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Roof Coating ROI and Energy Savings Calculator

ANA›Life Services Authority›National Calculator Authority›Roof Coating ROI and Energy Savings Calculator

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Roof Coating ROI and Energy Savings Calculator

Estimate your annual energy savings, payback period, and return on investment from applying a reflective roof coating to your building.

Roof Area (sq ft)

Coating Installation Cost ($/sq ft)

Electricity Rate ($/kWh)

Annual Cooling Energy Use (kWh/sq ft/year)

Cooling Load Reduction from Coating (%)

Expected Coating Lifespan (years)

Annual Roof Maintenance Savings ($/year) (optional)

Discount Rate / Inflation Rate (%) (for NPV)

Calculate ROI & Savings

function rooCalc() { var resultDiv = document.getElementById('roo-result');

var roofArea = parseFloat(document.getElementById('roo-roof-area').value); var coatingCost = parseFloat(document.getElementById('roo-coating-cost').value); var energyRate = parseFloat(document.getElementById('roo-energy-rate').value); var coolingLoad = parseFloat(document.getElementById('roo-cooling-load').value); var reductionPct = parseFloat(document.getElementById('roo-reduction-pct').value); var coatingLife = parseFloat(document.getElementById('roo-coating-life').value); var maintSavings = parseFloat(document.getElementById('roo-maintenance-savings').value) || 0; var discountRate = parseFloat(document.getElementById('roo-discount-rate').value);

// Validation var errors = []; if (isNaN(roofArea) || roofArea 60) errors.push("Cooling load reduction must be between 1% and 60%."); if (isNaN(coatingLife) || coatingLife 0) { resultDiv.innerHTML = ''; return; }

// ── Core Calculations ──────────────────────────────────────────────────────

// Total upfront investment // Total Cost = Roof Area (sq ft) × Cost per sq ft var totalInvestment = roofArea * coatingCost;

// Annual energy saved (kWh) // Energy Saved (kWh/yr) = Roof Area × Cooling Load (kWh/sq ft/yr) × (Reduction % / 100) var annualEnergySavedKwh = roofArea * coolingLoad * (reductionPct / 100);

// Annual energy cost savings ($) // Energy Cost Savings ($/yr) = Energy Saved (kWh/yr) × Electricity Rate ($/kWh) var annualEnergyCostSavings = annualEnergySavedKwh * energyRate;

// Total annual savings (energy + maintenance) var totalAnnualSavings = annualEnergyCostSavings + maintSavings;

// Simple Payback Period (years) // Payback (yrs) = Total Investment ($) / Total Annual Savings ($/yr) var simplePayback = totalInvestment / totalAnnualSavings;

// Total savings over coating lifespan (undiscounted) var totalSavingsUndiscounted = totalAnnualSavings * coatingLife;

// Net Present Value (NPV) of savings over lifespan // NPV = Σ [Annual Savings / (1 + r)^t] for t = 1 to N − Initial Investment // If r = 0, NPV = Total Savings − Investment var r = discountRate / 100; var pvSavings = 0; if (r === 0) { pvSavings = totalAnnualSavings * coatingLife; } else { // Present value of annuity: PV = PMT × [1 − (1+r)^−N] / r pvSavings = totalAnnualSavings * (1 - Math.pow(1 + r, -coatingLife)) / r; } var npv = pvSavings - totalInvestment;

// ROI over lifespan (%) // ROI (%) = (Total Net Savings / Total Investment) × 100 // = (Total Undiscounted Savings − Investment) / Investment × 100 var roiPct = ((totalSavingsUndiscounted - totalInvestment) / totalInvestment) * 100;

// Annualized ROI (%) // Annualized ROI = (1 + ROI/100)^(1/N) − 1 × 100 var annualizedRoi = (Math.pow(1 + roiPct / 100, 1 / coatingLife) - 1) * 100;

// CO₂ emissions avoided // Using US average grid emission factor: 0.386 kg CO₂/kWh (EPA eGRID 2022) var co2Factor = 0.386; // kg CO₂ per kWh var annualCo2Avoided = annualEnergySavedKwh * co2Factor; // kg/yr var lifetimeCo2Avoided = annualCo2Avoided * coatingLife; // kg

// ── Format helpers ───────────────────────────────────────────────────────── function fmt(n, dec) { return n.toLocaleString('en-US', {minimumFractionDigits: dec, maximumFractionDigits: dec}); } function fmtUSD(n) { return '$' + fmt(n, 2); } function fmtPct(n) { return fmt(n, 1) + '%'; }

var paybackStr = simplePayback = 0 ? 'calc-positive' : 'calc-negative'; var npvLabel = npv >= 0 ? 'Positive NPV — Financially Viable' : 'Negative NPV — Review Assumptions';

resultDiv.innerHTML = '### Results ' + '' + 'ParameterValue' + 'Total Upfront Investment' + fmtUSD(totalInvestment) + '' + 'Annual Energy Saved' + fmt(annualEnergySavedKwh, 0) + ' kWh/yr' + 'Annual Energy Cost Savings' + fmtUSD(annualEnergyCostSavings) + '/yr' + 'Annual Maintenance Savings' + fmtUSD(maintSavings) + '/yr' + 'Total Annual Savings' + fmtUSD(totalAnnualSavings) + '/yr' + 'Simple Payback Period' + paybackStr + '' + 'Total Savings over ' + coatingLife + ' yrs (undiscounted)' + fmtUSD(totalSavingsUndiscounted) + '' + 'Net Present Value (NPV)' + fmtUSD(npv) + ' — ' + npvLabel + '' + 'ROI over Coating Life' + fmtPct(roiPct) + '' + 'Annualized ROI' + fmtPct(annualizedRoi) + '/yr' + 'Annual CO₂ Avoided' + fmt(annualCo2Avoided / 1000, 2) + ' metric tons/yr' + 'Lifetime CO₂ Avoided' + fmt(lifetimeCo2Avoided / 1000, 2) + ' metric tons' + ''; }

#### Formulas Used

Total Investment ($) Total Investment = Roof Area (sq ft) × Coating Cost ($/sq ft)

Annual Energy Saved (kWh/yr) Energy Saved = Roof Area × Cooling Load (kWh/sq ft/yr) × (Reduction % ÷ 100)

Annual Energy Cost Savings ($/yr) Cost Savings = Energy Saved (kWh/yr) × Electricity Rate ($/kWh)

Total Annual Savings ($/yr) Total Annual Savings = Energy Cost Savings + Annual Maintenance Savings

Simple Payback Period (years) Payback = Total Investment ÷ Total Annual Savings

Net Present Value (NPV) NPV = [Annual Savings × (1 − (1 + r)−N) ÷ r] − Total Investment where r = discount rate (decimal), N = coating lifespan (years) If r = 0: NPV = (Annual Savings × N) − Total Investment

ROI over Coating Life (%) ROI = [(Total Undiscounted Savings − Total Investment) ÷ Total Investment] × 100

Annualized ROI (%) Annualized ROI = [(1 + ROI)1/N − 1] × 100

CO₂ Avoided (kg/yr) CO₂ Avoided = Energy Saved (kWh/yr) × 0.386 kg CO₂/kWh

#### Assumptions & References

More Calculators

References

Related Authorities

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