I'm not an expert. But a Tesla Powerwall type battery is a big thing to install for a renter, is it not? I would argue it's more than installing, say, a washer or window AC; probably more like installing a wall heat pump?

You would certainly need the owner's permission, and investing in the kind of adaptations needed might not be something most renters are interested in when it's not their own place. A battery has to be integrated into the whole electrical feed, and a responsible owner might insist that this is a permanent installation and something you can just take with you when you leave. Or if you do, undoing the install will be similarly costly. And who knows if your next place will allow you to install a battery as well.

I don't think you can realistically install it in an apartment, due to fire regulations, and it needs a lot of space. Personally, I live in a 74 m2 apartment, and there's simply no room anywhere. Wiring is another matter; electricity comes through shared risers I don't control.