Panel Loading and Phase Rebalance
Per-phase totals, percent imbalance, and a swap suggestion to minimize neutral current.
Example
You enter
- Circuits description Kitchen, amps 20, phase A, and 5 more
You get
- Totals A (A) 65
- Totals B (A) 22
- Totals C (A) 12
- Mean (A) 33
- Imbalance (%) 160.61
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
ScopeCompanion to voltage-imbalance.
Formula or tablePer-phase total = sum of single-leg circuits on phase. Imbalance % = (max - min) / mean × 100. Greedy swap suggestion: move heaviest single-leg circuit on the heaviest phase to the lightest phase if the projected imbalance is reduced.
Source and editionNEC 2023 (NFPA 70). §220 (load calculations) and §408.36 (panel rating). NEMA MG-1 by name for the imbalance / horsepower derate cited adjacent to the result.
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 namescircuits, totals_A_amps, totals_B_amps, totals_C_amps, mean_amps, imbalance_pct
- Phases A / B / C single-leg circuits only (multi-pole breakers must be aggregated by the user)engineering practice
- Swap threshold imbalance > 5% triggers a suggestion (an engineering-practice 5% rebalance trigger on the max-min spread; NEMA MG-1's 1% is a VOLTAGE-unbalance limit for motors, measured as maximum deviation from the average, not a load-current spread)engineering practice