Two heat exchangers, one big for the hot water, one smaller for the heating. Heat comes in the form of water at 10bar/75°C. Everything is packed in a box having the a size of 1m (H) x 50cm (L) x 30cm (D). Isolated delivery pipes are all under the city block.
We have that at home, this is great. No noise, no maintenance, no emissions. The only downside is that you are "locked in" with a single heat provider.
My best friend family built a house 15 years ago, when the tech was new-ish, and the pipes are under the cement and inaccessible without huge costs. Then their house settled a little over the years and it lead to maintenance issues.
I suppose new installation don't have the issue, but for stuff I'll use for a long time (basically house, computer and car), if I don't know how to repare it, I prefer old tech.
Wouldn't you need pipes anyway for regular plumbing? That would have lead to issues anyway, right? Also I doubt somewhat the tech was new 15 years ago, it's quite common in germany to use district heating, especially if there's a source nearby you can use or it's a bigger city. So I am pretty sure district heating is very old-tech, just geothermal source is new. German wikipedia says:
> About 9 % of the total heat demand in Germany is covered by heat grids today and 14 % of the demand for residential buildings.
It's less efficient than lower temperatures, but this district is built without gas lines to the houses (as is normal in The Netherlands till recently), and it's more efficient than everyone having an electric boiler in their house.
The pipes are well insulated and apparently the energy loss quite manageable.
The efficiency mostly comes from _moving_ heat that already exists, instead of creating new heat.
Depending on the specifics, that's often about 5x more efficient.
Counterintuitively - the "heat" source doesn't have to actually be hot. In theory as long as it's above absolute zero it can be used as a heat source to heat up the inside of your home. It's the same for cooling - even if it's hot indoors and really hot outdoors, you can still use a heat pump to make it even colder inside the hosue.
We have that at home, this is great. No noise, no maintenance, no emissions. The only downside is that you are "locked in" with a single heat provider.