That is what the electric companies will tell you and what they really want you to believe. As far as the point of heating, it is 100% becuase there is no vent to release any heat.
However, in my area the steam that drives the turbine is heated with coal and even the best turbines loose 40%. The turbine exhaust has to be circulated through the cooling towers and anyone who doesn't believe they are loosing energy can witness the steam cloud coming from the top of the towers. You know, those things they show on TV and say they are 'belching out polution', well it is only steam.
My whole point is, electricity is 60% efficient with the best new turbines. And hydroelectric power blows my case out of the water.