200 amp wire size
A 200 amp dwelling service is usually wired with 4/0 AWG aluminum or 2/0 AWG copper, sized under NEC 310.12 at 83% of the rating. A 200 A feeder that is not the main dwelling service needs the full rating: 3/0 AWG copper or 250 kcmil aluminum in the 75 °C column.
Minimum wire size for 200 A
| Conductor | 60 °C column | 75 °C column |
|---|---|---|
| Copper | Not listed | 3/0 AWG |
| Aluminum | Not listed | 250 kcmil |
| Dwelling service, 83% (166 A) | — | 2/0 AWG Cu · 4/0 AWG Al |
Usually chosen: 4/0 AWG aluminum (often as 4/0-4/0-4/0-2/0 SER) or 2/0 AWG copper for a 200 A dwelling service; 3/0 copper or 250 kcmil aluminum for a full-rating 200 A feeder.
Breaker rating taken as the required ampacity; 240.4(D) limits applied. The charts list no 60 °C aluminum, and 60 °C copper only to 2 AWG (95 A), the largest NM-B. Manufacturer chart values (2017 NEC basis). Verify against the NEC edition adopted locally.
200 A is the standard service for new single-family houses. The difference between the two sizing rules matters most here, since 4/0 aluminum is the most familiar service conductor in residential work and yet is not a 200 A conductor in its own right.
Where 200 amp circuits are used
Most new houses get a 200 A service, and it is the usual target of upgrades from 100 A or 150 A, especially where heat pumps, electric ranges, hot tubs and EV chargers are added together. The service conductors run from the utility's point of connection to the meter base and on to the main disconnect.
200 A feeders appear where a meter-main combination outside feeds a 200 A panel inside, where a large house splits its load between two panels, and in light commercial work. In the meter-main case, the feeder to the inside panel carries the whole dwelling load, so the 83% rule can apply to it as well.
Dwelling services and main feeders: the 83% rule
NEC 310.12 permits service conductors, and feeder conductors that carry the entire load of a one-family dwelling or an individual dwelling unit, to have an ampacity of not less than 83% of a rating from 100 A to 400 A. The rule as written in the 2020 edition was checked for this page.
At 200 A, 83% is 166 A. In the 75 °C column, 2/0 copper at 175 A and 4/0 aluminum at 180 A are the smallest sizes that qualify; 3/0 aluminum, at 155 A, falls short. That is the origin of the 4/0 aluminum service.
Outside the rule, 4/0 aluminum is a 180 A conductor. On a 200 A subpanel feeder it may still be used under 240.4(B), since 180 A is not a standard rating, but only where the calculated load is 180 A or less.
Voltage drop at 200 A
3/0 copper at the full 200 A reaches 3% at about 234 ft at 240 V; 4/0 aluminum, whose resistance is about 30% higher, reaches it at roughly three-quarters of that distance. Long service laterals on rural property and feeders to distant outbuildings are where 250 kcmil or larger appears.
A service rarely carries 200 A for long, so a load-based drop calculation gives a lower figure than the table's full-rating values. Feeders to large, steady loads such as a shop with heat are better judged at full load.
| One-way length (ft) | Drop at 120 V (%) | Drop at 240 V (%) | Copper for 3% at 120 V | Copper for 3% at 240 V |
|---|---|---|---|---|
| 25 | 0.64 | 0.32 | 3/0 AWG | 3/0 AWG |
| 50 | 1.28 | 0.64 | 3/0 AWG | 3/0 AWG |
| 75 | 1.92 | 0.96 | 3/0 AWG | 3/0 AWG |
| 100 | 2.56 | 1.28 | 3/0 AWG | 3/0 AWG |
| 150 | 3.83 | 1.92 | 250 kcmil | 3/0 AWG |
| 200 | 5.11 | 2.56 | 300 kcmil | 3/0 AWG |
| 250 | 6.39 | 3.19 | 500 kcmil | 4/0 AWG |
| 300 | 7.67 | 3.83 | 500 kcmil | 250 kcmil |
Full rating on a single-phase circuit, copper at 75 °C, stranded.
Breaker pairing
A 200 A main breaker or two-pole feeder breaker protects the conductors. The 83% rule for dwelling services and the next-size-up rule of 240.4(B) are separate; the first sizes the service conductors directly, the second allows a conductor whose ampacity falls between standard ratings onto the next higher breaker.
2/0 copper at 175 A cannot use 240.4(B) on a 200 A breaker outside the 83% rule, because 175 A is a standard rating; it needs a 175 A breaker on a feeder that is not the dwelling's main feeder.
NM-B cable or THHN in conduit
200 A conductors are run as SER or SEU cable, as THHN/THWN-2 or XHHW-2 in conduit, or as USE-2 and URD underground. NM-B is not made in these sizes.
Overhead service-entrance conductors to a mast and conductors in a sunny conduit on the outside wall run hotter than 30 °C, and correction factors apply to them even under the 83% rule.
Copper or aluminum
Aluminum carries most 200 A services: 4/0 aluminum for a dwelling service and 250 kcmil aluminum for a full-rating feeder, against 2/0 and 3/0 copper. Meter bases and main breakers at this size are listed for aluminum as a matter of course.
Copper is chosen where conduit fill is tight or where the run is short and labor dominates the cost, since 2/0 copper is smaller and easier to bend than 4/0 aluminum.
Common mistakes
Treating 4/0 aluminum as a 200 A wire everywhere
4/0 aluminum is a 180 A conductor at 75 °C. It qualifies for 200 A only as a dwelling service or main feeder under 310.12, or under 240.4(B) with a load of 180 A or less.
Using 3/0 aluminum for a 200 A service
3/0 aluminum is rated 155 A, below the 166 A that 83% of 200 A requires. A 200 A service in aluminum starts at 4/0.
Sizing the neutral like the hots
The service neutral may be smaller than the phase conductors when the calculated unbalanced load allows, which is why SER is often sold as 4/0-4/0-4/0-2/0. It is not sized by the 83% rule.
Skipping the torque
Large aluminum lugs that are not torqued to the manufacturer's value loosen and overheat. 110.14(D) requires a calibrated torque tool where a value is marked.
Frequently asked questions
What size wire is needed for a 200 amp service?
For a dwelling service under NEC 310.12, the minimum is 2/0 AWG copper or 4/0 AWG aluminum, sized at 83% of 200 A. A 200 A circuit outside that rule needs 3/0 copper or 250 kcmil aluminum.
Is 4/0 aluminum good for 200 amps?
For a dwelling service or main feeder, yes, under the 83% rule. Otherwise 4/0 aluminum is rated 180 A at 75 °C and may be on a 200 A breaker only when the calculated load is 180 A or less.
What size wire is needed for a 200 amp subpanel?
3/0 AWG copper or 250 kcmil aluminum at the 75 °C column, unless the subpanel is fed from an outside meter-main and carries the whole dwelling load, where the 83% sizes apply.
Is 2/0 copper good for 200 amps?
For a dwelling service under NEC 310.12, yes. On other 200 A circuits 2/0 copper, rated 175 A, is undersized; 3/0 copper is the full-rating minimum.
What size ground wire is used for a 200 amp feeder?
Table 250.122 calls for a 6 AWG copper or 4 AWG aluminum equipment grounding conductor on a 200 A feeder. The grounding electrode conductor at the service is sized separately from Table 250.66.