[PunchyHamster]

hot water also have pretty high losses, because you need to keep it cycling constantly to keep the heat up (you don't want a case where opening a tap in the morning means letting up the hot water from the 30m length of pipe from the street to your house).

So paradoxically, if your heat is not "free" (cogenerated with electricity) it might be far more efficient to have a boiler in each house (and definitely a heat pump), than to push the heat that far away.

[trollbridge]

In a modern system, you'd pull the heat from the hot water using a heat exchanger or a heat pump. (I'm also assuming a closed-cycle.)