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When installing or upgrading to a 100 amp electrical service, one of the most important decisions is selecting the correct wire size. The right wire size helps ensure safe and efficient power delivery to your home or building. This article provides a detailed overview of recommended wire sizes for various 100 amp electrical service scenarios.

Wire Sizes for 100 Amp Electrical Service

Wire Size for 100 Amp Main Service

For a main 100 amp service panel, the recommended minimum wire size is 100a copper wire size with a 3/0 AWG conductor. This applies to both overhead and underground 100 amp installations. 3/0 AWG copper wire provides a sufficient ampacity for a 100 amp panel while meeting code requirements for safety and performance. The 100 amp awg and thickness of 3/0 AWG allows for adequate current flow with minimal voltage drop.

Wire Size for 100 Amp Sub Panel

When installing a 100 amp sub panel fed from the main panel, the recommended wire size is also 3/0 AWG copper. This 100 amp panel wire size maintains proper current flow for both the main and sub panels. While #1 AWG wire is sometimes used for 100 amp sub panels, the thicker 3/0 AWG is ideal for handling the full 100 amp load and allows room for expansion. Using the proper 3/0 AWG wire size for the 100a sub panel helps avoid voltage drops over longer wiring runs.

Aluminum Wire Size for 100 Amp Service

For a 100 amp service using aluminum wiring, the recommended size is 2 AWG aluminum wire. Aluminum has a higher resistance than copper, so it needs to be one size larger than copper to carry the same amperage. The thicker 2 AWG aluminum wire has an ampacity matching that of 3/0 copper for a 100 amp panel. It’s important to use corrosion inhibitors and proper connections when wiring with aluminum.

Copper Wire Size for 100 Amp Service

The most common wire size used for both main and sub 100 amp panels is 3/0 AWG copper wire. This 100 amp rated wire has a temperature rating of 90°C and insulation like THHN that allows it to handle sustained 100 amp currents. Copper is the preferred wiring material due to its conductivity, safety, and durability. Using the proper 3/0 AWG 100a copper wire size for a 100 amp service ensures protection and performance.

Wire Size for 100 Amp Breaker

For circuits controlled by a 100 amp breaker in the main or sub panel, the minimum wire size is #3 AWG copper wire. This size 100 amp breaker wire accommodates the high current that can be drawn through a 100 amp circuit breaker. A #3 AWG wire feeds electricity reliably and safely for loads protected by a 100A breaker. Though more expensive than smaller wires, it meets code requirements.

Ground Wire Size for 100 Amp Service

For an effective grounding system in a 100 amp service, the recommended ground wire size is #4 AWG copper wire. This satisfies NEC requirements for proper grounding of a 100A electrical service. Using #4 AWG for the ground wire rather than a smaller gauge provides very low impedance and ensures faults or overloads will be properly cleared. A thicker ground wire also improves safety against electric shock hazards.


When wiring a 100 amp residential or commercial electrical service, following the standard wire size recommendations is crucial for safety and performance. The proper wire gauges take into account the amperage rating, allowable temperature rise, and other factors. Using the correct 3/0 AWG copper wires for the main and sub panels, #3 AWG for 100 amp circuits, and #4 AWG for equipment grounding conductors ensures a compliant, quality 100 amp installation.

Published On: 2023年11月8日Categories: ,