What wire size for 30 amps?

#10 AWG copper for short runs. For longer runs, check voltage drop — may need #8 or #6 AWG.

Copper vs aluminum wire?

Aluminum needs to be 2 sizes larger than copper for the same ampacity. Copper is more conductive per volume.

Two criteria determine wire size: ampacity (must carry the current) and voltage drop (must not exceed limit over length).

The calculator picks the larger wire. A = I × 2 × ρ × L / (V × drop%) for single-phase.

Check ampacity and voltage drop, use larger wire.

#10 AWG copper minimum. Check V-drop for long runs.

Aluminum needs 2 sizes larger for same ampacity.