Solar & battery
Solar Cable Size Calculator
DC cable size for a solar run, sized on voltage drop rather than ampacity alone.
Result
DC circuits are held to a tighter drop than AC because the voltage is lower, so the same lost volts are a much larger share. This sizes on voltage drop only; the cable must independently satisfy ampacity, conduit fill, temperature derating and any code requirement for the specific conductor type. Solar DC circuits also have their own NEC article with additional rules.
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About this calculator
Why 2% rather than 3%?
Because a 48 V system losing 3% loses 1.4 volts, which matters at charging voltages. Low-voltage DC is far less tolerant of drop than 240 V AC.
Does array wiring configuration matter?
Considerably. Wiring panels in series raises voltage and cuts current for the same power, which shrinks the cable needed dramatically over a long run.
The formula
circular mils = 2 x K x amps x distance / allowable volts dropped
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