A couple of years later someone showed me a PowerBook and that was that.
They need to e.g. provide the proper frequency on their own and entirely/physically decouple from the grid etc.
They are available but just rooftop solar and a battery is not enough.
It’s not a mainstream feature and there’s a high setup cost but the tech is readily available and the price/kWh of home batteries is going down steadily.
The second fuse at the plug allows using a narrower gauge of wire in the device’s cord. Let’s say you have a lamp with a 3A fuse, the cord only needs to be able to handle 3A, so then it can be lighter and cheaper. If it had to handle the same amperage as the circuit it’s plugged into then it would be seriously impractical and expensive.
Of course there are modern ways of solving this but fuses are dirt cheap and already implemented.
This means you don't have breakers for each branch circuit (there are no branch circuits), just the single mains breaker for the house. This single breaker is too large to trip from a short from occuring in the smaller wires inside an appliance.
So each plug (or hardwired device) needs it's own dedicated smaller fuse instead.
Lighting rings are also separate, usually on 6A breakers. We cheap out on cable by not running neutrals to the switches, which causes nerds headaches when they want to install generic smart light switches.
My house is reasonably large (worked hard, all my own money) and has a 20-way distribution board with separate socket and light rings for groups of rooms. It’s handy for isolation purposes.
More recent builds’ rings will be protected by a combination of MCBs and RCDs, or individual RCBOs (now the cost has come down) which combine the two functions and is ultimately the safest option for most situations.
Individually fusing plugs (and in the case of high-draw appliances like washing machines and dryers, protecting with a fused socket) is still a very good idea. And don’t get me started on earthing practices in other countries…
I have a commit of ~15bn queries/month with my DNS provider ATM, and if just one busy record has its TTL set erroneously low, it can cost an extra few thousand $ a month in overages. It’s not a great conversation to have with the CFO when that happens. Caching matters.
Everyone else - particularly cold-call sales droids - can do one.
Powerlines suck, but when you have no other option, they suck a little less than no connectivity at all.
If your VDSL line runs anywhere near your mains wiring, they can cause crazy interference and erroring as the frequencies overlap. Some kit has a notch-out mode to avoid this (Devolo I think).