Wire Voltage-Drop Calculator for ASIC Miner Circuits & Solar DC Runs
Quick answer
Voltage drop on a single-phase or 2-wire DC run is Vdrop = 2 × I × R × L ÷ 1000, where I is the load current (A), L the one-way run length (ft), and R the conductor’s DC resistance in ohms per 1,000 ft. Example: a 24 A load on a 150 ft run of 10 AWG copper at 240 V drops about 8.7 V (3.6%) — over the NEC’s recommended 3% branch-circuit limit, so stepping up to 8 AWG brings it down to 5.5 V (2.3%). The 3% (branch) and 5% (branch + feeder combined) figures are NEC informational-note recommendations for efficiency, not code requirements — but a big drop is a real cause of ASIC PSU under-voltage brownout-resets on long garage/shed feeders.
Rule of thumb: keep branch-circuit voltage drop at or under 3%. If a run pushes past that, go one conductor size larger (or shorten the run) — this tool tells you the smallest gauge that gets you there.
Method. This computes voltage drop for a single-phase AC or two-wire DC circuit: the current travels out on one conductor and back on the other, so the total resistance in the loop is twice the one-way length — hence Vdrop = 2 × I × R × L ÷ 1000. Conductor DC resistance R (ohms per 1,000 ft, 75 °C) comes straight from D-Central’s conductor reference (NEC Chapter 9 Table 8). It ignores AC reactance, which is negligible for the short, low-inductance feeders and near-unity-power-factor ASIC loads this serves, so results are slightly conservative. For three-phase circuits the formula differs (use √3 line-to-line, not the 2× here). The 3%/5% targets are NEC 210.19(A)/215.2(A) informational-note recommendations, not mandatory limits. Estimates only, not a stamped design — have a licensed electrician verify and follow local code (the CEC in Canada). Related: the home-mining circuit planner (breaker & continuous-load sizing) and the wire-sizing ampacity reference.
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Last reviewed July 21, 2026.