.solar-calculator-wrapper {
font-family: 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 0 auto;
color: #333;
line-height: 1.6;
}
.solar-calc-container {
background: #f9fbfd;
border: 1px solid #e1e8ed;
border-radius: 8px;
padding: 30px;
box-shadow: 0 4px 12px rgba(0,0,0,0.05);
margin-bottom: 40px;
}
.solar-calc-title {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
font-size: 24px;
font-weight: 700;
}
.solar-form-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
}
.solar-input-group {
margin-bottom: 15px;
}
.solar-input-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
font-size: 14px;
color: #4a5568;
}
.solar-input-group input, .solar-input-group select {
width: 100%;
padding: 12px;
border: 1px solid #cbd5e0;
border-radius: 6px;
font-size: 16px;
box-sizing: border-box;
transition: border-color 0.2s;
}
.solar-input-group input:focus {
border-color: #f6ad55;
outline: none;
}
.solar-btn {
background-color: #ed8936;
color: white;
border: none;
padding: 15px 30px;
font-size: 18px;
font-weight: bold;
border-radius: 6px;
cursor: pointer;
width: 100%;
margin-top: 10px;
transition: background-color 0.2s;
}
.solar-btn:hover {
background-color: #dd6b20;
}
.solar-results {
margin-top: 30px;
padding: 25px;
background-color: #fff;
border-left: 5px solid #ed8936;
border-radius: 4px;
display: none;
box-shadow: 0 2px 8px rgba(0,0,0,0.05);
}
.result-row {
display: flex;
justify-content: space-between;
margin-bottom: 12px;
padding-bottom: 12px;
border-bottom: 1px solid #edf2f7;
}
.result-row:last-child {
border-bottom: none;
margin-bottom: 0;
padding-bottom: 0;
}
.result-label {
font-weight: 600;
color: #718096;
}
.result-value {
font-weight: 700;
color: #2d3748;
font-size: 18px;
}
.highlight-value {
color: #276749;
font-size: 22px;
}
.error-msg {
color: #c53030;
text-align: center;
margin-top: 10px;
display: none;
font-weight: 600;
}
.solar-content {
margin-top: 50px;
}
.solar-content h2 {
color: #2d3748;
border-bottom: 2px solid #ed8936;
padding-bottom: 10px;
margin-top: 30px;
}
.solar-content h3 {
color: #4a5568;
margin-top: 25px;
}
.solar-content p {
margin-bottom: 15px;
color: #555;
}
.solar-content ul {
margin-bottom: 20px;
padding-left: 20px;
}
.solar-content li {
margin-bottom: 10px;
}
@media (max-width: 600px) {
.solar-form-grid {
grid-template-columns: 1fr;
}
}
function calculateSolarPayback() {
// Get Elements strictly by ID
var monthlyBillInput = document.getElementById('monthlyBill');
var costPerKwhInput = document.getElementById('costPerKwh');
var sunHoursInput = document.getElementById('sunHours');
var systemSizeInput = document.getElementById('systemSize');
var systemCostInput = document.getElementById('systemCost');
var taxCreditInput = document.getElementById('taxCredit');
var resultsDiv = document.getElementById('solarResults');
var errorDiv = document.getElementById('solarError');
// Parse values
var monthlyBill = parseFloat(monthlyBillInput.value);
var costPerKwh = parseFloat(costPerKwhInput.value);
var sunHours = parseFloat(sunHoursInput.value);
var systemSize = parseFloat(systemSizeInput.value);
var grossCost = parseFloat(systemCostInput.value);
var taxCreditPercent = parseFloat(taxCreditInput.value);
// Validation logic
if (isNaN(monthlyBill) || isNaN(costPerKwh) || isNaN(sunHours) ||
isNaN(systemSize) || isNaN(grossCost) || monthlyBill <= 0 || systemSize 0) {
paybackYears = netCost / annualSavings;
}
// 5. Calculate 25-Year Lifetime Savings
// Logic: (Annual Savings * 25) – Net Cost
// Advanced: Ideally accounts for energy price inflation and panel degradation, but we use linear for this specific calculator scope.
// Let's add a slight energy inflation factor of 2% per year for a more realistic SEO-friendly result
var lifetimeSavings = 0;
var currentAnnualSavings = annualSavings;
for (var i = 1; i 25) paybackText = '25+ Years';
document.getElementById('resPayback').innerText = paybackText;
document.getElementById('resLifetimeSavings').innerText = '$' + netLifetimeSavings.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 0});
// Show results
resultsDiv.style.display = 'block';
}
Solar Panel Payback & ROI Calculator
30% (Standard)
0%
10%
26%
Please enter valid positive numbers for all fields.
Net System Cost (After Tax Credit):
–
Estimated Annual Production:
–
Annual Savings (Year 1):
–
Break-Even Point:
–
25-Year Estimated Savings:
–
Understanding Your Solar Payback Period
Before investing in renewable energy, homeowners need to know one critical metric: the Solar Payback Period. This calculator helps you determine how long it will take for your solar panel system to "pay for itself" through electricity bill savings.
Key Factors Affecting Solar ROI
Your return on investment is influenced by several specific variables:
- System Size (kW): Larger systems generate more power but cost more upfront. Most residential systems range between 5kW and 10kW.
- Peak Sun Hours: This isn't just daylight hours; it's the number of hours per day the sun is intense enough to generate peak power. This varies significantly by geography (e.g., Arizona vs. Washington).
- Electricity Rates: The higher your local utility rates (Cost per kWh), the faster your solar system pays for itself because every kWh you generate is worth more.
- Federal Tax Credit: The Investment Tax Credit (ITC) currently allows you to deduct 30% of the cost of installing a solar energy system from your federal taxes, significantly lowering the "Net System Cost."
How to Read Your Results
Break-Even Point: This is the year when your cumulative energy savings equal the net cost of the system. A typical payback period in the US ranges from 6 to 10 years.
25-Year Estimated Savings: Solar panels are typically warrantied for 25 years. This figure estimates how much money you will save over the life of the system compared to sticking with your utility provider, factoring in a standard 2% annual increase in electricity prices.
Why System Efficiency Matters
This calculator applies a standard derating factor of 0.75. This accounts for real-world inefficiencies such as wiring loss, inverter conversion loss, shading, and dust. This ensures your estimated production numbers are realistic rather than theoretical maximums.