You have two options, one is a complete service change. The
average house service these days is 200 amps 42 circuits. The
second option is to install a sub panel off the existing service.
Depending on how many circuits you need will govern the size the
sub panel. Here is where it gets tricky. Two side by side single
pole breakers or one two pole breaker will have to be removed from
the original service panel and replaced with a new two pole
breaker. The size of this breaker will be governed by the total
load of the new sub panel. The wire from the new sub panel to the
two pole breaker is also governed by the load of the sub panel. As
an electrician I would recommend that you not do it yourself but
get a qualified electrician to do it for you. He would (should)
take a permit out for the job and get it inspected.
