Code reference · NEC Table 310.16; Ch.9 Table 8; 210.19(A) IN; 110.14(C)
Wire size for 30 amps at 150 feet (240 V)
30 A at 150 ft one-way on a 240 V circuit: the engine-computed answer is 8 AWG copper (or 4 AWG aluminum). That size carries the load under Table 310.16 with standard derates and lands at 2.87% voltage drop — inside the NEC's recommended 3% for a branch circuit (210.19(A) Informational Note).
Ampacity alone would let you use 10 AWG (good for 35 A derated), but at 150 ft that conductor drops 10.89 V (4.54%) — past the 3% guideline. Distance, not ampacity, sets the size here; run length is why "what wire for 30 amps" has no one answer.
Notes that survive inspection: the 3%/5% figures are Informational Notes — recommended, not enforceable, in most jurisdictions (some local amendments make them binding); a continuous load (3+ hours) needs conductors and OCPD at 125% of the load (210.19(A)/210.20(A)); and these numbers assume ≤3 current-carrying conductors at 30°C — attics and bundled raceways derate further (310.15).
Run the numbers yourself
Need this as a permit-ready document?
One Document Credit ($29) buys a full clause-cited compliance PDF — wire sizing, voltage drop, overcurrent protection, every value traceable to the section it came from.
Get your document →Every numeric value on this page is computed by the CircuitProof calculation engine — the same golden-tested code that renders our permit documents — not typed by hand. Code text is paraphrased and cited; always verify against your jurisdiction's adopted edition and a licensed professional before installation. Design documentation, not a stamped drawing.
More references: Wire size for 20 amps at 100 feet (240 V) · Wire size for 30 amps at 100 feet (240 V) · Wire size for 40 amps at 100 feet (240 V) · Wire size for 50 amps at 50 feet (240 V) · Wire size for 50 amps at 100 feet (240 V) · Wire size for 50 amps at 150 feet (240 V) · all 97 references