You would have to spread that load across multiple circuits in your house to avoid tripping breakers/blowing fuses. You might not have enough capacity to absor

You would have to spread that load across multiple circuits in your house to avoid tripping breakers/blowing fuses. You might not have enough capacity to absorb all 400A if the original installer oversized the main breaker to allow for additional capacity later. The bad thing is you would get a huge power bill at the end of the month.