Estimate your payback period and 20-year savings from switching to solar energy.
Net System Cost (After Credits):–
Estimated Annual Savings (Year 1):–
Break-Even Payback Period:–
Total 20-Year Savings (Projected):–
Understanding Your Solar Investment
Switching to renewable energy is not just an environmental decision; it is a significant financial investment. Our Solar Panel Savings Calculator helps homeowners determine the financial viability of installing a photovoltaic (PV) system by analyzing the relationship between upfront costs, tax incentives, and long-term energy savings.
How the Solar Payback Period is Calculated
The "payback period" is the time it takes for your cumulative energy savings to equal the net cost of the solar panel system. The formula used in this calculator considers:
Gross System Cost: The total price quoted by your installer before incentives.
Tax Incentives: Specifically the Federal Solar Investment Tax Credit (ITC), which currently offers a 30% credit for systems installed in the US.
Energy Inflation: Electricity rates historically rise over time. This calculator assumes your savings grow annually based on the inflation rate entered (typically 2-3%).
Why Net Cost Matters
The "sticker price" of solar is rarely what you actually pay. By subtracting the 30% Federal Tax Credit (and any applicable state rebates), your Net System Cost is significantly lower. For example, a $20,000 system effectively costs $14,000 after the 30% credit is applied.
Maximizing Your Solar ROI
To ensure the shortest payback period and highest 20-year savings, consider the following:
System Sizing: Ensure your system is sized to offset 100% of your average monthly bill without excessive overproduction unless your utility offers full net metering.
Sun Exposure: South-facing roofs with minimal shade generate the most power per dollar invested.
Local Rates: Homeowners in areas with high electricity rates (like California or the Northeast) see much faster ROI than those in areas with cheap power.
function calculateSolarROI() {
// 1. Get Input Values
var monthlyBill = parseFloat(document.getElementById('monthlyBill').value);
var systemCost = parseFloat(document.getElementById('systemCost').value);
var taxCredit = parseFloat(document.getElementById('taxCredit').value);
var inflationRate = parseFloat(document.getElementById('energyInflation').value);
// 2. Input Validation
if (isNaN(monthlyBill) || monthlyBill <= 0) {
alert("Please enter a valid monthly electric bill.");
return;
}
if (isNaN(systemCost) || systemCost <= 0) {
alert("Please enter a valid system cost.");
return;
}
if (isNaN(taxCredit) || taxCredit < 0) {
taxCredit = 0;
}
if (isNaN(inflationRate) || inflationRate < 0) {
inflationRate = 0;
}
// 3. Logic Calculation
// Calculate Net Cost
var creditAmount = systemCost * (taxCredit / 100);
var netCost = systemCost – creditAmount;
// Calculate Year 1 Annual Savings
var annualSavingsYear1 = monthlyBill * 12;
// Calculate Payback Period and 20 Year Savings using inflation loop
var cumulativeSavings = 0;
var paybackYears = 0;
var foundPayback = false;
var totalSavings20Years = 0;
var currentAnnualSavings = annualSavingsYear1;
for (var year = 1; year = netCost) {
// Calculate fractional year for more precision
var previousCumulative = cumulativeSavings – currentAnnualSavings;
var remainingCost = netCost – previousCumulative;
var fraction = remainingCost / currentAnnualSavings;
paybackYears = (year – 1) + fraction;
foundPayback = true;
}
// Compound savings for next year based on inflation
currentAnnualSavings = currentAnnualSavings * (1 + (inflationRate / 100));
}
// Calculate Total Net Savings (Total saved – Initial Net Cost)
var totalNetSavings = cumulativeSavings – netCost;
// 4. Formatting and Display
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 0,
maximumFractionDigits: 0,
});
document.getElementById('resNetCost').innerText = formatter.format(netCost);
document.getElementById('resAnnualSavings').innerText = formatter.format(annualSavingsYear1);
if (foundPayback) {
document.getElementById('resPayback').innerText = paybackYears.toFixed(1) + " Years";
} else {
document.getElementById('resPayback').innerText = "20+ Years";
}
document.getElementById('resTotalSavings').innerText = formatter.format(totalNetSavings);
// Show results
document.getElementById('results').style.display = 'block';
}