Service entrance wire size is AWG # 3 copper.
A 100 amp residential service requires a size #8 copper wire, it should be insulated in green.
Service wire for 100 amps requires AWG #3 copper.
The minimum size grounding conductor for a 100 amp service is a #8 bare copper wire.
#2 wire copper
Service entrance wire must be AWG # 4 Copper wire.
A#3 bare copper conductor is used for a ground wire for 100 amp service.
A 100 amp service requires that you use AWG 4 copper wire or AWG 2 aluminum wire.
AWG 4 copper.
A #3 copper wire with an insulation rating of 75 or 90 degrees C is rated at 100 and 110 amps consecutively.
A #3 copper wire with an insulation factor of 75 and 90 degrees C is rated at 100 and 105 amps respectively.