[dendrite9]

A friend in Linkoping showed me his utility closet where they tie into the city hot water system. I was surprised, they seemed too far from the center of town. But I guess the system of insulation and buried pipes makes it reasonable. I believe they had two metered taps into the system, one for heating the home and one for their pool. I assume the metering is based on the amount of water pumped into/out of the house. Is that correct or does it work from temperature differences?

[mwint]

There must be two pipes, one insulated hot side, and one cold side, right? Otherwise the “used” water would cool the hot water going to the next house.

Such a system would presumably be metered by volume, and it’d incentive the right behavior (extracting as much use from each gallon of water as possible).

[dendrite9]

That's what I was thinking. I wasn't sure about things like hot tap water for example. I'd assume the heating water is a closed/mostly closed system like a scaled up version of a radiator system in old houses.

[anttisalmela]

At least here billing is based on amount of energy extracted, so both volume and temperature difference are metered.