| Item | Value |
|---|---|
| Breaker type | Double-pole, 240 V |
| Recommended copper conductor | 3/0 AWG (2/0 on a dwelling service, NEC 310.12) |
| Recommended aluminum conductor | 250 kcmil (4/0 AWG on a dwelling service, NEC 310.12) |
| Minimum per NEC Table 310.16, 75°C | 3/0 AWG copper (200 A) |
| Minimum NM-B cable, 60°C column | Not available: NM-B is made only in 14–2 AWG copper (NEC 334.104). Use SER cable or THHN in conduit. |
| Equipment grounding conductor | 6 AWG copper / 4 AWG aluminum (NEC Table 250.122) |
| Maximum continuous load (125% rule) | 160 A |
| Maximum non-continuous load | 200 A |
Standard main service for a modern single-family home, large sub-panels, whole-house transfer switches
| Load | Notes |
|---|---|
| Main residential service | The current standard for new construction |
| Whole-house generator transfer switch | Rated to match the service |
| Large sub-panel feed | Detached structures with heavy load |
| Load centre for all-electric homes | Heat pump plus EV plus induction |
For a general 200 A feeder, Table 310.16 requires 3/0 copper (200 A) or 250 kcmil aluminum (205 A). For a dwelling service or a feeder carrying the entire dwelling load, NEC 310.12 allows 83% sizing, which is why 2/0 copper or 4/0 aluminum is the near-universal choice for a 200 A house service. Confirm which rule applies before buying wire — the difference is substantial.
Service and feeder conductors do not require GFCI. A 200 A service requires a grounding electrode system per NEC 250.50, with the grounding electrode conductor sized from Table 250.66 — 4 AWG copper for 2/0 service conductors, or 6 AWG where ground rods are the only electrode.
| One-way run | Drop | % of 240V | Verdict |
|---|---|---|---|
| 25 ft | 0.77 V | 0.3% | Within the 3% branch-circuit target |
| 50 ft | 1.53 V | 0.6% | Within the 3% branch-circuit target |
| 75 ft | 2.30 V | 1.0% | Within the 3% branch-circuit target |
| 100 ft | 3.06 V | 1.3% | Within the 3% branch-circuit target |
| 150 ft | 4.60 V | 1.9% | Within the 3% branch-circuit target |
| 200 ft | 6.13 V | 2.6% | Within the 3% branch-circuit target |
The 80% rule: a continuous load is one expected to run for three hours or more — EV chargers, electric heat, and most commercial lighting. NEC 210.20(A) requires the overcurrent device to be rated at not less than 125% of that continuous load, which leaves 160 A usable on a 200 A breaker. A breaker that trips after an hour or two under a steady load is usually a continuous-load sizing mistake, not a faulty breaker.
Under NEC Table 310.16 at 75°C, 3/0 AWG copper (200 A) or 250 kcmil aluminum (205 A). For a one-family dwelling service or main power feeder, NEC 310.12 allows 83% sizing (166 A): 2/0 copper or 4/0 aluminum. The equipment grounding conductor is 6 AWG copper per NEC Table 250.122.
160 amps. NEC 210.19(A)(1) and 210.20(A) require the circuit to be rated at 125% of a continuous load — one that runs for three hours or more — which works out to 80% of the breaker rating available for continuous use. Non-continuous loads may use the full 200 A.
6 AWG copper or 4 AWG aluminum, from NEC Table 250.122. The table lists maximum overcurrent device ratings, so you round up to the next listed row. If the circuit conductors are upsized for voltage drop, NEC 250.122(B) requires the ground to be upsized proportionally too.
No. NEC 334.80 limits NM-B to the 60°C column of Table 310.16, which would require 250 kcmil copper for 200 A, but NM-B is only manufactured in 14 through 2 AWG copper (NEC 334.104). Use SER cable or THHN/THWN-2 in conduit, sized from the 75°C column: 3/0 AWG copper.