[8note]

solar heating isnt as passive, and requires that the fluid keeps flowing, and all thr plumbing maintenance that goes with that.

a lot of opinions were made about solar when solar heating was the primary approach, vs today's chinese PVs

[ted_dunning]

This is an important point. In the 1980's, PV panels extracted 5-10% of the incident solar energy which could be converted to heat at roughly 100% efficiency. Solar thermal collectors collected at 80+% efficiency and could store and return the heat at about that level for a net 70% round trip. That's a lot better than PV, especially if the collector is your entire south-facing facade.

Nowadays, panels are sitting at roughly 20% and heat pumps have a coefficient of performance around 4x. If you need a battery round trip, you are right about the 70% point and you now have electricity which is more generally useful than low grade heat.

Those 40 year old decisions, as you say, have had several decades of ossification, though, so it is hard to uproot them.