For a 100 amp service, use #4 copper or #2 aluminum wire at minimum, sized to NEC Table 310.15(B)(16) for the conductor ampacity and terminal temperature rating.
What size copper wire do I need for 100 amp service?
If the run is long or the terminations are rated 60°C, bump up to #3 AWG copper. For a feeder to a subpanel, always use the 75°C column unless the equipment label says otherwise. Most modern breakers and panels accept 75°C wire—when in doubt, that’s your safest bet for future upgrades.
What wire size do I need to go 100 feet for a 100 amp service to a workshop?
Voltage drop becomes noticeable over 100 feet, so NEC 210.19(A) Informational Note 4 suggests keeping it under 3%. At 120V/240V, 3 AWG copper drops about 2.7% at full load; 1 AWG aluminum is roughly equivalent. If it’s in conduit or wet conditions, go with THHN/THWN-2 or XHHW-2 conductors. Don’t forget to check local amendments—some places require upsizing for workshops with heavy tools.
Can I run a 100 amp sub panel off 200 amp main?
Yes—you can install a 100 amp breaker in a 200 amp main panel.
The main panel’s bussing handles 200 amps, so a 100 amp breaker is perfectly fine. Just make sure the feeder conductors are sized for 100 amps using the 75°C column. Use a two-pole 100 amp breaker, #3 AWG copper or #1 AWG aluminum, and a separate neutral and ground bar in the subpanel. Label the feeder at both ends per NEC 408.4.
Will #2 wire fit in a 100 amp breaker?
#2 copper wire fits in a 100 amp breaker only if the terminations are rated 75°C.
#2 copper is rated 95 amps at 60°C and 115 amps at 75°C, but breakers are typically terminal-rated at 75°C. So yes, you can install #2 copper on a 100 amp breaker if the panel and breaker accept 75°C wire. When in doubt, upsize to #1 copper (110 amps at 60°C, 130 amps at 75°C).
Can you run a 100 amp sub panel off a 100 amp main panel?
Yes—you can run a 100 amp subpanel off a 100 amp main panel if the feeder and installation meet code.
NEC doesn’t forbid this, but you must use four-wire feeders (two hots, neutral, ground) and size conductors for 100 amps. Install a two-pole 100 amp breaker in the main, run #3 AWG copper or #1 AWG aluminum, and use a subpanel with separate neutral and ground bars. Just make sure the total load on the main panel doesn’t exceed 100 amps after adding the subpanel. Label everything clearly.
Can a 60 amp breaker feed a 100 amp sub panel?
Yes—you can feed a 100 amp subpanel with a 60 amp breaker, but the subpanel must be rated ≥60 amps.
The subpanel’s main breaker protects the internal bus, not the feeder rating. So a 100 amp subpanel can technically run on a 60 amp breaker—as long as the actual load stays under 60 amps. Size the feeder conductors to the breaker, like #6 AWG copper or #4 AWG aluminum for 60 amps. The subpanel’s main breaker is for protection, not capacity. Always do a load calculation before finalizing sizing.
What wire size do I need to go 100 feet for a 60 amp service to a workshop?
#4 AWG copper is rated 60 amps at 60°C and 70 amps at 75°C. #2 AWG aluminum is rated 60 amps at 60°C and 75 amps at 75°C. If your breaker and panel accept 75°C terminations, you’re good at 60 amps. For long runs, add about 3% voltage drop to your calculation. Use THHN/THWN-2 conductors in conduit for protection and longevity.
What size wire do I need to run a 100 amp service 200 feet?
At 200 feet, voltage drop becomes the real concern. 1 AWG copper drops about 3.2% at full load; 2/0 AWG aluminum drops roughly 3.0%. Both meet NEC’s 3% recommendation for branch circuits. Use 75°C-rated wire unless equipment labels say otherwise. For outdoor runs, go with XHHW-2 or USE-2 conductors rated for wet locations.
Can you run 220 on 100 amps?
Yes—you can run 220V/240V circuits on a 100 amp panel without issue.
A 100 amp panel handles 240V circuits just fine. The total load must stay under 100 amps after applying NEC 220.82 or 220.83 demand factors. Use two-pole breakers sized for the load, and keep neutral and ground separate in subpanels. Common uses include welders, compressors, and EV chargers—just double-check the equipment’s ampacity and wire size.
Can you use a 100 amp breaker for a 125 amp sub panel?
No—you cannot protect a 125 amp subpanel with a 100 amp breaker unless the subpanel is listed for main breaker protection.
A 125 amp subpanel needs a 125 amp main breaker or main lugs with an upstream overcurrent device rated ≥125 amps. If you slap a 100 amp breaker on a 125 amp subpanel, the bus is unprotected above 100 amps. The only safe way is to use main lugs and protect the feeder with a 125 amp upstream breaker, or pick a subpanel with a main breaker slot and install a 125 amp breaker.
How many circuits can be on a 100 amp panel?
A typical 100 amp panel can hold 20 circuits, but the actual number depends on panel design and breaker types.
Standard 100 amp panels are often 20/24 or 20/30 space, meaning 20 full-size breakers plus 4–10 twin breakers (dual-pole) for a total of 24–30 circuits. Some compact panels squeeze in 42 circuits using half-size breakers. Always check the panel’s directory for maximum circuit counts and space limitations. Don’t exceed the panel’s listed rating or the busbar’s ampacity.
What size breaker do I need for a 100 amp sub panel?
The breaker feeding a 100 amp subpanel should be sized to protect the feeder conductors, typically 100 amps.
Use a two-pole 100 amp breaker in the main panel to protect the feeder. Size the feeder conductors to 100 amps using the 75°C column (#3 AWG copper or #1 AWG aluminum). If the subpanel is main lugs only, install main lugs and protect the feeder with a 100 amp breaker upstream. Always do a load calculation to confirm the actual load won’t exceed the feeder or panel rating.
Will 1 0 aluminum wire fit in a 100 amp breaker?
1/0 AWG aluminum is good for 125 amps in the 75°C column, which is over the breaker rating. You can use it on a 125 amp breaker, but not 100 amps. If you’re stuck with 1/0 aluminum, install a 125 amp breaker and confirm the panel accepts 125 amp feeders. For 100 amps, use #1 AWG aluminum (110 amps at 60°C, 130 amps at 75°C) and protect it with a 100 amp breaker.
What is a 2 pole 100 amp breaker?
A 2-pole 100 amp breaker is a double-pole circuit breaker that provides 240V protection at 100 amps for two hot wires.
It fits into two slots in a load center and protects multi-wire branch circuits or 240V appliances like welders, dryers, and subpanels. Examples include Square D Homeline HOM2100CP or Eaton BR2100. These breakers come in different trip curves (B, C, D) and are compatible with specific panel lines. Always match the breaker type and amperage to the panel brand and model.
How many amps will 2 gauge wire handle?
2 AWG copper wire handles 95 amps at 60°C and 115 amps at 75°C per NEC Table 310.15(B)(16).
| Wire Size | 60°C (A) | 75°C (A) |
|---|
| 2 AWG Copper | 95 | 115 |
| 1 AWG Copper | 110 | 130 |
| 1/0 AWG Aluminum | 100 | 120 |
Use the 75°C column unless your equipment terminals are only rated 60°C. For long runs or high ambient temperatures, consider upsizing to reduce voltage drop and heat. Always check the breaker and panel terminal ratings before finalizing wire size.
Edited and fact-checked by the FixAnswer editorial team.
