I had thought the same thing about using a power plant's steam output to preheat the inbound water. Turns out, that bringing water up to just below boiling is

I had thought the same thing about using a power plant's steam output to preheat the inbound water. Turns out, that bringing water up to just below boiling is a very small amount of energy, compared to the energy it takes to boil off that same amount of water. As a demonstration, fill a pot with water and put it in the stove. Notice that it will start boiling within about 5 minutes, but it takes maybe a half hour to an hour to boil off the whole pot of water.