Lighting Energy Cost Calculator
ANA›Life Services Authority›National Calculator Authority›Lighting Energy Cost 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; } }
Lighting Energy Cost Calculator
Calculate how much your lighting costs per day, month, and year based on wattage, daily usage, and your electricity rate.
Bulb Wattage (W)
Number of Bulbs
Hours Used Per Day (hrs/day)
Electricity Rate ($/kWh)
Calculate
function ligCalc() { var errEl = document.getElementById('lig-error'); var resultEl = document.getElementById('lig-result'); errEl.style.display = 'none'; resultEl.style.display = 'none'; errEl.innerHTML = ''; resultEl.innerHTML = '';
var wattage = parseFloat(document.getElementById('lig-wattage').value); var bulbs = parseFloat(document.getElementById('lig-bulbs').value); var hours = parseFloat(document.getElementById('lig-hours').value); var rate = parseFloat(document.getElementById('lig-rate').value);
// --- Validation --- var errors = []; if (isNaN(wattage) || wattage 24) errors.push('Hours per day cannot exceed 24.'); if (isNaN(rate) || rate 0) { errEl.innerHTML = errors.map(function(e){ return '⚠ ' + e + '
'; }).join(''); errEl.style.display = 'block'; return; }
// --- Core Formula --- // Total power (kW) = (wattage × bulbs) / 1000 // Daily energy (kWh) = total_power_kW × hours_per_day // Daily cost ($) = daily_energy × rate // Monthly cost ($) = daily_cost × 30.4375 (365.25 / 12 average days/month) // Annual cost ($) = daily_cost × 365.25
var totalPowerKW = (wattage * bulbs) / 1000; var dailyKWh = totalPowerKW * hours; var dailyCost = dailyKWh * rate; var monthlyCost = dailyCost * 30.4375; var annualCost = dailyCost * 365.25; var annualKWh = dailyKWh * 365.25;
// Equivalent incandescent comparison (LED ~75% less energy than incandescent) var incandescentW = wattage * 4; // rough equivalence: 1 LED W ≈ 4 incandescent W var incandescentAnnualCost = ((incandescentW * bulbs) / 1000) * hours * rate * 365.25; var savings = incandescentAnnualCost - annualCost;
function fmt(n, d) { return n.toLocaleString('en-US', {minimumFractionDigits: d, maximumFractionDigits: d}); }
resultEl.innerHTML = '### Results ' + '' + 'Total Power Draw' + '' + fmt(totalPowerKW * 1000, 1) + ' W (' + fmt(totalPowerKW, 4) + ' kW)' + 'Daily Energy Use' + '' + fmt(dailyKWh, 4) + ' kWh' + 'Daily Cost' + '$' + fmt(dailyCost, 4) + '' + 'Monthly Cost' + '$' + fmt(monthlyCost, 2) + '' + 'Annual Cost' + '$' + fmt(annualCost, 2) + '' + 'Annual Energy Use' + '' + fmt(annualKWh, 2) + ' kWh' + '' + (savings > 0 ? '' + '⚡ If these are LED bulbs, you could be saving approximately $' + fmt(savings, 2) + '/year compared to equivalent incandescent bulbs (' + fmt(incandescentW * bulbs, 0) + ' W total).
- '
- '');
resultEl.style.display = 'block'; }
#### Formulas Used
Total Power (kW) = (Wattage per Bulb × Number of Bulbs) ÷ 1,000
Daily Energy (kWh) = Total Power (kW) × Hours Used per Day
Daily Cost ($) = Daily Energy (kWh) × Electricity Rate ($/kWh)
Monthly Cost ($) = Daily Cost × 30.4375 (= 365.25 ÷ 12)
Annual Cost ($) = Daily Cost × 365.25
Annual Energy (kWh) = Daily Energy × 365.25
#### Assumptions & References
- The default electricity rate of $0.13/kWh is the approximate U.S. residential average (U.S. EIA, 2024).
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