500 kcmil vs 600 kcmil Copper
Going from 500 kcmil to 600 kcmil adds 40A of capacity and extends maximum wire run distance before hitting the 3% voltage drop limit. The trade-off is cost: 600 kcmil copper costs more per foot and fits in the same conduit (2" EMT).
Specification comparison
Side-by-side specifications per NEC 2023 for THHN copper conductors.
| Property | 500 kcmil | 600 kcmil |
|---|---|---|
| 90°C ampacity | 430A | 475A |
| Usable ampacity | 380A | 420A |
| Standard breaker | 200A | 200A |
| Conduit (EMT) | 2" EMT | 2" EMT |
Voltage drop crossover
At what distance does 500 kcmil fail the 3% recommendation and 600 kcmil still passes? This shows the distance where upsizing is required, not optional.
Load: 380A on 240V single-phase.
| Distance | Verdict | 500 kcmil | 600 kcmil |
|---|---|---|---|
| 25 ft | Either works | 0.2% | 0.2% |
| 50 ft | Either works | 0.4% | 0.3% |
| 75 ft | Either works | 0.6% | 0.5% |
| 100 ft | Either works | 0.8% | 0.7% |
| 125 ft | Either works | 1.0% | 0.8% |
| 150 ft | Either works | 1.2% | 1.0% |
| 200 ft | Either works | 1.6% | 1.4% |
| 250 ft | Either works | 2.0% | 1.7% |
| 300 ft | Either works | 2.5% | 2.0% |
When to upsize
Stay with 500 kcmil when
- Circuit load is within 380A capacity
- Wire run is short (under ~365 ft at 240V)
- Budget is the primary constraint
Upsize to 600 kcmil when
- You need more than 380A (loads up to 420A)
- Wire run is long and voltage drop is a concern
- Future load growth is expected on this circuit
Detailed ampacity: 500 kcmil copper, 600 kcmil copper. Material comparison: 500 kcmil Cu vs Al, 600 kcmil Cu vs Al.
Frequently asked questions
Can I use 500 kcmil instead of 600 kcmil?
Only if your load is 380A or less and your wire run is short enough to stay within 3% voltage drop. 500 kcmil carries 380A maximum. If you need more than 380A, or your run exceeds the distance limit, you must use 600 kcmil or larger.
How much more does 600 kcmil cost than 500 kcmil?
600 kcmil typically costs 40-60% more per foot than 500 kcmil for the same insulation type. The larger wire also requires larger conduit (2" EMT vs 2" EMT). However, the lower voltage drop can save energy on long runs.
What to buy
If you are buying wire for a new installation, consider your total project requirements. For 500 kcmil: buy NM-B cable for in-wall residential or individual THHN conductors for conduit. For 600 kcmil: same insulation types apply but expect approximately 40-60% higher cost per foot. When in doubt about which gauge, upsize: the cost of the wire is a small fraction of the total project cost (labor, conduit, breaker, permits), and upgrading later means repulling the entire run.
Common products for 600 kcmil Copper circuits
As an Amazon Associate we earn from qualifying purchases.
NEC 2023 references verified February 2026