Its unrealistic with physics. If entropy was not a thing, you could at best get exactly as much energy back as you used to boil the water with. In reality some of the energy is always wasted and depending on how good your generator is you get some % below 100% out as electricity.

Water is simply not a source of energy. Boiling water requires more energy than you can get by using the pressure of boiled water to drive a generator. Steam is just a way to move that energy from point A to point B.