Most states involve 100 amps minimum, but with all the new electronic devices, air con and electric heat, i might suggest 200 amps especially in new homes. This may also provide you some space for future renovation. This is often not a job for an unlicensed person to aim. In most cases it involves replacing everything from the service loop (this is that the wire that extends from the highest of your meter to the utility tie in ) up to and including the most panel.