.solar-calc-header { background-color: #2e7d32; color: white; padding: 30px 20px; text-align: center; }
.solar-calc-header h1 { margin: 0; font-size: 28px; font-weight: 700; }
.solar-calc-container { padding: 30px; display: flex; flex-wrap: wrap; gap: 25px; }
.solar-calc-inputs { flex: 1; min-width: 300px; }
.solar-calc-results { flex: 1; min-width: 300px; background-color: #f9f9f9; padding: 25px; border-radius: 8px; border: 1px solid #eee; }
.input-group { margin-bottom: 20px; }
.input-group label { display: block; font-weight: 600; margin-bottom: 8px; font-size: 14px; color: #444; }
.input-group input { width: 100%; padding: 12px; border: 1px solid #ccc; border-radius: 4px; font-size: 16px; box-sizing: border-box; }
.input-group input:focus { border-color: #2e7d32; outline: none; box-shadow: 0 0 5px rgba(46, 125, 50, 0.2); }
.calc-btn { background-color: #2e7d32; color: white; border: none; padding: 15px 25px; font-size: 18px; font-weight: 700; border-radius: 4px; cursor: pointer; width: 100%; transition: background 0.3s; margin-top: 10px; }
.calc-btn:hover { background-color: #1b5e20; }
.result-item { display: flex; justify-content: space-between; padding: 12px 0; border-bottom: 1px solid #ddd; }
.result-item:last-child { border-bottom: none; }
.result-label { color: #666; font-size: 15px; }
.result-value { font-weight: 700; color: #2e7d32; font-size: 18px; }
.highlight-box { background-color: #e8f5e9; padding: 15px; border-radius: 6px; margin-bottom: 20px; text-align: center; border: 1px solid #c8e6c9; }
.highlight-box span { display: block; font-size: 24px; font-weight: 800; color: #2e7d32; }
.solar-article { padding: 30px; border-top: 1px solid #eee; background-color: #fff; }
.solar-article h2 { color: #2e7d32; font-size: 24px; margin-top: 0; }
.solar-article p { margin-bottom: 15px; color: #555; }
.solar-article ul { margin-bottom: 20px; padding-left: 20px; }
.solar-article li { margin-bottom: 8px; }
@media (max-width: 600px) { .solar-calc-container { flex-direction: column; } }
function calculateSolarROI() {
var systemCost = parseFloat(document.getElementById('systemCost').value);
var taxCredit = parseFloat(document.getElementById('taxCredit').value);
var annualProduction = parseFloat(document.getElementById('annualProduction').value);
var electricityRate = parseFloat(document.getElementById('electricityRate').value);
var annualIncrease = parseFloat(document.getElementById('annualIncrease').value) / 100;
if (isNaN(systemCost) || isNaN(annualProduction) || isNaN(electricityRate)) {
alert("Please enter valid numbers in all fields.");
return;
}
var netCost = systemCost – taxCredit;
var yearOneSavings = annualProduction * electricityRate;
var cumulativeSavings = 0;
var currentRate = electricityRate;
var currentProduction = annualProduction;
var paybackYear = 0;
var paybackFound = false;
for (var year = 1; year = netCost) {
// Linear interpolation for more accurate decimal year
var previousSavings = cumulativeSavings – yearlySavings;
var remainderNeeded = netCost – previousSavings;
paybackYear = (year – 1) + (remainderNeeded / yearlySavings);
paybackFound = true;
}
// Adjust for next year
currentRate = currentRate * (1 + annualIncrease);
currentProduction = currentProduction * 0.995; // 0.5% annual degradation
}
var totalROI = ((cumulativeSavings – netCost) / netCost) * 100;
// Update DOM
document.getElementById('netCostDisplay').innerText = '$' + netCost.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 0});
document.getElementById('yearOneSavings').innerText = '$' + yearOneSavings.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 0});
document.getElementById('totalSavings').innerText = '$' + cumulativeSavings.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 0});
document.getElementById('roiPercentage').innerText = totalROI.toFixed(0) + '%';
if (paybackFound) {
document.getElementById('paybackYears').innerText = paybackYear.toFixed(1) + ' Years';
} else {
document.getElementById('paybackYears').innerText = '25+ Years';
}
}
// Run once on load
window.onload = function() {
calculateSolarROI();
};
Solar Panel ROI Calculator
Estimate your savings and payback period for a home solar installation
Estimated Payback Period
8.2 Years
Net System Cost:
$17,500
Year 1 Savings:
$1,760
25-Year Total Savings:
$64,168
Total ROI Percentage:
266%
Understanding Your Solar Return on Investment
Switching to solar energy is one of the most significant financial investments a homeowner can make. Beyond the environmental benefits, the "Return on Investment" (ROI) measures how much money you save compared to what you spend on the system.
How the ROI is Calculated
To determine your solar payback period and long-term ROI, we analyze several key factors:
- Net System Cost: This is the gross price of the solar panels and installation minus the Federal Solar Tax Credit (ITC) and any local utility rebates.
- Annual Energy Production: The amount of electricity your panels generate annually depends on your roof's orientation, local sunlight hours, and panel efficiency.
- Utility Rate Inflation: Historically, electricity rates rise by 2-4% annually. Your savings increase every year as utility power becomes more expensive.
- System Degradation: Most solar panels lose about 0.5% efficiency per year, which we factor into long-term savings.
Example Calculation
Imagine a homeowner in California installs a system for $20,000. After a 30% federal tax credit, the net cost is $14,000. If the system generates $2,000 worth of electricity in the first year, the payback period is roughly 7 years. Over 25 years (the typical warranty life of panels), that system could save the homeowner over $50,000 in avoided utility costs.
Factors That Can Improve Your ROI
Your actual ROI may be even higher if you live in a state with Net Metering, which allows you to sell excess energy back to the grid at retail rates. Additionally, some states offer SRECs (Solar Renewable Energy Certificates), which provide cash payments based on the energy your system produces.