Electrical Panel Load Balancing Calculator
Calculate load distribution across electrical panel phases, identify imbalances, and optimize circuit assignments for single-phase and three-phase panels.
Circuit Loads
Enter each circuit's amperage and assign it to a phase. Add up to 20 circuits.
Circuit 1
Circuit 2
Circuit 3
Circuit 4
Formulas Used
Phase Power (W): Pphase = VL-N × Iphase
Total Load: Ptotal = PA + PB + PC
Average Phase Load: Iavg = (IA + IB [+ IC]) / Nphases
Load Imbalance % (Three-Phase, NEMA MG-1):
% Imbalance = (max|Iphase − Iavg| / Iavg) × 100
Load Imbalance % (Single-Phase):
% Imbalance = (|IA − IB| / Iavg) × 100
Panel Utilization %: (Ptotal / Pcapacity) × 100
NEC 80% Continuous Load Rule: Icontinuous ≤ 0.8 × Ibreaker
Assumptions & References
- Loads are treated as purely resistive (unity power factor) for current-based calculations.
- Line-to-neutral voltage is used for per-phase power: 120V (residential), 120V (208V 3-phase), 277V (480V 3-phase).
- NEC Article 220 and 80% continuous load rule per NEC 210.20(A) and 215.2(A)(1).
- Three-phase imbalance threshold follows NEMA MG-1 (≤5% recommended, >10% causes motor derating).
- Single-phase imbalance is calculated as the deviation between Phase A and Phase B relative to their average.
- Panel capacity is calculated as: main breaker (A) × line-to-neutral voltage × number of phases.
- Neutral current for three-phase systems is not calculated (assumes balanced or near-balanced loads).
- This calculator does not account for demand factors, diversity factors, or motor starting currents.
- References: NEC 2023 (NFPA 70), NEMA MG-1, IEEE Std 1159, ANSI C84.1.