Combined cycle power plants can be 64% efficient [1] at turning heat into electricity. And if that power goes on to run a heat pump, 1 watt of electric power can deliver 3-4 watts of heating.
And modern gas combi boilers can be 92-98% efficient [2].
The days of people throwing away 80% of the energy they pay for are long gone.
Could you give some examples for nuclear power plants that are using a combined cycle turbine? I was under the impression that the operating temperatures of BWRs or PWRs are nowhere near high enough for that.