A 200 amp home service usually takes 2/0 AWG copper or 4/0 AWG aluminum; a non-dwelling 200A feeder needs 3/0 copper or 250 kcmil aluminum.
Two code rules cover a 200 amp service, and swapping them causes failed inspections. NEC Table 310.12 sizes a one-family home’s service entrance. NEC Table 310.16 sizes a general feeder. Both carry 200 amps on paper but call for different copper.
The dwelling rule sizes conductors for just 83% of the service rating — 166 amps on a 200 amp service — which is why 2/0 copper and 4/0 aluminum land on residential plans instead of the heavier 3/0 and 250 kcmil a commercial feeder needs.
Sizing A 200 Amp Service: Which Code Rule Applies
NEC Table 310.12, the dwelling-service allowance, covers a single dwelling unit’s service entrance at 2/0 AWG copper or 4/0 AWG aluminum for 200 amps.
The dwelling allowance uses 83% of the service rating, so 200 amps shrinks to a 166 amp minimum.
The key word is “dwelling” — the allowance belongs to the home’s service entrance, not every 200 amp circuit leaving the panel. A subpanel feed, detached shop, or commercial 200 amp feeder is a feeder, sized from Table 310.16. A wire size guide for a 200 amp service lays both rules side by side.
| Installation | Copper Conductor | Aluminum Conductor |
|---|---|---|
| 200A dwelling service entrance (Table 310.12) | 2/0 AWG | 4/0 AWG |
| 200A general feeder (Table 310.16, 75°C) | 3/0 AWG | 250 kcmil |
| Ampacity of the dwelling sizes at 75°C | 175A for 2/0 | 180A for 4/0 |
| Ampacity of the feeder sizes at 75°C | 200A for 3/0 | 205A for 250 kcmil |
| Minimum ampacity a 200A dwelling service requires | 166A | 166A |
| Termination temperature assumed above | 75°C | 75°C |
| Runs well beyond average length | Upsize for voltage drop | Upsize for voltage drop |
Copper Or Aluminum: Where Each One Fits
Copper and aluminum both reach 200 amps, so the choice comes down to price, weight, and terminations. Aluminum is lighter and cheaper for the same run; copper gives a smaller conductor for the same ampacity.
The ampacities above sit in the 75°C column and only hold when terminations are rated 75°C. Lower-rated lugs force a larger conductor, a common oversight. Read the equipment label before buying cable.
Aluminum asks more of the installer: lugs must be listed for aluminum, and cable terminated per manufacturer specs. In a home’s service entrance that’s routine, and 4/0 aluminum is standard at 200 amps. The same metal in a general feeder is held to 250 kcmil instead.
Four mix-ups account for most bad sizing:
- Borrowing the dwelling allowance for a non-dwelling feeder or subpanel.
- Reading an ampacity off Table 310.16 and calling it the dwelling answer.
- Picking a conductor from the wrong temperature column at the terminations.
- Leaving voltage drop out of the plan on a long run.
Pricing the run usually settles the metal, and the tested 200 amp service cable roundup compares copper and aluminum options by installation.
Does Voltage Drop Force A Bigger Wire On Long Runs?
Yes — a long run can call for a conductor larger than the code minimum, because ampacity tables protect the wire from overheating, not the equipment from low voltage. How far you upsize depends on distance and load.
A detached garage or shop a couple hundred feet from the main panel is the classic case. The conductor has to be big enough for the amperage, then may need to go up one or two trade sizes so voltage at the far end stays workable. Treat the standard dwelling sizes as a floor, not a universal answer.
Three checks settle most 200 amp jobs:
- Match the rule to the installation — a dwelling service entrance follows Table 310.12, while a subpanel or feeder follows Table 310.16.
- Confirm the termination temperature rating and that lugs are listed for the metal you picked.
- Check run length for voltage drop before ordering cable, then confirm the final size with your local inspector.
When those three line up, the conductor you land on will pass inspection without a second trip.
FAQs
Does The Dwelling Rule Apply To A Detached Garage?
No. The dwelling allowance covers the home’s service entrance, not a feeder leaving the panel for another structure. A detached garage, shop, or outbuilding is fed by a feeder, and a 200 amp feeder is sized from Table 310.16 — 3/0 copper or 250 kcmil aluminum at 75°C.
Why Does Aluminum Need A Bigger Size Than Copper?
Aluminum carries less current for a given cross-section than copper, so matching ampacity takes more metal. That’s why a dwelling service pairs 2/0 AWG copper with 4/0 AWG aluminum, and the general feeder sizes run 3/0 copper against 250 kcmil aluminum. Aluminum also needs lugs listed for it.
Is 2/0 Copper Always Enough At 200 Amps?
Only on a dwelling service entrance. Feed a subpanel or commercial feeder at 200 amps and that conductor is undersized, so the job needs 3/0 copper or 250 kcmil aluminum instead.
References & Sources
- Galvin Power. “What Size Wire for 200 Amp Service” Supports the dwelling-service versus general feeder sizing comparison and the 75°C ampacity figures.
