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Solar Panel ROI Calculator

Payback Period —
Annual Savings —
25-Year Net Profit —

Understanding Your Solar Investment Return (ROI)

Switching to solar energy is one of the most effective ways to hedge against rising utility costs. To accurately determine your Return on Investment (ROI), you must look beyond the initial installation price and consider the long-term energy production of the panels.

Key Variables in Solar Math

  • System Size: Usually measured in kilowatts (kW). An average residential system ranges from 5kW to 10kW.
  • Peak Sun Hours: This isn't the total daylight, but the intensity of sun. For example, California averages 5-6 hours, while the Northeast may average 4.
  • The Federal ITC: The Investment Tax Credit currently allows you to deduct 30% of your solar installation costs from your federal taxes.
  • Degradation Rate: Most panels lose about 0.5% efficiency per year, which we factor into our 25-year profit calculation.

Example ROI Scenario

If you install a 6kW system at $18,000 in an area with 4.5 sun hours and a $0.15/kWh rate:
1. Net Cost after 30% Tax Credit: $12,600.
2. Annual Energy Production: ~8,376 kWh.
3. Annual Savings: ~$1,256.
4. Payback Period: Approximately 10 years.

function calculateSolarROI() { var size = parseFloat(document.getElementById('solarSize').value); var cost = parseFloat(document.getElementById('totalCost').value); var rate = parseFloat(document.getElementById('elecRate').value); var hours = parseFloat(document.getElementById('sunHours').value); var useITC = document.getElementById('applyITC').checked; if (isNaN(size) || isNaN(cost) || isNaN(rate) || isNaN(hours)) { alert("Please enter valid numeric values."); return; } // Apply Federal Tax Credit var netCost = useITC ? (cost * 0.7) : cost; // Annual Production: Size(kW) * SunHours * 365 days * 0.85 (system efficiency loss) var annualKwh = size * hours * 365 * 0.85; // Annual Savings var annualSavings = annualKwh * rate; // Payback Period (Years) var payback = netCost / annualSavings; // 25-Year ROI Calculation (including 0.5% annual degradation) var totalSavings25 = 0; for (var i = 0; i < 25; i++) { totalSavings25 += (annualSavings * Math.pow(0.995, i)); } var netProfit = totalSavings25 – netCost; // Update UI document.getElementById('solar-results').style.display = 'block'; document.getElementById('resPayback').innerText = payback.toFixed(1) + " Years"; document.getElementById('resAnnual').innerText = "$" + annualSavings.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('resTotal').innerText = "$" + netProfit.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); }

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