function calculateSolarROI() {
var systemCost = parseFloat(document.getElementById('systemCost').value);
var taxCredit = parseFloat(document.getElementById('taxCredit').value);
var monthlyBill = parseFloat(document.getElementById('monthlyBill').value);
var energyOffset = parseFloat(document.getElementById('energyOffset').value) / 100;
var utilityIncrease = parseFloat(document.getElementById('utilityIncrease').value) / 100;
if (isNaN(systemCost) || isNaN(taxCredit) || isNaN(monthlyBill)) {
alert("Please enter valid numerical values.");
return;
}
var netCost = systemCost * (1 – (taxCredit / 100));
var annualSavingsYear1 = (monthlyBill * 12) * energyOffset;
// Calculate Payback and 25-year cumulative savings with inflation
var cumulativeSavings = 0;
var currentYearSavings = annualSavingsYear1;
var paybackYears = 0;
var foundPayback = false;
for (var i = 1; i = netCost) {
paybackYears = i – 1 + ((netCost – (cumulativeSavings – currentYearSavings)) / currentYearSavings);
foundPayback = true;
}
currentYearSavings *= (1 + utilityIncrease);
}
var totalROI = ((cumulativeSavings – netCost) / netCost) * 100;
document.getElementById('netCostDisplay').innerText = "$" + netCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('paybackDisplay').innerText = paybackYears.toFixed(1) + " Years";
document.getElementById('totalSavingsDisplay').innerText = "$" + cumulativeSavings.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('roiDisplay').innerText = totalROI.toFixed(1) + "%";
document.getElementById('resultsArea').style.display = 'block';
}
Understanding Your Solar Investment
Switching to solar energy is more than just an environmental choice; it is a significant financial strategy for long-term wealth. This Solar ROI Calculator helps you visualize how the initial cost of installation is offset by monthly utility savings and government incentives.
Key Factors in Solar ROI
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.
Utility Inflation: Electricity rates typically rise by 3-5% annually. Solar locks in your energy costs, making your savings grow as utility prices climb.
Energy Offset: This is the percentage of your home's electricity needs that the solar panels provide. A 100% offset means you produce as much energy as you consume.
Realistic Example
If a homeowner spends $25,000 on a solar system and qualifies for the 30% Federal Tax Credit, their net cost drops to $17,500. If their previous electric bill was $150/month and they offset 100% of their usage, they save $1,800 in the first year. With a 4% annual utility rate increase, the system typically pays for itself in 8 to 9 years, providing pure profit for the remainder of the system's 25-year lifespan.
Frequently Asked Questions
Is solar a good investment if I move in 5 years?
While the full ROI takes longer, studies show that solar panels increase home property values by an average of 4.1%, often recouping the initial investment upon sale.
Does the calculator include maintenance?
Solar panels are low-maintenance with no moving parts. Most systems require only periodic cleaning and include 25-year warranties, making maintenance costs negligible in ROI calculations.