What size wire do I need for a 200 amp breaker?

4/0 AWG copper or 4/0 AWG aluminum, per NEC Table 310.16 at the 75°C column. The equipment grounding conductor is 6 AWG copper per NEC Table 250.122.

What is the maximum continuous load on a 200 amp breaker?

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.

What size ground wire for a 200 amp breaker?

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.

Can I use 250 kcmil AWG NM-B cable on a 200 amp breaker?

Yes. NEC 334.80 requires NM-B ampacity to be taken from the 60°C column of Table 310.16, where 250 kcmil AWG copper is rated 215 A. That is why NM-B sometimes needs a larger conductor than THHN in conduit for the same breaker.

200 Amp Breaker Wire Size

Copper Wire

4/0 AWG

Aluminum Wire

4/0 AWG

Ground (Copper)

6 AWG

Double-pole · 240 V · Max continuous load 160 A · NEC Tables 310.16 and 250.122

200 Amp Circuit — Specification Summary

Item	Value
Breaker type	Double-pole, 240 V
Recommended copper conductor	4/0 AWG
Recommended aluminum conductor	4/0 AWG
Minimum per NEC Table 310.16, 75°C	3/0 AWG copper (200 A)
Minimum NM-B cable, 60°C column	250 kcmil AWG copper (215 A)
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

Recommended conductor sizes follow the 75°C column of NEC Table 310.16, the column that matches the termination rating of virtually all modern breakers and lugs (NEC 110.14(C)).

Common Uses for 200 A Circuits

Standard main service for a modern single-family home, large sub-panels, whole-house transfer switches

What a 200 Amp Breaker Powers

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

Always size a circuit from the equipment nameplate or a load calculation, not from a general table. Air conditioners and heat pumps in particular carry a minimum circuit ampacity (MCA) and maximum overcurrent protective device (MOCP) rating that override the general rules.

NEC requirements for this circuit

For a general 200 A feeder, Table 310.16 requires 4/0 copper (230 A) or 250 kcmil aluminum. 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.

Voltage Drop by Distance — 4/0 AWG Copper at 200 A

One-way run	Drop	% of 240V	Verdict
25 ft	0.61 V	0.3%	Within the 3% branch-circuit target
50 ft	1.22 V	0.5%	Within the 3% branch-circuit target
75 ft	1.82 V	0.8%	Within the 3% branch-circuit target
100 ft	2.43 V	1.0%	Within the 3% branch-circuit target
150 ft	3.65 V	1.5%	Within the 3% branch-circuit target
200 ft	4.86 V	2.0%	Within the 3% branch-circuit target

Single-phase, 240V, full 200 A load, 0.0608 Ω/1000 ft DC resistance (NEC Chapter 9, Table 8) at 75°C terminations. NEC 210.19(A) Informational Note recommends keeping branch-circuit drop at or below 3%, and 5% total across feeder plus branch circuit. See the voltage drop formula for the arithmetic.

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.

Other Breaker Sizes

15A 20A 30A 40A 50A 60A 100A 200A

Wire size for 200 amps — full page → 4/0 AWG full specifications → NEC Table 250.122 — ground wire size → NEC Table 310.16 — conductor ampacity → Wire size calculator →