What Size Wire for a 175 Amp Service?
Verified against NEC 2023, checked against the 2026 edition · Last checked August 18, 2026
A 175 amp one-family dwelling service takes 1/0 AWG copper or 3/0 AWG aluminum service conductors. The 83% rule of 310.12 applies: 175 A × 0.83 = 145.25 A of required ampacity, read from the 75°C column of Table 310.16.
The 83% rule covers the service and a feeder carrying the entire dwelling load · 310.12. Feeding equipment or a regular sub panel? Use the full sizes: wire size for a 175 amp breaker.
| Conductor | Size | Usable | Basis |
|---|---|---|---|
| Copper · 75°C terminals | 1/0 AWG | 150 A | Table 310.16 · 75°C column |
| Aluminum · 75°C terminals | 3/0 AWG | 155 A | Table 310.16 · 75°C column |
| Grounding electrode conductor | 6 AWG Cu or 4 AWG Al | Table 250.66 |
GEC row applies to the copper service size shown. Aluminum service conductors can require a different GEC row per Table 250.66. Rod electrodes cap at 6 AWG Cu · 250.66(A).
What changes this answer
More than 3 conductors · 310.15(C)(1)
Four or more current-carrying conductors in one raceway derate ampacity by 20% or more. Run the calculator with your count.
Hot locations · 310.15(B)(1)
Ambient above 86°F cuts ampacity. Attics and rooftop conduit routinely trigger this correction.
Long runs and voltage drop
Distance does not change the NEC minimum, but past roughly 100 feet voltage drop usually forces a larger conductor.
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Common questions
- What size wire do I need for a 175 amp service?
- 1/0 AWG copper or 3/0 AWG aluminum for a one-family dwelling service, per the 83% rule of NEC 310.12 and Table 310.16.
- Why is 1/0 AWG copper allowed on a 175 amp service?
- NEC 310.12 lets the service conductors of a one-family dwelling carry 83% of the service rating, because the full calculated load rarely lands on the service continuously. 175 A × 0.83 = 145.25 A.
- What size grounding electrode conductor for a 175 amp service?
- 6 AWG copper or 4 AWG aluminum, from Table 250.66 for 1/0 AWG copper service conductors. A rod electrode never needs larger than 6 AWG copper · 250.66(A).
- Does the 83% rule apply to a detached garage or a sub panel?
- Only to the service and to a feeder that carries the entire dwelling load · 310.12. A regular feeder or branch circuit is sized at 100%.