Branch Voltage Drop With Multiple Loads
Cumulative voltage at each tap along a run with multiple loads.
Example
You enter
- Conductor material copper
- AWG 12
- Source voltage (V) 120
- Loads distance (ft) 50, current (A) 5; distance (ft) 100, current (A) 10
You get
- Worst-case drop 4.94 V
- Worst voltage at load 115.06 V
- Worst percent 4.12 %
Checked against published worked examples from: EC&M (Mike Holt, author).
Details, formula, and sources
Formula or tableCumulative I × R per ordered segment; single-phase round-trip; allows mixed loads along one circuit.
Source and editionNEC 2023 (NFPA 70). Chapter 9 Tables 8 / 9; IEEE 141 by name.
Free accessFree read-only access at nfpa.org/freeaccess.
What governsEstimate. AHJ and licensed electrician govern. Verify against the NEC edition adopted in your jurisdiction.
API field namesmaterial, awg, source_voltage_V, loads, worst_drop_V, worst_voltage_V, worst_percent
- Round-trip factor 2× one-way lengthsingle-phase return path