[from occupied ga]

how does a 'heat pump' move the heat around?

It works exactly the same as an air conditioner (an air conditioner is a heat pump)except the cold side is on the outside and the hot side on the inside.

[Svartalfiar]

It works exactly the same as an air conditioner (an air conditioner is a heat pump)except the cold side is on the outside and the hot side on the inside.

I get that part. Where does this heat come from? Just because lake/sea water stays warmer than the air outside doesn't mean there's just heat there to be thrown around. Is it a water pump, moving lakewater around? And somehow staying slightly warm as it circulates the city in the pipes? Is air heated somehow under the lake, and blown around town? So now you need ductwork running to every single building...? And it's somehow insulated enough to not get cold on its journey?