Most of that energy gets transfered to the air that's being moved by the blades, and who knows what that air does eventually. And we're not even talking about the plant growing light that might be sitting in my room near my house plants literally creating new life from electricity.
We do know what that air does eventually. Given no further inputs of energy, it swirls around generating friction, raising its temperature (heat!) as the currents slow down to nearly nothing.
