.solar-calc-container {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 20px auto;
padding: 25px;
border: 1px solid #e0e0e0;
border-radius: 12px;
background-color: #f9fbfd;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.solar-calc-container h2 {
color: #2c3e50;
text-align: center;
margin-bottom: 25px;
}
.solar-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
}
.solar-input-group {
margin-bottom: 15px;
}
.solar-input-group label {
display: block;
font-weight: 600;
margin-bottom: 8px;
color: #34495e;
font-size: 14px;
}
.solar-input-group input {
width: 100%;
padding: 12px;
border: 1px solid #ccc;
border-radius: 6px;
box-sizing: border-box;
font-size: 16px;
}
.solar-calc-btn {
grid-column: span 2;
background-color: #27ae60;
color: white;
border: none;
padding: 15px;
border-radius: 6px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
transition: background-color 0.3s;
margin-top: 10px;
}
.solar-calc-btn:hover {
background-color: #219150;
}
#solar-results {
margin-top: 25px;
padding: 20px;
background-color: #ffffff;
border-radius: 8px;
display: none;
border-left: 5px solid #27ae60;
}
.result-item {
display: flex;
justify-content: space-between;
padding: 10px 0;
border-bottom: 1px solid #eee;
}
.result-item:last-child {
border-bottom: none;
}
.result-label {
color: #7f8c8d;
font-weight: 500;
}
.result-value {
color: #2c3e50;
font-weight: 700;
font-size: 1.1em;
}
.highlight-value {
color: #27ae60;
}
@media (max-width: 600px) {
.solar-grid { grid-template-columns: 1fr; }
.solar-calc-btn { grid-column: 1; }
}
Solar Panel ROI Calculator
System Size (kW)
Total System Cost ($)
Tax Credit Percentage (%)
Electricity Rate ($/kWh)
Avg. Peak Sun Hours/Day
Utility Price Increase (%/yr)
Calculate My Savings
Net System Cost (after credits):
$0.00
Estimated Annual Production:
0 kWh
First Year Savings:
$0.00
Solar Payback Period:
0 Years
25-Year Net Profit:
$0.00
Understanding Solar Panel ROI: Is Solar Worth It?
Switching to solar energy is a significant financial decision. Understanding your Return on Investment (ROI) involves more than just looking at your monthly bill reduction; it requires analyzing the upfront costs, government incentives, and the long-term appreciation of energy prices.
Key Factors Influencing Solar ROI
The Federal Solar Tax Credit (ITC): Currently, the residential clean energy credit allows you to deduct 30% of your solar installation costs from your federal taxes. This significantly lowers the "Net Cost."Peak Sun Hours: This isn't just daylight. It refers to the intensity of sunlight. Areas like Arizona might average 6 hours, while the Pacific Northwest might average 3.5.Electricity Rates: The more you pay your utility company per kilowatt-hour (kWh), the more money you save by producing your own power.System Degradation: Most solar panels are warrantied for 25 years. They typically lose about 0.5% efficiency each year, which is accounted for in long-term ROI projections.
How to Calculate Your Payback Period
To find your payback period manually, you divide your Net System Cost by your Annual Energy Savings . For example, if a system costs $14,000 after credits and saves you $2,000 a year in electricity, your payback period is 7 years. After those 7 years, the electricity generated is essentially free for the remaining life of the system.
Example ROI Scenario
Imagine a typical 8kW system in a region with 4.5 peak sun hours.
Gross Cost: $24,00030% Tax Credit: -$7,200Net Cost: $16,800Annual Production: 8kW * 4.5 hours * 365 days * 0.78 (derate factor) = ~10,249 kWh/year.Annual Savings: 10,249 kWh * $0.15/kWh = $1,537.Payback Period: $16,800 / $1,537 = ~10.9 Years .
function calculateSolarROI() {
// Get Inputs
var systemSize = parseFloat(document.getElementById("systemSize").value);
var totalCost = parseFloat(document.getElementById("totalCost").value);
var taxCreditPct = parseFloat(document.getElementById("taxCredit").value);
var rate = parseFloat(document.getElementById("electricityRate").value);
var sunHours = parseFloat(document.getElementById("sunHours").value);
var annualIncrease = parseFloat(document.getElementById("annualIncrease").value) / 100;
// Validation
if (isNaN(systemSize) || isNaN(totalCost) || isNaN(rate) || isNaN(sunHours)) {
alert("Please enter valid numerical values.");
return;
}
// 1. Calculate Net Cost
var netCost = totalCost * (1 – (taxCreditPct / 100));
// 2. Calculate Annual Production
// Standard derate factor for inverter loss, wiring, and soil is ~0.78
var annualProduction = systemSize * sunHours * 365 * 0.78;
// 3. Calculate Savings and Payback
var yearOneSavings = annualProduction * rate;
// Cumulative Calculation for Payback and 25-Year Profit
var cumulativeSavings = 0;
var paybackYear = 0;
var currentRate = rate;
var total25YearSavings = 0;
var foundPayback = false;
for (var year = 1; year = netCost && !foundPayback) {
paybackYear = year – 1 + ((netCost – (cumulativeSavings – yearlySaving)) / yearlySaving);
foundPayback = true;
}
currentRate = currentRate * (1 + annualIncrease);
}
var net25YearProfit = total25YearSavings – netCost;
// Display Results
document.getElementById("solar-results").style.display = "block";
document.getElementById("netCostDisplay").innerText = "$" + netCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("annualProductionDisplay").innerText = Math.round(annualProduction).toLocaleString() + " kWh";
document.getElementById("yearOneSavingsDisplay").innerText = "$" + yearOneSavings.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
if (foundPayback) {
document.getElementById("paybackPeriodDisplay").innerText = paybackYear.toFixed(1) + " Years";
} else {
document.getElementById("paybackPeriodDisplay").innerText = "Over 25 Years";
}
document.getElementById("totalProfitDisplay").innerText = "$" + net25YearProfit.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
// Scroll to results
document.getElementById("solar-results").scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}