What size ground wire for a 100 amp service?

Two different grounds. The grounding electrode conductor to the ground rods or Ufer is sized from the service conductors (NEC Table 250.66): with 4 AWG copper service conductors it is 8 AWG copper, and the same 8 AWG copper with 2 AWG aluminum. If this is a 100 A feeder to a subpanel instead, its equipment grounding conductor is 8 AWG copper or 6 AWG aluminum (NEC Table 250.122).

Can I use aluminum wire on a 100 amp service?

Yes, 2 AWG aluminum for a dwelling service (1 AWG for a general feeder) is code-compliant. Aluminum is standard for services and large feeders because it costs far less; use connectors rated AL/CU and anti-oxidant compound where required. For 15-20 A branch circuits, stick with copper.

Is 100 amps enough for a house?

A 100 A service handles a small-to-mid-size home, but adding an EV charger, heat pump, or electric range can push it to its limit: a load calculation (NEC 220) tells you for sure. Try our home electrical load calculator.

What Size Wire for a 100 Amp Service?

Q: How far can I run 3 AWG copper on 100 amps?

Ampacity doesn't change with distance, but voltage drop does. Keeping drop under the recommended 3% at a 80 A load (80% of the breaker), 3 AWG copper is good for roughly 183 ft one-way at 240 V. Past that, step up a gauge: use our voltage drop calculator for your exact run.

For a 100 A single-phase dwelling service, the NEC allows 4 AWG copper or 2 AWG aluminum (310.12 83% rule). A general 100 A feeder sized from Table 310.16 needs 3 AWG copper / 1 AWG aluminum.

Minimum wire size for 100 amps

Application	Copper (75°C)	Aluminum (75°C)
Branch circuit / feeder (Table 310.16)	3 AWG	1 AWG
Dwelling service / main feeder (310.12)	4 AWG	2 AWG

Assumes 75°C-rated terminations (NEC 110.14(C)). Both assume no more than three current-carrying conductors in a raceway at 30°C ambient. Derating, continuous loads, and local amendments can change the answer: confirm with a licensed electrician.

Ground wire for 100 amps

Ground	Copper	Aluminum
Equipment ground, 100 A feeder to a subpanel (Table 250.122)	8 AWG	6 AWG
Electrode conductor, 4 AWG Cu service (Table 250.66)	8 AWG	6 AWG
Electrode conductor, 2 AWG Al service (Table 250.66)	8 AWG	6 AWG

The electrode conductor runs from the service to the ground rods, Ufer or water pipe; to rods alone it never has to exceed 6 AWG copper (NEC 250.66(A)), and aluminum may not terminate within 18 in of the earth (NEC 250.64(A)). The equipment ground applies when the same rating feeds a subpanel. Every size, with a worked upsizing example, is in the ground wire size chart.

How far can you run it? (voltage drop)

Keeping voltage drop under the recommended 3% at a 80 A load (80% of the breaker), 3 AWG copper is good for roughly:

System voltage	Max one-way run (3 AWG Cu)
240 V	≈ 183 ft

Past these distances, step up one gauge. Run your exact length and load through the voltage drop calculator.

What runs on 100 amps

Main service (older/smaller homes)
Detached garage / ADU subpanel

Parts for a 100 A service

Since the 2020 NEC (230.67), a new or replaced dwelling service must have surge protection: a Type 2 SPD at the panel is how most 100 A services meet it.

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Type 2 whole-house SPD

Siemens BoltShield FSPD140

Best for: The default whole-house pick on any brand of panel

Check price on Amazon(paid link)

Non-contact voltage tester

Klein Tools NCVT-3P

Best for: Confirming a circuit is dead before you open a device or box

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All surge protector picks

Frequently asked questions

For a 100 A single-phase dwelling service or main feeder, the NEC 310.12 rule allows 4 AWG copper or 2 AWG aluminum. A general (non-dwelling-service) 100 A feeder sized from Table 310.16 needs 3 AWG copper or 1 AWG aluminum at 75°C.

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What Size Wire for a 100 Amp Service?

Minimum wire size for 100 amps

Ground wire for 100 amps

How far can you run it? (voltage drop)

What runs on 100 amps

Parts for a 100 A service

Siemens BoltShield FSPD140

Klein Tools NCVT-3P

Frequently asked questions

What size wire do I need for a 100 amp service?

What size ground wire for a 100 amp service?

Can I use aluminum wire on a 100 amp service?

How far can I run 3 AWG copper on 100 amps?

Is 100 amps enough for a house?

Other amperages