Ah, right I was picturing an oversized car battery that you can lug around. Extension cord then? Not sure but this seems surmountable without having to rewire the house and get a permit or licensed unit for feeding the grid

The size the article is talking about are usually around 100 pounds or ~50kg at least. My solution is the much smaller Anker Solix C1000 and it's outboard battery extension. It can output up to 1800W sustained with a 2.4 KW peak and the two units together have about 2100 Wh of capacity. They're small enough to move around by hand when disconnected but can't do the kind of peak shifting the OP article was talking about so they're purely backup or car camping power. I used them to power my WFH setup while my electrical service was being upgraded a while ago though and it worked well enough.

Right, and some of us have a fine tradition of using extension cords as a way of powering some things during an outage with, eg, a portable generator buzzing away outside.

It's clunky and haphazard, but it can work well-enough for rare use.

But one of the big sells in the article for this device is that it can be used to buy power when it is cheap, and sell power when it is expensive (at least in markets that support that kind of operation). This can be good for the owner (who can make some money doing it), and also good for the grid (the price fluctuates when supply and demand aren't well-balanced, and this function helps to balance things).

That kind of functionality, on its own, can tend to require some real wiring changes and permitting.

(Or not. Electricity rules vary wildly around the world. They aren't even necessarily consistent within one nationality.)