Outdoor Lighting Circuit Load Calculator

ANA›Life Services Authority›National Calculator Authority›Outdoor Lighting Circuit Load Calculator

.calc-container { max-width: 640px; margin: 2rem 0; padding: 1.5rem; background: #fff; border: 1px solid #ddd; border-radius: 8px; box-shadow: 0 1px 3px rgba(0,0,0,0.06); font-family: system-ui, -apple-system, sans-serif; } .calc-container h3 { font-family: Georgia, serif; font-size: 1.15rem; color: #1a1a1a; margin-bottom: 1rem; padding-bottom: 0.5rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-row { display: flex; align-items: center; gap: 0.75rem; margin-bottom: 0.75rem; flex-wrap: wrap; } .calc-row label { min-width: 160px; font-size: 0.9rem; color: #333; font-weight: 500; } .calc-row input[type="number"], .calc-row select { flex: 1; min-width: 120px; max-width: 200px; padding: 0.5rem 0.6rem; border: 1px solid #ccc; border-radius: 4px; font-size: 0.9rem; font-family: system-ui, sans-serif; color: #1a1a1a; background: #fafaf8; } .calc-row input:focus, .calc-row select:focus { outline: none; border-color: var(--ac, #3d5a80); box-shadow: 0 0 0 2px rgba(26,74,138,0.12); } .calc-row .unit { font-size: 0.82rem; color: #888; min-width: 30px; } .calc-btn { display: inline-block; margin-top: 0.5rem; padding: 0.55rem 1.5rem; background: var(--ac, #3d5a80); color: #fff; border: none; border-radius: 4px; font-size: 0.9rem; font-weight: 600; cursor: pointer; font-family: system-ui, sans-serif; } .calc-btn:hover { opacity: 0.9; } .calc-result { margin-top: 1.25rem; padding: 1rem 1.25rem; background: #f0f6fc; border-left: 3px solid var(--ac, #3d5a80); border-radius: 0 6px 6px 0; display: none; } .calc-result.visible { display: block; } .calc-result-label { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.06em; color: #666; margin-bottom: 0.25rem; } .calc-result-value { font-size: 1.6rem; font-weight: 700; color: var(--ac, #3d5a80); } .calc-result-detail { font-size: 0.85rem; color: #555; margin-top: 0.5rem; line-height: 1.5; } .calc-note { margin-top: 1rem; font-size: 0.8rem; color: #888; font-style: italic; } .calc-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; margin-top: 0.75rem; } .calc-grid-item { padding: 0.6rem 0.8rem; background: #f8f9fa; border-radius: 4px; border: 1px solid #eee; } .calc-grid-item .label { font-size: 0.75rem; color: #888; text-transform: uppercase; letter-spacing: 0.04em; } .calc-grid-item .value { font-size: 1.1rem; font-weight: 600; color: #1a1a1a; } @media (max-width: 720px) { .calc-row { flex-direction: column; align-items: flex-start; gap: 0.3rem; } .calc-row label { min-width: auto; } .calc-row input[type="number"], .calc-row select { max-width: 100%; width: 100%; } .calc-grid { grid-template-columns: 1fr; } } .calc-chart { margin: 1rem 0; text-align: center; } .calc-chart svg { max-width: 100%; height: auto; } .calc-chart-legend { display: flex; flex-wrap: wrap; justify-content: center; gap: 0.6rem 1.2rem; margin-top: 0.6rem; font-size: 0.8rem; color: #555; } .calc-chart-legend span { display: inline-flex; align-items: center; gap: 0.3rem; } .calc-chart-legend i { display: inline-block; width: 10px; height: 10px; border-radius: 2px; font-style: normal; } .calc-related { max-width: 640px; margin: 2rem 0 1rem; padding: 1.25rem 1.5rem; background: #f8f9fa; border: 1px solid #e8e8e8; border-radius: 8px; } .calc-related h3 { font-family: Georgia, serif; font-size: 1rem; color: #1a1a1a; margin: 0 0 0.75rem; padding-bottom: 0.4rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-related-list { list-style: none; padding: 0; margin: 0 0 0.75rem; display: grid; grid-template-columns: 1fr 1fr; gap: 0.4rem 1.5rem; } .calc-related-list li a { font-size: 0.88rem; color: var(--ac, #3d5a80); text-decoration: none; } .calc-related-list li a:hover { text-decoration: underline; } .calc-browse-all { margin: 0.5rem 0 0; font-size: 0.9rem; font-weight: 600; } .calc-browse-all a { color: var(--ac, #3d5a80); text-decoration: none; } .calc-browse-all a:hover { text-decoration: underline; } @media (max-width: 720px) { .calc-related-list { grid-template-columns: 1fr; } }

Outdoor Lighting Circuit Load Calculator

Calculate total circuit load, current draw, and recommended breaker/wire sizing for outdoor lighting circuits per NEC guidelines.

Supply Voltage (V)

120V (Standard US) 240V 277V (Commercial) 12V (Low Voltage) 24V (Low Voltage)

Power Factor

1.00 – Resistive / LED (ideal) 0.95 – LED drivers (typical) 0.90 – Fluorescent 0.85 – HID / Metal Halide 0.80 – Older HID

Enter up to 6 fixture groups:

Fixture Type / Description

Watts per Fixture (W)

Quantity

Fixture Type / Description

Watts per Fixture (W)

Quantity

Fixture Type / Description

Watts per Fixture (W)

Quantity

Fixture Type / Description

Watts per Fixture (W)

Quantity

Fixture Type / Description

Watts per Fixture (W)

Quantity

Fixture Type / Description

Watts per Fixture (W)

Quantity

NEC Continuous Load Derating

125% – Continuous load (>3 hrs, NEC 210.20) 100% – Non-continuous load

System Phases

Single-Phase Three-Phase

Calculate

function outCalc() { var resultDiv = document.getElementById('out-result'); resultDiv.innerHTML = '';

var voltage = parseFloat(document.getElementById('out-voltage').value); var pf = parseFloat(document.getElementById('out-pf').value); var derating = parseFloat(document.getElementById('out-derating').value); var phases = parseInt(document.getElementById('out-phases').value);

// Collect fixture groups var groups = []; var totalWatts = 0; for (var i = 0; i 0 && q > 0) { var groupW = w * q; totalWatts += groupW; groups.push({ desc: dEl.value.trim() || ('Group ' + (i+1)), wPer: w, qty: q, total: groupW }); } }

// Validation if (groups.length === 0) { resultDiv.innerHTML = 'Please enter at least one fixture group (watts and quantity).

'; return; } if (isNaN(voltage) || voltage = currentDerated) { breakerSize = standardBreakers[b]; break; } } if (breakerSize === null) breakerSize = '>400A – consult engineer';

// Wire gauge recommendation (copper, 60°C, NEC 310.15 ampacity table, single-phase branch circuit) // Ampacity thresholds for common AWG sizes var wireTable = [ {awg:'14 AWG', amp:15}, {awg:'12 AWG', amp:20}, {awg:'10 AWG', amp:30}, {awg:'8 AWG', amp:40}, {awg:'6 AWG', amp:55}, {awg:'4 AWG', amp:70}, {awg:'3 AWG', amp:85}, {awg:'2 AWG', amp:95}, {awg:'1 AWG', amp:110}, {awg:'1/0 AWG',amp:125}, {awg:'2/0 AWG',amp:145}, {awg:'3/0 AWG',amp:165}, {awg:'4/0 AWG',amp:195}, {awg:'250 kcmil',amp:215}, {awg:'300 kcmil',amp:240}, {awg:'350 kcmil',amp:260}, {awg:'400 kcmil',amp:280}, {awg:'500 kcmil',amp:320} ]; var wireGauge = 'Consult engineer'; for (var w2 = 0; w2 = currentDerated) { wireGauge = wireTable[w2].awg + ' Cu (ampacity: ' + wireTable[w2].amp + 'A)'; break; } }

// Circuit load percentage (relative to breaker)
var loadPct = (typeof breakerSize === 'number')
? ((currentDerated / breakerSize) * 100).toFixed(1): 'N/A';
// Max additional load on selected breaker
var headroom = (typeof breakerSize === 'number')
? ((breakerSize - currentDerated) * voltage * pf).toFixed(1): 'N/A';

// ── Build Results ────────────────────────────────────────────── var rows = ''; for (var g = 0; g ' + groups[g].desc + '' + groups[g].wPer.toFixed(1) + ' W' + '' + groups[g].qty + '' + groups[g].total.toFixed(1) + ' W'; }

var phaseLabel = (phases === 3) ? 'Three-Phase (√3 × V)' : 'Single-Phase'; var deratingLabel = (derating === 1.25) ? '125% (Continuous, NEC 210.20)' : '100% (Non-continuous)';

resultDiv.innerHTML = '### Results ' + '' + '' + 'Fixture Group' + 'W/Fixture' + 'Qty' + 'Group Total' + '' + rows + '' +

'' + 'Total Connected Load' + '' + totalWatts.toFixed(1) + ' W' + 'Power Factor' + '' + pf.toFixed(2) + '' + 'Apparent Power (VA)' + '' + apparentPowerVA.toFixed(1) + ' VA' + 'System' + '' + phaseLabel + ' @ ' + voltage + 'V' + 'Raw Current Draw' + '' + currentRaw.toFixed(2) + ' A' + 'NEC Derating Factor' + '' + deratingLabel + '' + 'Derated Design Current' + '' + currentDerated.toFixed(2) + ' A' + 'Recommended Breaker Size' + '' + breakerSize + (typeof breakerSize === 'number' ? 'A' : '') + '' + 'Recommended Wire Gauge' + '' + wireGauge + '' + 'Circuit Load Utilization' + '' + loadPct + '%' + 'Remaining Headroom (W)' + '' + headroom + ' W' + ''; }

#### Formulas Used

Apparent Power: S (VA) = Ptotal (W) ÷ Power Factor

Single-Phase Current: I = S ÷ V

Three-Phase Current: I = S ÷ (√3 × V)

NEC Derated Current (NEC 210.20): Idesign = I × 1.25 (continuous loads > 3 hours)

Breaker Size: Next standard OCPD size ≥ Idesign (NEC 240.6)

Wire Gauge: Copper conductor ampacity ≥ Idesign per NEC Table 310.15(B)(16)

Headroom: (Breaker Rating − Idesign) × V × PF

#### Assumptions & References

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References

10 CFR § 434.401 — § 434.401 Electrical power and lighting systems.

Outdoor Lighting Circuit Load Calculator

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