A#3 bare copper conductor is used for a ground wire for 100 amp service.
The minimum size grounding conductor for a 100 amp service is a #8 bare copper wire.
#8 is the size of wire to use for grounding a 100 Amp panel. Green is color used for grounding #8 is code.
Service entrance wire size is AWG # 3 copper.
2 AWG Aluminum for 100 Amp Service.
Service wire for 100 amps requires AWG #3 copper.
To calculate the wire size, a system voltage is needed.
Service entrance wire must be AWG # 4 Copper wire.
#2 wire copper