I'm writing this from my off grid shack.

I have 15kwh of lifepo, and even if it weren't hooked to 4kw of solar I could still run my fridge, charge my phone, and run the fan in my fireplace for 4-6 days... longer if I dump the fridge.

It's 6U of deep 19" rack space.

So 2 x that isn't an entire shed-sized battery.

Though I'd happily have a shed-sized battery... I suspect that delivering and covering something that size would cost more than the batteries I already have, though.

For something like a battery backup that last decades that doesn't need maintenance, maybe you could bury it out of the way (like under a deck or lawn?), maybe even under the frost line.

That would you pay for that shed size battery?

It's called diesel fuel.