You aren't missing anything, that's pretty ludicrous. My (midwest USA) house has 100A service, and I weld for fun and run a rack with servers. The welder can

You aren't missing anything, that's pretty ludicrous. My (midwest USA) house has 100A service, and I weld for fun and run a rack with servers. The welder can make the lights dim which makes me want 200A, but 400A is just insane.