until it is released it has potential energy, once released it becomes kinetic energy, and when it hits the ground it becomes heat. Similarly the energy in a battery is potential energy until the circuit is completed, and then, most probably it will become heat; unless part of it becomes light, or sound, or something else. If a generator is churning away, and no power is being drawn, it will have to work less hard, and it will consume less energy, because there is no back EMF. What energy it does consume is being used to overcome the friction in its bearings (and air resistance).
