Technology

The infinitely easier solution is to let the car charger know how much power is available to draw.

1. Sometimes breakers don’t trip, so there’s a small risk of fire
2. Restarting the whole house may have large initial loads as everything starts at once: more chance of it happening again or potentially damaging some appliances
3. Risk of heat damage to wiring with repeated trips, risk of broken connections from more frequent expansion from heat/cool cycles
4. Inconvenience, especially in the old days when you’d have to go through to set clocks. If while asleep you might not be awoken in time. If you weren’t home, maybe food gone bad
5. Occasional home health appliances are critical to keep going

Realistically it comes down to how conservative you are with over-provisioning. You might also expect it to handle the load for 50 years of growing usage. In the US we have the expectation of rarely to never tripping the main and when that happens it’s more likely an electrician call

I don’t think overprovisioning is a thing that is realistically is a problem in the U.S. or in Germany. I know that modern homes tend to have 300amp mains. Older homes 100amps. You would have to have a house that was wired in 1920 in order to have a 20amp mains available. In that case you have bigger issues safety wise.