Reuse of vehicle sized packs seems to be pretty common, though. I'd guess that a DIY home backup could be built pretty easily from used vehicle batteries.
Give me an array and battery system that can pull off the grid and/or array and power most of my home without me having to think a whole lot or pay a vendor thousands to install while making the total cost under $1000 and I’ll do it.
Until then, it just isn’t financially viable when my electricity costs are well under $70/month average across the year.
Recouping the costs for install of solar systems are estimated at 30-40 years as of 4 years ago when I researched it. I’m sorry, but that’s just not worth it for me and most others.
I don't want to detract from your point. I just wanted to appreciate the hyperbole.
Cost is always an issue. These rarely make sense from a pure $$ sense, as everything in electrical is expensive. You could burn up that $1000 budget just to get a subpanel installed.
Usually the value proposition is some combination of savings, combined with the ability to backup critical loads. A generator could do that too, but a proper generator setup isn't cheap either, and it wouldn't save $$ at all. Battery solutions sometimes beat that.
But net metering is becoming less common, and if you can't sell to the grid at retail, then it'd make sense to store it locally. In some cases, it can also make sense to use batteries even without solar. A good sized battery can keep your refrigerator running for days, which is useful for areas prone to weather related outages. It can also easily fully power the electronics on a gas oven for a long time. And honestly, a big battery these days isn't even that expensive.
And if that isn't enough, some batteries can be topped up with the power from a large battery EV. DCFC tends to come back before a lot of residential power, so this can be really useful.