
Weighted down with containers filled with water, Not fixed. But this

must be considered as installed. So the same kit depending on how used could be a portable appliance and installed. This

is clearly not installed and likely to be exported to neighbours garden in the next high wind.
A kettle like this

I would call installed, even if plugged in. But on the other hand, it was clear the previous owners had a TV screwed to the wall, due to holes where the screws were, and my TV also held on the wall with a bracket, it would require a tool to remove it, but I would not consider it as installed. It was simply a method to ensure it would not fall over when balanced on small feet.
So my washing machines, tumble driers, dishwashers, cooker, fridge/freezers, freezers, all will likely not be moved until they fail, so are in real terms not different to the immersion heater.
But ask AI, and it says
An installation refers to the act of putting equipment, software, or machinery into position and making it ready to use. It also describes a formal ceremony, a specialized physical facility, or a specific genre of modern art.
so it seems even plugging in a kettle is to install it?
I know 1990s working on Sizewell 'B' there were mobile homes, and caravans, the main difference was a caravan could be legally towed behind a car, where the mobile homes were too wide, and had to be moved on the back of a wagon. Also, mobile homes had a 32 amp plug and socket and the caravan a 16 amp plug and socket (although on a 6 amp MCB) in real terms the mobile home would never move, as no mobile home site would allow one to site a second hand unit, so it was scrapped at end of life, and never moved site to site, so not really mobile. But nevertheless, they were plugged in.
After second world war, we had pre-fabs, designed to last 10 years, OK some still in existent today, but design was for temporary accommodation, so we have

this where he is testing the idea, and is clearly not going to be left in place.
video here and this is the problem, he is clearly not going to complete another G99 as after the test it will be dismantled.
I think on-site guide, showed a whole load of plugs with double adaptors etc, and said there were insufficient sockets, but that could have been a whole load of cordless tools battery chargers plugged in when the house was being built, and may never again get used like that.
The picture shown earlier this
to me is a big problem. Both from the
same site, OK plumbers not electrical, but not being able to close the lid on the socket is a clear problem.
And for someone to write an article on plug in solar showing this, to me is worrying. Plus it means not socket to plug in laptop

clearly a demo, but also something one would not do, I will plug in a 3.8 amp car battery charger, with extension lead, the plug of the extension lead will allow the socket cover to be clicked closed, and the reel and charger are under the bonnet so if it should rain, they will not get wet. And that is something I will only leave for maybe a couple of days.
Why it shows an RCD plug I don't know.