What Size Wire for 150 Amps?
Short answer: a 150 amp dwelling service or main feeder uses 1 AWG copper or 2/0 AWG aluminum (NEC Table 310.12). A 150 amp subpanel feeder or non-dwelling service uses 1/0 AWG copper or 3/0 AWG aluminum (Table 310.16, 75°C). The equipment ground for a 150 A feeder is 6 AWG copper or 4 AWG aluminum.
150 A conductor sizes
| Application | Copper | Aluminum |
|---|---|---|
| Dwelling service / main feeder (310.12) | 1 AWG | 2/0 AWG |
| Subpanel feeder or non-dwelling (310.16, 75°C) | 1/0 AWG | 3/0 AWG |
The service sizes come from the 83% allowance: 150 × 0.83 = 124.5 A. At 75°C, 1 AWG copper (130 A) and 2/0 aluminum (135 A) meet it; 2 AWG copper (115 A) and 1/0 aluminum (120 A) do not. A subpanel feeder must carry the full 150 A, which takes 1/0 copper (150 A) or 3/0 aluminum (155 A). Full columns are in the ampacity chart.
Grounding
- GEC (Table 250.66): with 1 or 1/0 copper, or 2/0 or 3/0 aluminum service conductors, the GEC is 6 AWG copper or 4 AWG aluminum.
- EGC for a 150 A feeder: 6 AWG copper or 4 AWG aluminum (Table 250.122).
- Upsized feeders need upsized grounds. When the hots are increased for voltage drop, 250.122(B) requires the EGC to grow by the same circular-mil ratio (see the example below).
150 A feeder by distance (240 V)
| Conductor | 50 ft | 100 ft | 150 ft | 200 ft |
|---|---|---|---|---|
| Copper | 1/0 AWG (0.6%) | 1/0 AWG (1.2%) | 1/0 AWG (1.8%) | 1/0 AWG (2.4%) |
| Aluminum | 3/0 AWG (0.6%) | 3/0 AWG (1.3%) | 3/0 AWG (1.9%) | 3/0 AWG (2.5%) |
Smallest conductor that meets both the 75°C ampacity for a 150 A circuit and a 3% voltage drop at 120 A (80% of the rating), 240 V single-phase, one-way distance. Percent drop in brackets. If the circuit uses NM-B cable or 60°C terminations, start from the 60°C column instead.
Conduit size for 150 A
- Service, three 1 AWG copper THHN: 3 × 0.1562 = 0.4686 in², which fits 1-¼" EMT or PVC Schedule 40.
- Subpanel feeder, three 1/0 copper THHN plus a 6 AWG ground: 3 × 0.1855 + 0.0507 = 0.6072 in². That misses 1-¼" EMT by 0.0088 in², so it needs 1-½" EMT or PVC.
- Aluminum 2/0 or 3/0 XHHW-2: take the conductor areas from Chapter 9 Table 5 and run the same 40% check with the conduit fill chart.
Worked example: 150 A feeder to a pole barn, 250 feet
A 150 A feeder runs 250 feet to a pole barn with an expected load of 120 A.
- Ampacity minimum: 1/0 copper or 3/0 aluminum.
- Voltage drop, 1/0 copper: 2 × 12.9 × 120 × 250 ÷ 105,600 = 7.33 V, or 3.1%. Just over the guideline.
- Upsize to 2/0 copper: 2 × 12.9 × 120 × 250 ÷ 133,100 = 5.82 V, or 2.4%. For aluminum, 3/0 gives 7.58 V; 4/0 gives 6.01 V, or 2.5%.
- Increase the EGC (250.122(B)): 2/0 has 133,100 ÷ 105,600 = 1.26 times the area of 1/0. The 6 AWG copper ground becomes 26,240 × 1.26 = about 33,073 circular mils, which rounds up to 4 AWG copper (41,740 cmil).
Size the load with the load calculator first, then check voltage drop; long agricultural feeders are where both matter.
Lugs, cable types and upsizing
Check the lug range before you upsize. A 150 A panel's main lugs or main breaker are listed for a range of conductor sizes, printed on the label, and a conductor increased for voltage drop may not fit. The fix is a listed splice or reducing connector in a junction box or gutter, never trimming strands. For services, 2/0 aluminum SEU or SER is the common cable; SER carries an insulated neutral and is the one to use when the run continues as a four-wire feeder. Some electricians run 4/0 aluminum on a 150 A service so the conductors are already sized for a future 200 A upgrade, provided the meter base and panel lugs accept it.
When 150 A makes sense
150 A services are common in mid-size homes with some electric appliances and in service upgrades where the utility or the existing meter base limits the size. With heat pumps and EV charging becoming standard, many electricians now skip 150 A and go straight to 200 A, since the difference in equipment cost is small compared to the labor of doing the upgrade twice. See 200 amp service wire size.
Common mistakes inspectors flag
- 2/0 aluminum on a 150 A subpanel breaker without a load calculation (see the FAQ below).
- Leaving the EGC at 6 AWG after upsizing the hots for distance.
- Service conductor sizes used for a feeder to an outbuilding.
Frequently asked questions
Is 2/0 aluminum good for 150 amps?
Yes for a dwelling service or main feeder under Table 310.12. For a subpanel feeder, 2/0 aluminum is rated 135 A at 75°C, so a 150 A feeder needs 3/0 aluminum, unless 240.4(B) applies: 135 A isn't a standard breaker size, so a 150 A breaker is permitted when the calculated load is 135 A or less.
What size copper wire for a 150 amp subpanel?
1/0 AWG copper (150 A at 75°C).
Can I use 4/0 aluminum on a 150 amp service?
Yes. Larger conductors are always allowed on a smaller breaker, as long as they fit the listed lug range. It costs more material now but can save pulling new service conductors later.
What's the difference between 125 A and 150 A wire?
One size up on each: a 125 A dwelling service is 2 AWG copper or 1/0 aluminum, and a 150 A service is 1 AWG copper or 2/0 aluminum. See 125 amp wire size.
Last updated: October 6, 2026. Based on NEC 2023. Check results against the code edition and local amendments your jurisdiction enforces and with the AHJ; electrical work should be done by qualified people.