In Europe, much fewer people live in houses, and thanks to the dense, walkable cities they enjoy, they have much fewer roof and yard space to put the panels. Also, unlike US, most of Europe doesn’t have huge swaths of hot and sunny plains that are currently not used for anything valuable. Look at the satellite view of Germany, France or Poland: it’s all farms, with occasional forests.

I do live in Europe and lived in various European countries, that being said the apartment buildings could also have a similar solution (their own solar panel/wind turbine/geothermal) OR simply do that in a more localized way (each city has their own solar/wind farms). Combine this with more regulations regarding energy saving/consumption (promote more efficient electric devices).

In the end I see it as having multiple independent energy-generating clusters (each building, or each city, or each country) and sharing excess energy outside the cluster only when needed.

> the apartment buildings could also have a similar solution (their own solar panel/wind turbine/geothermal)

They can’t, though. Apartment buildings are too efficient at packing people together to have enough per capita roof square metrage for panels. Practical wind turbines are huge. A typical wind turbine blade is longer than the height of a 10 story building. Geothermal is also rather impractical as a source of energy, due to low thermal conductivity of the rock.

> In the end I see it as having multiple independent energy-generating clusters (each building, or each city, or each country) and sharing excess energy outside the cluster only when needed.

You are describing here exactly the current status quo. That how energy works right now.

You need a lot of PV per person if you want to satisfy all their primary energy needs. On the order of 150sqm. Apartment buildings don't have enough roof space to be self-sufficient.

The capex to do that was unreachable for the vast majority of the population, even when money was ‘cheap’.