Either 2/0 gauge copper wire or 4/0 gauge aluminum wire can deliver 200-amp electrical service. Three conductor wire supplies 240 volts of electricity to a main service panel, routing through a main breaker rated for 200 amps.
Two conductors of the three-wire bundle provide two legs of hot current, each at 120 volts. The third conductor of the three-wire bundle ties to the neutral bus bar of the main service panel. For a main panel, the neutral bus bar and grounding bar join with a bonding strap. A 4-gauge bare copper wire grounds the neutral bus bar to a nearby grounding rod.