600 kcmil vs 700 kcmil Copper
Going from 600 kcmil to 700 kcmil adds 40A of capacity and extends maximum wire run distance before hitting the 3% voltage drop limit. The trade-off is cost: 700 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 | 600 kcmil | 700 kcmil |
|---|---|---|
| 90°C ampacity | 475A | 520A |
| Usable ampacity | 420A | 460A |
| Standard breaker | 200A | 200A |
| Conduit (EMT) | 2" EMT | 2" EMT |
Voltage drop crossover
At what distance does 600 kcmil fail the 3% recommendation and 700 kcmil still passes? This shows the distance where upsizing is required, not optional.
Load: 420A on 240V single-phase.
| Distance | Verdict | 600 kcmil | 700 kcmil |
|---|---|---|---|
| 25 ft | Either works | 0.2% | 0.0% |
| 50 ft | Either works | 0.4% | 0.0% |
| 75 ft | Either works | 0.6% | 0.0% |
| 100 ft | Either works | 0.8% | 0.0% |
| 125 ft | Either works | 0.9% | 0.0% |
| 150 ft | Either works | 1.1% | 0.0% |
| 200 ft | Either works | 1.5% | 0.0% |
| 250 ft | Either works | 1.9% | 0.0% |
| 300 ft | Either works | 2.2% | 0.0% |
When to upsize
Stay with 600 kcmil when
- Circuit load is within 420A capacity
- Wire run is short (under ~405 ft at 240V)
- Budget is the primary constraint
Upsize to 700 kcmil when
- You need more than 420A (loads up to 460A)
- Wire run is long and voltage drop is a concern
- Future load growth is expected on this circuit
Detailed ampacity: 600 kcmil copper, 700 kcmil copper. Material comparison: 600 kcmil Cu vs Al, 700 kcmil Cu vs Al.
Frequently asked questions
Can I use 600 kcmil instead of 700 kcmil?
Only if your load is 420A or less and your wire run is short enough to stay within 3% voltage drop. 600 kcmil carries 420A maximum. If you need more than 420A, or your run exceeds the distance limit, you must use 700 kcmil or larger.
How much more does 700 kcmil cost than 600 kcmil?
700 kcmil typically costs 40-60% more per foot than 600 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 600 kcmil: buy NM-B cable for in-wall residential or individual THHN conductors for conduit. For 700 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 700 kcmil Copper circuits
As an Amazon Associate we earn from qualifying purchases.
NEC 2023 references verified February 2026