and some random line worker may think there's no electricity flowing when there is.

(But yes, backfeeding the grid during an outage is dangerous and highly against code.)

If you have lines in an unknown state, step 1 is to put them in a known state. For power line work, this involves grounding all the phases and neutral together at both ends of the section you intend to work on. Good luck ringing a dead short with your home inverter/generator/etc.

Is that conceptualisation correct?

What happens is you have say a conductive (iron rich) top layer. Is there still the potential to dangerously energise the ground? I assume so because that's basically what water and electricity does?

Grounding provides an alternate path for the flow of electricity, so if a wire comes loose and ends up touching a copper pipe or something the current gets routed into the ground rather than into pipes or flammable wood or something.

Dispersal over an area isn't directly the goal, but it helps. By dispersing the current into an extremely large object, you don't really have to worry about the object building up a charge to the point where you can't flow current into it anymore.

Yes, you can dangerously energize the ground. You can dangerously energize almost anything with enough voltage. E.g. a Tesla coil has enough voltage to conduct through air. Don't try to test it (obviously), but I don't think a standard 110V house grounding has enough voltage to dangerously energize ground over any significant distance.

In Europe you should check if grid-independence is even legal. In some places it is not.

I suspect the dividing line is voltage? >50v systems in cars are treated differently, so maybe the same for houses, you probably don't need that much for lighting anyway.

Most people unfortunately can't take advantage of this, but most battery packs are also suitable for off-grid use.

Efficiency.

You can store excess energy from local microgeneration, particularly solar, that can be used later. With our current pricing model in the UK, that is several times cheaper than selling the excess power to the grid for a token return and then paying full price to have the same amount back from your mains supply later.

Some systems can even be configured to charge their battery from the mains at quiet times (when, again in a typical UK pricing model, the cost-per-unit can be much lower) if there isn’t enough local generation to fully charge it, for example in the middle of winter.

https://www.utilitydive.com/news/utility-scale-battery-stora...

https://www.ny-engineers.com/blog/two-ways-to-use-grid-tied-...

Things like https://www.hawaiianelectric.com/products-and-services/custo... note the https://www.hawaiianelectric.com/products-and-services/custo... - the CGS Plus and Smart Export involve use of a battery that isn't necessarily home power sufficient.