Long-term energy storage with hydrogen, with 1-5x 300 kWh. Which allows for full electric independence (not including heating though). Price: 85,000-125,000 €, minus government subsidies.
Your energy consumption for heating might be ~ 3000 kWh/month during the winter months (Nov-Mar) for a moderately insulated house.
Assuming your PV produces only 10 % of the demand during these 5 months (so you have to rely on stored energy for the remaining 90 %) and your heat pump delivers a Coefficient of Performance of 3.5 then you'd need to store ~ 3900 kWh.
As to my back of envelope calculation, one standard 50 l bottle of hydrogen contains ~ 30 kWh worth of energy when filled at 200 bar.
So you'd need ~ 130 such standard bottles to store enough hydrogen.
That's quite a lot. But of course with a well insulated home, you'd maybe only need a third, so that'd be 3-4 bundles (with 12 bottles each).
Hydrogen embrittlement seems to be an unavoidable problem so not sure how that plays out.
For now and maybe always, it's probably more cost-effective to size the solar-electric system for winter months (if adequate roof / ground space).
Still, it definitely cannot generate enough to bring you through the german winter. Some example numbers I have read: A 10kWp solar system that generates up to 1,400 kWh in a summer month will only provide about 200 kWh in December.
And if you position it N-S you'll get slightly less power than a standard setup, but it'll be less concentrated in the summer, and also spread through the day more.
https://www.sciencedirect.com/science/article/pii/S266695522...
This is a pioneering product for early adopters - expect prices to go down significantly with economics of scale. And further research in this area is far from exausted.
My point is: Deploy nuclear power now, continue RND on large scale hydrogen storage that maybe will pan out in 20 years.
As always, There is No Silver Bullet™.
Nuclear is not the perfect solution. It cannot be powered on and off on short notice, which would be useful for complementation of solar and wind that have high power output, but also sudden slumps. Ironically, the ideal companion for renewables would be gas...
Lithium batteries could compensate short outages, but don't have enough (feasable) capacity for long seasonal shortages.
Enter Power to Gas. Hydrogen can be a good tool in that area.
A commerically available hydrogen storage system (that is in high demand even despite its price point) will definitely accelerate innovation very effectively. I think this tool will be available quite soon for mere mortals.
The tech for building reliable, safe, affordable, large-scale hydrogen "batteries" isn't here yet.
So the solution is simple. Nuclear has its place. Power2Gas too. Build and invest in both. And in the meantime, use what we have without ideolgical eye patches.
I can sharpen my argument even further:
Existing nuclear reactors - keep them going. They are here today.
Solar - leverage its decentralized, bottom up expansion by the people that can use their own roofs, reduce beaurocratic hurdles. Its expansion does not have to wait 8 years. The products are here today.
Power 2 Gas - celebrate existing products on the market. They are here today.
All these things are here today and part of a solution which contains many parts. I welcome each and every betterment, because we will need it.
You on the other hand are dismissing key tools and instead focus on one thing that is not here today and will maybe be ready in 8+ years.
You may find this interesting:
https://www.reddit.com/r/dataisbeautiful/comments/wvjfiy/how...