Yeah, in combined cycle plants you burn the natural gas first in a gas turbine first, use the waste heat from that to boil water and run steam turbine. Then condense the steam using your district heating circuit.
You can say this is 100% efficient as you make some electricity and the rest does house heating.
The thing is that your home's heatpump has an efficiency of 300%-500%. So even if your power plant and power delivery only has say 50% gas-to-electricity-at-home, you are still looking at 150%-250% gas-to-heat-your-house efficiency.
You can say this is 100% efficient as you make some electricity and the rest does house heating.