When it's too worn out for car use (SoH around 60-70%), it's still perfectly enough to run _everything_ in my house for multiple days - except for the electric sauna, and I'm smart enough to turn it on if there are production issues :D
There's a reason why EV's will never be as cheap as the cheapest ICE shitbox. Just the bare metals in the battery are worth thousands when recycled, even more if the battery is still viable.
I did mine with it and old leaf 24kwh battery (~60k km). After all the safety margins I get ~15 kwh out of the battery.
I'm curious what your home insurance provider has to say about your installation.
I'm somewhat sceptical that used batteries will ever be worth much other than as scrap given the cost and complexity in testing, installing, and managing a mixed set of used batteries in larger installations.
With new batteries halving in price every 4 years or so the value of the raw materials in old NMC batteries alone should make it economical to sell for scrap and buy new batteries for stationary use cases after 10 years or so!