Electrical Load Calculation

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Electrical Load Calculator

General Living Area
Large Appliances (Watts)
General Lighting Load (3VA/sqft): 0 VA
Small Appliance/Laundry Load: 0 VA
Total Demand Load (After NEC Factors): 0 VA
Fixed Equipment Load: 0 VA
Recommended Service: 0 Amps

*Calculated based on 240V single-phase residential service using standard NEC demand factors.

Understanding Residential Electrical Load Calculation

Calculating the electrical load for a home is a critical step for homeowners, electricians, and DIYers alike. Whether you are upgrading an old service panel, adding a sub-panel, or installing an electric vehicle (EV) charger, you need to ensure your service entrance can handle the total Volt-Amps (VA) required by your appliances and lighting.

The NEC Standard Calculation Method

The National Electrical Code (NEC) provides specific guidelines for determining the minimum service size. This calculator uses the standard calculation method (Article 220) which applies demand factors to lighting and appliance loads because not every light and appliance in your house will be turned on at the exact same time.

  • General Lighting: Calculated at 3 Volt-Amps (VA) per square foot of living space.
  • Small Appliance Circuits: Each kitchen and laundry circuit is rated at 1,500 VA.
  • Demand Factors: The first 3,000 VA of general load is calculated at 100%. The remaining amount (up to 120,000 VA) is calculated at 35%.
  • Large Appliances: Specific loads like dryers, ranges, and HVAC units are added based on their nameplate ratings or specific NEC demand tables.

Common Appliance Wattage Examples

When using the calculator, it helps to have realistic estimates for your appliances. If you cannot find the nameplate on your device, here are common industry averages:

  • Electric Range: 8,000W to 12,000W
  • Electric Clothes Dryer: 5,000W
  • Electric Water Heater: 4,500W
  • Central Air Conditioning (3-ton): 5,000W
  • Level 2 EV Charger: 7,600W to 11,500W
  • Dishwasher: 1,200W

How to Choose the Right Panel Size

Once you determine the calculated amperage, you must choose a standard service size. Common residential service sizes are 100 Amps, 150 Amps, 200 Amps, and 400 Amps. If your calculation results in 165 Amps, you should install a 200-Amp service to provide "headroom" for future expansion and to comply with local codes.

Safety Disclaimer

This electrical load calculator is for estimation and educational purposes only. Electrical installations should always be performed by a licensed professional electrician in accordance with local building codes and the National Electrical Code. Overloading an electrical panel can lead to fire hazards and equipment failure.

function calculateLoad() { // Inputs var sqft = parseFloat(document.getElementById('elc_sqft').value) || 0; var kitchenCount = parseFloat(document.getElementById('elc_kitchen').value) || 0; var laundryCount = parseFloat(document.getElementById('elc_laundry').value) || 0; var range = parseFloat(document.getElementById('elc_range').value) || 0; var dryer = parseFloat(document.getElementById('elc_dryer').value) || 0; var water = parseFloat(document.getElementById('elc_water').value) || 0; var hvac = parseFloat(document.getElementById('elc_hvac').value) || 0; var misc = parseFloat(document.getElementById('elc_dishwasher').value) || 0; var ev = parseFloat(document.getElementById('elc_ev').value) || 0; // 1. General Lighting & Receptacle Load (3VA per sqft) var lightingVA = sqft * 3; // 2. Small Appliance & Laundry Circuits (1500VA each) var circuitVA = (kitchenCount * 1500) + (laundryCount * 1500); // 3. Apply Demand Factors for General Load var totalGeneral = lightingVA + circuitVA; var demandGeneral = 0; if (totalGeneral <= 3000) { demandGeneral = totalGeneral; } else { demandGeneral = 3000 + ((totalGeneral – 3000) * 0.35); } // 4. Fixed Loads // Note: Standard method often takes Range/Dryer with demand factors, // but for a simplified conservative calculator we add full load or 100% for these fixed items. var fixedEquipment = range + dryer + water + hvac + misc + ev; // 5. Final Calculation var totalVA = demandGeneral + fixedEquipment; var totalAmps = totalVA / 240; // Update UI document.getElementById('res_lighting').innerText = lightingVA.toLocaleString() + " VA"; document.getElementById('res_circuits').innerText = circuitVA.toLocaleString() + " VA"; document.getElementById('res_demand').innerText = Math.round(demandGeneral).toLocaleString() + " VA"; document.getElementById('res_fixed').innerText = fixedEquipment.toLocaleString() + " VA"; var ampDisplay = Math.ceil(totalAmps); var panelRecommendation = ""; if (ampDisplay <= 100) panelRecommendation = "100 Amp Service"; else if (ampDisplay <= 125) panelRecommendation = "125 Amp Service"; else if (ampDisplay <= 150) panelRecommendation = "150 Amp Service"; else if (ampDisplay <= 200) panelRecommendation = "200 Amp Service"; else if (ampDisplay <= 400) panelRecommendation = "400 Amp Service"; else panelRecommendation = "Commercial/High Capacity Service Required"; document.getElementById('res_amps').innerText = ampDisplay + " Amps (" + panelRecommendation + ")"; document.getElementById('elc_result').style.display = 'block'; }

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