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Electrical Load Calculator (Amps)

Quick answer

Add up appliance wattages to size your service: total W, load current I = P/(V x PF), panel size at 125 percent continuous, with breaker and cable hints.

Figures are estimates from this calculator’s standard formula — adjust the inputs in the tool below for your exact number.

How the Electrical Load Calculator Works

Total Current = Total Power / (Voltage × Power Factor)

Sums all electrical loads to determine total power demand, then calculates the current draw to recommend appropriate panel and cable sizes for safe installation. Worked example: loads totaling 7200 W on 230 V single-phase draw I = 7200/230 = 31.3 A; NEC 220 requires sizing the feeder at 125 percent for continuous loads, giving 39.1 A - a 40 A breaker and 8 AWG copper. Demand factors matter: an all-electric kitchen measuring 18 kW connected rarely exceeds 9 kW simultaneous, and NEC 220 allowances for ranges and dryers let the service stay smaller than the raw sum.

  1. 1

    Step 1

    Enter system voltage and power factor

  2. 2

    Step 2

    Add each electrical load with its power and quantity

  3. 3

    Step 3

    View total power and current demand

  4. 4

    Step 4

    Get recommended panel and cable sizes

Use Cases

Designing residential electrical panels

Planning commercial building power distribution

Sizing main breakers and service entrance

Estimating power requirements for renovations

Tips

  • 1

    Include 25% safety margin for future expansion

  • 2

    Diversity factor reduces total for unlikely simultaneous use

  • 3

    Continuous loads require 125% breaker sizing

  • 4

    NEC requires specific sizing for different load types

Common Mistakes

  • Adding loads without diversity factor (over-sizing)

  • Forgetting future load growth allowance

  • Not classifying continuous vs intermittent loads

  • Ignoring power factor in industrial calculations

FAQs

What is diversity factor?

Diversity factor accounts for loads not running simultaneously. A home might have 30kW of loads but only 15kW peak demand. Diversity = Peak / Total, typically 0.4-0.8.

How do I size the main breaker?

Calculate total demand with diversity factor, add 25% for continuous loads, then select next standard breaker size up. Always follow local electrical codes.

What cable size do I need?

Cable size depends on current, distance, and installation method. Use ampacity tables from NEC/IEC, derate for temperature and bundling, and check voltage drop.

How do I calculate total electrical load?

List every appliance's watts, multiply non coincident loads by demand factors (NEC 220.83 allows 100 percent of first 8 kVA plus 40 percent of remainder for dwellings), then sum. Divide by voltage for amps.

What size breaker do I need?

Breaker rating at 125 percent of continuous load (NEC 210.20(A)). A 16 A continuous load needs a 20 A breaker; the conductor must match: 12 AWG copper for 20 A circuits per NEC 310.15.

How do I size a main panel?

Sum computed loads, add 25 percent headroom, pick the next standard size. Typical homes: 100-200 A. A 9 kW total at 230 V is 39 A minimum, so a 100 A panel gives ample spare capacity.

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