[iguy]

Interesting figures. BTW, the terminology is a mess, but I think what you're describing would most clearly be called "district heating", as "central" often just means that your house has one burner in the basement (as opposed to a fireplace in each room, originally). I hadn't stopped to think what the museum would have.

And, somewhere in here there's a parable about capitalism. The engineers are correct that the district heating plant has economies of scale... but it's only as clean as your town's politics, and even a squeaky-clean mayor has to make a terrifying giant decision about whether to upgrade it, once every 30 years. Instead of every owner gossiping with his neighbors about what works & what breaks, and whether double glazing was worth it.