National Electric Code 310-315 specifies electrical services wire conductor sizes of #2/0 for copper and #4/0 for aluminum for use in 120/240 volt 3-wire, single-phase dwelling services and feeders. NEC requires a minimum of 100-amp 3-wire service for a single-family dwelling unit.
Two-inch conduits are used to hold the copper and aluminum wires for 200-amp electrical service. In addition, a #4 bare copper conductor is used for the connection between the ground rod/plate and the neutral connection block of the distribution panel for a 200-amp service. A 165- to 200-amp fuse is used on the service entrance wire at the main service panel.