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Solar ROI & Payback Calculator

Estimate your savings and return on investment for a home solar power system.

Net System Cost (after tax credit): $0.00
Estimated Monthly Production: 0 kWh
Estimated Monthly Savings: $0.00
Payback Period (Break-Even): 0.0 Years
25-Year Total Savings: $0.00

Understanding Your Solar Return on Investment (ROI)

Switching to solar energy is one of the most significant financial and environmental decisions a homeowner can make. This Solar ROI Calculator helps you break down the complex variables into simple metrics: how much it costs, how much you save, and when the system pays for itself.

How the Solar Payback Period is Calculated

The solar payback period represents the time it takes for the cumulative electricity bill savings to equal the initial net cost of the system. We use the following formula:

  • Net Cost: Total Installation Cost – (Total Installation Cost * Federal Investment Tax Credit percentage).
  • Annual Savings: (System Size in kW * Peak Sun Hours * 365 days) * Electricity Rate.
  • Payback Period: Net Cost / Annual Savings.

Key Factors Influencing Your Results

1. Peak Sun Hours: This isn't just daylight; it's the intensity of sunlight. Areas like Arizona might have 6.0 hours, while the Pacific Northwest might have 3.5 hours. Higher sun hours mean faster ROI.

2. Electricity Rates: The more you pay your utility company per kilowatt-hour (kWh), the more valuable every solar electron becomes. High-rate states like California or Massachusetts often see much faster payback periods.

3. Federal and Local Incentives: The Federal Investment Tax Credit (ITC) currently allows you to deduct 30% of your solar installation costs from your federal taxes. This significantly lowers the "Net Cost."

Realistic Solar ROI Example

Imagine a homeowner in Florida installing a 7kW system for $21,000. With the 30% federal tax credit, the net cost drops to $14,700. If the system produces 900 kWh per month in a region with $0.15/kWh rates, the monthly savings are $135. The payback period would be roughly 9 years, leaving 16+ years of "free" electricity over the life of the panels.

function calculateSolarROI() { var bill = parseFloat(document.getElementById("monthlyBill").value); var rate = parseFloat(document.getElementById("elecRate").value); var size = parseFloat(document.getElementById("systemSize").value); var cost = parseFloat(document.getElementById("totalCost").value); var sun = parseFloat(document.getElementById("sunHours").value); var credit = parseFloat(document.getElementById("taxCredit").value); if (isNaN(bill) || isNaN(rate) || isNaN(size) || isNaN(cost) || isNaN(sun) || isNaN(credit)) { alert("Please enter valid numbers in all fields."); return; } // 1. Calculate Net Cost var taxCreditAmount = cost * (credit / 100); var netCost = cost – taxCreditAmount; // 2. Calculate Production // System Size (kW) * Sun Hours * Days in Month var monthlyProd = size * sun * 30.4; // 3. Calculate Savings // Value of electricity produced var monthlySavingsValue = monthlyProd * rate; // We cap monthly savings at the actual bill unless net metering allows profit // Most residential setups aim to offset the bill. var actualMonthlySavings = monthlySavingsValue; if (actualMonthlySavings > bill) { // If they produce more than they use, value it slightly lower or cap at bill // For ROI we'll assume they offset the full bill but give credit for overproduction actualMonthlySavings = monthlySavingsValue; } var annualSavings = actualMonthlySavings * 12; // 4. Payback Period var paybackYears = netCost / annualSavings; // 5. 25-Year Savings (Industry Standard Warranty period) // Factoring in 0.5% degradation per year (simple linear) var total25YearSavings = 0; for (var i = 0; i < 25; i++) { total25YearSavings += annualSavings * Math.pow(0.995, i); } var net25YearProfit = total25YearSavings – netCost; // Display Results document.getElementById("solarResults").style.display = "block"; document.getElementById("netCostDisplay").innerHTML = "$" + netCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById("monthlyProdDisplay").innerHTML = Math.round(monthlyProd) + " kWh"; document.getElementById("monthlySavingsDisplay").innerHTML = "$" + actualMonthlySavings.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById("paybackDisplay").innerHTML = paybackYears.toFixed(1) + " Years"; document.getElementById("totalSavingsDisplay").innerHTML = "$" + net25YearProfit.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); // Scroll to results on mobile document.getElementById("solarResults").scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }

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