Going to be much more challenging in Europe and cooler climates with less sunshine.

Sunny places like Australia are having the problem of too much solar on the grid now and looking at community batteries and EV charging as ways to offset that and stabilise things.

I'm at +45° north and it should work fine here (I'm basing all my assumptions on where I live). It most definitely wouldn't work in Sweden and Norway, but France and maybe even northern Germany should be fine?

I just did some quick calculations (which might be wrong, but maybe not by orders of magnitude) based on reported numbers on the internet. It seems that powering a medium sized air source heat pump purely on solar in a UK winter would require a £34K investment in solar panels, covering nearly 300 square metres. Not exactly viable per property in city-density housing.

City dense will never work since skyscrapers have ridiculously low roof amounts compared to the populace.

Also, as far as heating goes, passive houses should need almost nothing for the winter (still need to heat water for showering, etc. though).

E: Can you share your numbers? A 10kWp plant that I had in mind is ~50m^2 - 30x330kWp panels at about 1.6m^2 each, so did you mean you actually need a 60kWp plant?

Sorry, I didn't save the numbers.. But yeah, sounds right - based on reports that we can only expect 1/5th of the output per panel in winter.

"Passive houses" are not going to happen in the UK for the vast majority of the population in my lifetime!

45N is basically northern Mediterranean; most of Europe does not have similar climate. It does not work fine even at 48N during november-february.

Makes one to think how much of the solar capacity will end up simply unused during peaks. That is it is there, but the relays have disconnected it. As we simply will not have enough places to sink it all and for grid stability you can't produce more than you use...

Unfortunately one of the biggest technical problems with renewables is that we still lack an efficient way to deal with energy storage. It's still relatively expensive, inefficient, and creating waste. Maybe in 20-30 years you will be able to live in the winter using the energy produced during the summer and stored in batteries that are cheap and 100% recyclable, but it's not a reality yet.

20-30 years is optimistic IMHO. We're still a huge technological breakthrough in batteries away for large-scale, high-capacity energy storage to be viable.

It might happen, but the technology still isn't there, yet we're going all in on renewables, especially in countries like Germany and Italy where nuclear is politically toxic.

“PV Diverters” supposedly remedy that problem. They use current transformers to detect when the home’s solar supply is outstripping its demand, and then switch on power consuming devices like electric water heating / air conditioning so the power isn’t wasted.

10kWp is not enough during winter (november-february) in most of Europe. It would be enough only if you heat by using something else (like gas), not heat pump.