Electrical Panel Load Calculator

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Electrical Panel Load Calculator

Calculate total connected load, demand load (after demand factors), and verify your electrical panel capacity per NEC guidelines.

### Panel Settings

Panel Voltage (V)

120V (Single Phase) 240V (Single Phase) 208V (Three Phase) 480V (Three Phase)

Phase

Single Phase Three Phase

Main Breaker Size (A)

### Lighting & Receptacle Loads

Floor Area (sq ft)

Occupancy Type

Residential (3 VA/sq ft) Office (3.5 VA/sq ft) Warehouse (2 VA/sq ft) Retail (5 VA/sq ft) School (2 VA/sq ft)

Small Appliance Circuits (qty)

Laundry Circuits (qty)

### Fixed Appliance Loads

Range / Oven (W)

Clothes Dryer (W)

Water Heater (W)

Dishwasher (W)

Garbage Disposal (W)

Other Fixed Appliances (W)

### HVAC Loads

Air Conditioning (W)

Electric Heat (W)

Largest Motor (W) — for 125% rule

Calculate Panel Load Results will appear here.

function eleCalc() { // --- Read inputs --- const voltage = parseFloat(document.getElementById('ele-voltage').value); const phase = parseInt(document.getElementById('ele-phase').value); const breaker = parseFloat(document.getElementById('ele-breaker').value); const sqft = parseFloat(document.getElementById('ele-sqft').value); const vaPerSqft = parseFloat(document.getElementById('ele-lighting-type').value); const saCircuits= parseFloat(document.getElementById('ele-small-appliance').value); const laundry = parseFloat(document.getElementById('ele-laundry').value); const rangeW = parseFloat(document.getElementById('ele-range').value); const dryerW = parseFloat(document.getElementById('ele-dryer').value); const whW = parseFloat(document.getElementById('ele-water-heater').value); const dwW = parseFloat(document.getElementById('ele-dishwasher').value); const dispW = parseFloat(document.getElementById('ele-disposal').value); const otherW = parseFloat(document.getElementById('ele-other-fixed').value); const acW = parseFloat(document.getElementById('ele-ac').value); const heatW = parseFloat(document.getElementById('ele-heat').value); const motorW = parseFloat(document.getElementById('ele-motor').value);

const resultDiv = document.getElementById('ele-result');

// --- Validation --- const fields = [voltage, phase, breaker, sqft, vaPerSqft, saCircuits, laundry, rangeW, dryerW, whW, dwW, dispW, otherW, acW, heatW, motorW]; if (fields.some(v => isNaN(v) || v ⚠ Please enter valid non-negative numbers in all fields.'; return; } if (breaker ⚠ Main breaker must be at least 15A.'; return; } if (sqft ⚠ Floor area must be greater than 0.'; return; } const saCircuitsActual = Math.max(2, saCircuits); // NEC requires minimum 2 const laundryActual = Math.max(1, laundry); // NEC requires minimum 1

// ============================================================ // NEC STANDARD METHOD (NEC 220.82 / 220.83 simplified) // ============================================================

// 1. General Lighting Load (NEC 220.12) const generalLighting = sqft * vaPerSqft;

// 2. Small Appliance & Laundry Circuits (NEC 220.52) // Each circuit = 1500 VA const smallApplianceLoad = saCircuitsActual * 1500; const laundryLoad = laundryActual * 1500;

// 3. Subtotal before lighting demand factor const lightingSubtotal = generalLighting + smallApplianceLoad + laundryLoad;

// 4. Apply NEC Lighting Demand Factor (NEC Table 220.42 — Residential) // First 3000 VA @ 100%, next 3001–120000 VA @ 35%, remainder @ 25% let lightingDemand = 0; if (lightingSubtotal 12kW add 5% per kW over 12) let rangeDemand = 0; if (rangeW > 0) { if (rangeW 0 ? Math.max(5000, dryerW) : 0;

// 7. Fixed Appliances Demand (NEC 220.53) // If 4 or more fixed appliances (excl. range, dryer, A/C, heat): apply 75% demand factor const fixedAppliances = [whW, dwW, dispW, otherW].filter(v => v > 0); const fixedCount = fixedAppliances.length; const fixedTotal = fixedAppliances.reduce((a, b) => a + b, 0); const fixedDemandFactor = fixedCount >= 4 ? 0.75 : 1.0; const fixedDemand = fixedTotal * fixedDemandFactor;

// 8. HVAC — Use larger of A/C or Heat (NEC 220.60 — non-coincident loads) // A/C @ 100%, Heat @ 100% (electric resistance), take the larger const hvacDemand = Math.max(acW, heatW);

// 9. Largest Motor 125% adder (NEC 430.24) const motorAdder = motorW * 0.25; // 25% added on top of the motor's full load

// ============================================================ // TOTALS // ============================================================ const totalConnectedVA = generalLighting + smallApplianceLoad + laundryLoad + rangeW + dryerW + whW + dwW + dispW + otherW + acW + heatW + motorW;

const totalDemandVA = lightingDemand + rangeDemand + dryerDemand + fixedDemand + hvacDemand + motorW + motorAdder;

// Panel capacity (VA) = Voltage × Amperage (single phase) or V × A × √3 (three phase)
const sqrt3 = 1.7320508;
const panelCapacityVA = phase === 3
? voltage * breaker * sqrt3: voltage * breaker;
// Demand current
const demandCurrentA = phase === 3
? totalDemandVA / (voltage * sqrt3): totalDemandVA / voltage;

// Load percentage const loadPct = (demandCurrentA / breaker) * 100;

// NEC 80% continuous load rule
const continuousLimit = breaker * 0.80;
const continuousLimitVA = phase === 3
? continuousLimit * voltage * sqrt3: continuousLimit * voltage;

// Status let status, statusColor; if (loadPct s >= minBreakerNeeded) || '> 2000';

// Spare capacity const spareVA = Math.max(0, continuousLimitVA - totalDemandVA); const spareAmps = Math.max(0, continuousLimit - demandCurrentA);

resultDiv.innerHTML = ` ### Panel Load Analysis Results

ParameterValue General Lighting Load\${generalLighting.toLocaleString()} VA Small Appliance Circuits (\${saCircuitsActual} × 1500 VA)\${smallApplianceLoad.toLocaleString()} VA Laundry Circuits (\${laundryActual} × 1500 VA)\${laundryLoad.toLocaleString()} VA Lighting Subtotal (before demand factor)\${lightingSubtotal.toLocaleString()} VA Lighting Demand (after NEC Table 220.42)\${lightingDemand.toFixed(0).replace(/\B(?=(\d{3})+(?!\d))/g,',')} VA Range Demand (NEC Table 220.55)\${rangeDemand.toFixed(0).replace(/\B(?=(\d{3})+(?!\d))/g,',')} VA Dryer Demand (NEC 220.54)\${dryerDemand.toLocaleString()} VA Fixed Appliances (\${fixedCount} units × \${(fixedDemandFactor*100).toFixed(0)}% demand)\${fixedDemand.toFixed(0).replace(/\B(?=(\d{3})+(?!\d))/g,',')} VA HVAC Demand (larger of A/C or Heat)\${hvacDemand.toLocaleString()} VA Motor Load + 25% Adder\${(motorW + motorAdder).toFixed(0)} VA Total Connected Load\${totalConnectedVA.toLocaleString()} VA (\${(totalConnectedVA/1000).toFixed(2)} kVA) Total Demand Load (NEC)\${totalDemandVA.toFixed(0).replace(/\B(?=(\d{3})+(?!\d))/g,',')} VA (\${(totalDemandVA/1000).toFixed(2)} kVA) Demand Current\${demandCurrentA.toFixed(1)} A Panel Capacity (\${voltage}V, \${phase}Ø, \${breaker}A)\${panelCapacityVA.toLocaleString()} VA (\${(panelCapacityVA/1000).toFixed(2)} kVA) NEC 80% Continuous Limit\${continuousLimit.toFixed(1)} A / \${continuousLimitVA.toFixed(0).replace(/\B(?=(\d{3})+(?!\d))/g,',')} VA Panel Load Percentage\${loadPct.toFixed(1)}% Spare Capacity (at 80% rule)\${spareAmps.toFixed(1)} A / \${spareVA.toFixed(0).replace(/\B(?=(\d{3})+(?!\d))/g,',')} VA Minimum Recommended Breaker\${recommendedBreaker} A

\${status}

`; }

#### Formulas Used (NEC Standard Method)

1. General Lighting Load (NEC 220.12): Lighting VA = Floor Area (sq ft) × VA/sq ft factor

2. Small Appliance & Laundry (NEC 220.52): Each circuit = 1,500 VA (minimum 2 small appliance + 1 laundry required)

3. Lighting Demand Factor (NEC Table 220.42): First 3,000 VA @ 100% + Next (3,001–120,000 VA) @ 35% + Remainder @ 25%

4. Range Demand (NEC Table 220.55): Single unit ≤ 12 kW → 8,000 VA; >12 kW → 8,000 + 5% per kW over 12 kW

5. Dryer Demand (NEC 220.54): max(5,000 W, nameplate rating) @ 100%

6. Fixed Appliance Demand (NEC 220.53): < 4 appliances → 100%; ≥ 4 appliances → 75% demand factor

7. HVAC — Non-Coincident Loads (NEC 220.60): Use the larger of A/C or Electric Heat (they don't run simultaneously)

8. Largest Motor 125% Rule (NEC 430.24): Motor VA × 1.25 (25% adder on largest motor)

9. Panel Capacity: Single Phase: VA = V × A Three Phase: VA = V × A × √3

10. Demand Current: Single Phase: I = Total Demand VA ÷ V Three Phase: I = Total Demand VA ÷ (V × √3)

11. NEC 80% Continuous Load Rule (NEC 210.20, 215.3): Continuous loads must not exceed 80% of breaker rating. Load % = (Demand Current ÷ Breaker Rating) × 100

#### Assumptions & References

Calculations follow NEC 2023 (NFPA 70) Standard Method for dwelling units.
Lighting demand factors from NEC Table 220.42 (residential occupancy = 3 VA/sq ft per NEC 220.12).
Small appliance circuits: minimum 2 required per NEC 220.52(A); laundry minimum 1 per NEC 220.52(B).
Range demand based on NEC Table 220.55, Column C (single household cooking appliance).
Dryer demand per NEC 220.54: 5,000 W minimum or nameplate, whichever is greater.
Fixed appliance 75% demand factor applies when 4 or more appliances per NEC 220.53.
Non-coincident HVAC loads: only the larger of A/C or heat is counted per NEC 220.60.
Motor 125% rule per NEC 430.24 applies to the largest motor only.
NEC 80% rule for continuous loads per NEC 210.20(A) and 215.3.
Standard breaker sizes per NEC 240.6(A).

Electrical Panel Load Calculator

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