3/0 AWG Wire: Ampacity, Uses & Specs
NEC Table 310.16 ampacity for 3/0 copper and aluminum service, feeder, and 200-amp panel wiring.
3/0 AWG wire is used for 200 A residential service entrance (aluminum), 225 A subpanel feeders (copper), commercial solar AC combiner-to-panel runs, battery bank main interconnect cables, and small commercial main feeders. It carries 225 A at 75°C copper and 175 A at 75°C aluminum under NEC Table 310.16, making it a workhorse conductor for large residential and small commercial services and feeders.
3/0 AWG wire has a cross-sectional area of 167.8 kcmil (85.03 mm²) with a conductor diameter of 0.4096 inches (10.4 mm). The copper weight is approximately 508.5 lbs per 1,000 feet, with a DC resistance of 0.0766 Ω/1,000 ft for copper and 0.126 Ω/1,000 ft for aluminum at 75°C.
The physical dimensions of 3/0 AWG are defined by NEC Chapter 9, Table 8. These values are used for conduit fill calculations (NEC Chapter 9, Table 4), voltage-drop math, and mechanical connector sizing.
| Specification | Copper (Cu) | Aluminum (Al) |
|---|---|---|
| AWG Size | 3/0 | 3/0 |
| Area (kcmil) | 167.8 | 167.8 |
| Area (mm²) | 85.03 | 85.03 |
| Diameter (in) | 0.4096 | 0.4096 |
| Diameter (mm) | 10.4 | 10.4 |
| DC Resistance @ 75°C (Ω/1000ft) | 0.0766 | 0.126 |
| Weight (lbs/1000 ft) | 508.5 | 154.08 |
| 60°C ampacity (A) | 200 | 155 |
| 75°C ampacity (A) | 225 | 175 |
| 90°C ampacity (A) | 260 | 205 |
NEC Table 310.16 ampacity for 3/0 AWG copper conductors in raceway, cable, or earth (not more than three current-carrying conductors), based on 30°C (86°F) ambient. Termination temperature ratings (NEC 110.14(C)) apply — most 100 A and smaller equipment is rated 60°C; most 100 A+ equipment is rated 75°C.
| Insulation Type | Temp Rating | Ampacity | Common Use |
|---|---|---|---|
| TW, UF | 60°C | 200 A | Direct-burial UF cable, wet locations, older wiring |
| RHW, THW, THWN, USE, XHHW (wet) | 75°C | 225 A | Panel feeders, service conductors, wet-rated raceway |
| THHN, XHHW-2, RHW-2, USE-2, RHH | 90°C | 260 A | Dry raceway, derating base ampacity, high-temp motors |
3/0 AWG Aluminum Ampacity
NEC Table 310.16 ampacity for 3/0 AWG aluminum and copper-clad aluminum conductors. Aluminum ampacity is roughly 78% of copper for the same size. Do not use aluminum smaller than 6 AWG on general-purpose branch circuits.
| Insulation Type | Temp Rating | Ampacity |
|---|---|---|
| TW, UF | 60°C | 155 A |
| RHW, THW, THWN, USE, XHHW (wet) | 75°C | 175 A |
| THHN, XHHW-2, RHW-2, USE-2, RHH | 90°C | 205 A |
3/0 AWG is common in medium-scale commercial PV: 200-250 A inverter AC output combines, 200 A battery inverter DC feeders, and combined-inverter tie-in feeders to the utility disconnect.
For a code-compliant solar PV installation using 3/0 AWG, apply the 125% continuous-load factor from NEC 690.8(B): the maximum continuous inverter output current must not exceed 180 A at 75°C copper terminations. Battery DC circuits under NEC 690.31(A) require the same 125% continuous-load derating.
Typical applications for 3/0 AWG wire
| Application | Typical Load | Notes |
|---|---|---|
| 200 A residential service | 200 A continuous | 3/0 aluminum SER cable (NEC 310.12 residential rule) |
| 225 A subpanel feeder | 225 A | 3/0 THHN/THWN copper in raceway |
| Commercial solar AC combiner | 200 A per inverter | Between combiner and MDP for 100-125 kW inverter |
| Battery bank main interconnect | 200-260 A | Copper welding cable or Class B for 48 V ESS |
| EV DC fast charger service | 200 A | Feeder to 150 kW DCFC service disconnect |
| Motor branch circuit | 160-200 A FLA | Large industrial motor at 480 V (NEC 430) |
Installing 3/0 AWG wire correctly requires attention to termination temperature ratings, conduit fill, bending radius, and NEC 110.14 lug torque specifications. Miswiring at these points is the leading cause of thermal failures and permit rejections.
Verify termination temperature rating
at both ends (NEC 110.14(C)) — most 100 A+ gear is 75°C; you must use the 75°C column ampacity for 3/0 AWG.
Select insulation for the environment
THHN/THWN-2 covers most raceway installs; USE-2 or RHW-2 for direct-buried; PV wire for exposed solar DC runs.
Verify conduit fill
for three 3/0 AWG THHN conductors, use NEC Chapter 9 Table 4 fill percentage (40% for over-2-conductor).
Apply derating factors
NEC 310.15(B) ambient temperature correction if above 30°C, and 310.15(C) adjustment for more than 3 current-carrying conductors in the raceway.
Torque lugs to manufacturer spec
typically 275-500 in-lb for 3/0 AWG compression lugs; always use a calibrated torque wrench per NEC 110.14(D).
Support in vertical raceway
NEC 300.19 requires cable supports at maximum intervals; 3/0 AWG vertical support interval per Table 300.19.
Label the conductors
phase colors black/red/blue for 120/208 V, brown/orange/yellow for 277/480 V (NEC 200.6, 210.5).
NEC 210.19(A) FPN No. 4 recommends limiting branch-circuit voltage drop to 3% and total feeder + branch drop to 5%. Use the formula:
VD = (2 × K × I × L) / CM
- K = 12.9 for copper, 21.2 for aluminum (Ω-cmil/ft at 75°C)
- I = load current in amps
- L = one-way distance in feet
- CM = 167800 for 3/0 AWG
Voltage drop reference — 3/0 AWG copper at various loads/distances
| Load (A) | 50 ft | 100 ft | 200 ft | 300 ft |
|---|---|---|---|---|
| 56 A | 0.18% | 0.36% | 0.72% | 1.08% |
| 112 A | 0.36% | 0.72% | 1.44% | 2.15% |
| 168 A | 0.54% | 1.08% | 2.15% | 3.23% |
| 225 A | 0.72% | 1.44% | 2.88% | 4.32% |
Values shown for 240 V single-phase copper. Green = under 3% (branch circuit target). Yellow = between 3% and 5% (feeder acceptable but tight). Red = exceeds 5% total drop limit — upsize the conductor.
| NEC Article | What it Covers |
|---|---|
| NEC 110.14(C) | Termination temperature rating limitations |
| NEC 240.4 | Overcurrent protection of conductors |
| NEC 310.12 | Single-phase dwelling services (aluminum 3/0 for 200 A) |
| NEC 310.15(B) | Ambient temperature correction factors |
| NEC 310.15(C) | Adjustment for more than 3 current-carrying conductors |
| NEC 310.16 | Ampacities for insulated conductors — 3/0 AWG in this table |
| NEC Ch 9, Table 4 | Conduit fill percentages |
| NEC Ch 9, Table 5 | Cross-sectional area of 3/0 AWG conductor with insulation |
| NEC Ch 9, Table 8 | Bare-conductor properties |
| NEC Ch 9, Table 9 | AC resistance and reactance for cables in conduit |
PES Supply stocks 3/0 AWG in THHN, THWN-2, XHHW-2, and USE-2 insulations in both copper and aluminum. All conductors are UL Listed and manufactured to NEC and ASTM specifications. Explore our full wire and cable collection or view the master NEC ampacity chart for all wire gauges.
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What is 3/0 AWG wire used for?
3/0 AWG is used for 200 A residential service entrance (aluminum), 225 A subpanel feeders (copper), commercial solar AC combiner-to-panel runs, battery bank main interconnect cables, and small commercial main feeders. It is one of the most common conductors for 200 A residential service entrance (aluminum SER cable) and 225 A commercial subpanel feeders (copper THHN).
What is the ampacity of 3/0 copper?
NEC Table 310.16 rates 3/0 AWG copper at 200 A (60°C), 225 A (75°C), and 260 A (90°C). Most 100 A+ equipment uses 75°C terminations, so the effective rating is 225 A.
What is the ampacity of 3/0 aluminum?
NEC Table 310.16 rates 3/0 AWG aluminum at 155 A (60°C), 175 A (75°C), and 205 A (90°C). Under NEC 310.12 (dwelling services), 3/0 aluminum can serve up to 200 A on a single-phase residential service.
Can 3/0 aluminum handle a 200 A service?
Yes, only for single-phase 3-wire dwelling services under NEC 310.12. Table 310.12(A) explicitly permits 3/0 aluminum or copper-clad aluminum SER cable for a 200 A residential service. In commercial applications, use Table 310.16 (175 A at 75°C) — you would need 4/0 aluminum instead.
What size conduit for 3 x 3/0 THHN copper?
Three 3/0 AWG THHN copper conductors need a minimum 2-inch trade-size EMT or rigid conduit per NEC Chapter 9 Table 4 (40% fill). With a grounding conductor added, verify against Chapter 9 Table 5.
Is 3/0 copper cheaper than 4/0 aluminum?
For the same ampacity, 4/0 aluminum (180 A at 75°C) roughly matches 3/0 copper (225 A at 75°C) at about 30-40% of the copper material cost. However, aluminum requires anti-oxidant compound at every termination and larger conduit, so total installed cost is often only 15-25% cheaper.
How much does 3/0 copper weigh?
3/0 AWG bare copper weighs 508.5 lbs per 1,000 feet. A 500-foot reel of 3/0 THHN weighs approximately 275 lbs — plan for a wire cart or two-person lift.
What torque spec for 3/0 lugs?
3/0 AWG compression lugs typically require 275-375 in-lb (23-31 ft-lb) depending on manufacturer. Always verify with the lug or terminal manual and use a calibrated torque wrench per NEC 110.14(D).
Can I use 3/0 for a subpanel feed?
Yes. 3/0 copper at 225 A (75°C) is standard for a 225 A subpanel. 3/0 aluminum at 175 A serves a 175 A subpanel. Do not exceed the ampacity of the smallest link — verify lugs, breakers, and cable are all rated for the intended current.
- Complete NEC Wire Ampacity Chart — full table for all AWG and MCM sizes
- Wire & Cable Collection — shop THHN, THWN, XHHW, USE, and PV wire
- 2/0 AWG Wire Specs
- 4/0 AWG Wire Specs
- 6 AWG Wire Specs
- 8 AWG Wire Specs
- 10 AWG Wire Specs
- 12 AWG Wire Specs
- 14 AWG Wire Specs
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