One big problem with plug in solar (or batteries) is that they deliver more power than should be available, behind the fuses.

With an 800W panel, an appliance could draw about 3.5A more before tripping the breaker, which can cause problems.

It’s not very likely, but it’s also not the case that governments are just reluctant for no reason. These things being installed poorly is also quite a problem, Germany has had more than a few smashing down from a balcony.

That’s why the power you are allowed to install is limited. And also why they shut down without powet in the socket. The safety issue was a big concern and it took years of deliberation in Germany to get to that point. You can be assured that if something like that is allowed in Germany, it is pretty safe. The safety bodies are watching these issues with hawk’s eyes, and these are professionals which know what they are doing and which move things into a good direction.

Honestly I am surprised why these things are not much more popular in any region where you need climatization in summer - they deliver power when it is most needed, and grids are at risk to fail.

Edit: Addition: If you are concerned, that the panels create more power than the wiring in your home can hold, you can reduce the power in the fuse to the grid. Say, you have a fuse to the grid that allows 32 Ampere, but the wiring holds only 24 Ampere. In addition, you install two balcony panels which have a total of 2000 Watt, or 2 Kilowatt.

Now, what you do: To be on the safe side without the panels, you reduce the fuse to the grid to 24 Ampere, so that the grid can never deliver more than the wiring in your home can sustain. Now, you factor in the panels: 2000 Watt at 230 Volt yield 2000 W / 230 V = 8.7 Ampere. Now, you subtract these from the 24 Ampere that your wiring can hold, and you get to 15.3 Ampere which you can put as the limit to your fuse to the grid. You can round that up to 16 Ampere (which is, by the way, the bog standard rating for household fuses in Germany).

The above number is equivelent to 3690 Watt. That should work, because nowadays the only appliance which draws a lot of power is the electric stove - nobody heats any more using pure electrical heaters since they are just too expensive.

The UK though has the added spice of the uniquely unsafe ringmain wiring standard, in which 24A cable in the wall is protected by a 32A breaker at the distribution panel. It’s only “safe” if the load is evenly balanced around the ring, and the ring isn’t broken (that’s why UK plugs need fuses in them - to make it harder to severely unbalance the ring by pulling 32A out of a single socket, and equally to try and protect the appliance cable if a short or similar tries to.)

I’ve not sat down with a pen and paper to work out how having a generator somewhere on the ring affects things - presumably the authorities have…

But doesn’t the plug based amp mitigate the very problem you’re worried about at the appliance level?

Isn’t that what I wrote?

It’s an imperfect mitigation, though - the typical fuse in the plug is 13A, so you only need two fully loaded sockets and you’re already in trouble. Fortunately these days nobody is plugging in 3-bar electric fires or immersion heaters, and it’s quite hard to find those kinds of loads outside the kitchen, so it’s less of a practical issue, sure. (This is also why UK electrical code recommends that any load greater than 2kW should be given its own radial instead of being plugged into the ringmain. It’s not unusual for the kitchen to be on a dedicated radial (or two) even if the rest of the house is on rings.)

(You could instantly make UK wiring a lot safer by just eliminating the over-rating of the breakers - i.e. if you have a 24A ring, put a 24A breaker on it. In the olden days that would probably have caused nuisance trips (3-bar fires and all,) but these days I doubt anyone would notice.)

Your implication in how you wrote was that the appliances are at risk. However the built in fuses in the plugs should mitigate that

One thing about the old standards is that, as you said previously, it might trip more with less efficient devices, however it was also a case that it wasn’t trip switches, but fuse boxes with physical fuses. So it wasn’t just a hassle, they needed replacement at expense, and a dependency on adequate stock.

Those days are gone, so yes, modern standards should be updated.