A 1 MWh battery isn't actually that big. There's electric trucks on the market right now with 600 kWh batteries sitting on the frame between the front and rear axle. That would easily fit into a basement room.
I wouldn't want a battery in my basement. if there is a fire in the battery your house will turn into a smoking hole, in the literal sense. Maybe if it was an iron-air battery or something safe, but not the current generation chemistry batteries.
Seems like the peak was around 2017 but they never performed particularly well?[1]
The problem is if the promise from the name was true, they'd be everywhere - they're not, so invariably much like vanadiun-redox or iron-flow batteries it turns out all the other details make them more expensive and less performant.
" if the promise from the name was true, they'd be everywhere"
Not necessarily.
Lithium is still quite cheap, safety is not the number one demand - and it is mainly about optimizing production to achieve competive pricing.
So yes, mabye there are some blocking details I am not aware of, but otherwise I expect their time will come.
Even if it was a safer chemistry, I would still put it outside of my house, likely in a dedicated structure. Its a shit ton of energy potential regardless, and it can make maintenance and modification down the line way easier.
Most grid-scale batteries that large will have bigger inverters (usually it'll be inverters that can dump that energy in 2-6 hours so 500-150 KW for 1 MWh of battery) and require cooling systems and such, but if you're putting that in your home then cooling will be negligible and the inverter will remain small. The batteries themselves are fairly compact, it's the support systems that get large.
We can roughly estimate lithium ion batteries as 500 watt-hours per liter. Which makes a million watt-hours 2000 liters, which is two cubic meters. Add in extra overhead and it's still not all that much.