Electrical Load Calculator
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Size circuit breaker from wire gauge and load type. Match overcurrent protection to conductor ampacity per NEC 240.4 for residential circuits.
Select AWG wire size from ampacity and circuit load. Calculate conductor size for copper and aluminum per NEC ampacity tables with temperature rating.
Calculate voltage drop on wire runs for NEC compliance. Enter wire size, length, amperage, and voltage to find drop percent and minimum wire size.
Sum nameplate wattages for all fixed appliances, HVAC, and general lighting/receptacle loads.
Connected Load (W) = Σ All Circuit and Appliance WattsNEC Table 220 applies demand factors — not all loads run simultaneously. First 10 kW general load at 100%, remainder at 40%.
Demand = Connected × Demand Factor (varies by load type)Divide total demand watts by system voltage for required service ampacity before conductor sizing.
Amps = Demand Watts ÷ (Voltage × PF); Single phase 240V: W ÷ 240Updated: July 2026
General load 18 kW with demand factors, plus AC, range, dryer → ~24 kW demand. 100A service may be inadequate — 200A typical.
Heat pump adds significant demand. Apply NEC heating demand factors — larger of heat or AC, not both at 100%.
Calculate subpanel load separately. Main service must support main demand plus subpanel after applicable factors.
Estimate total residential electrical demand for service panel sizing and load analysis. Enter appliance and circuit wattages with NEC-style demand factors to calculate connected load, adjusted demand, and required service amperage.