Estimate your potential savings and break-even point for a residential solar system.
Net Installation Cost (After Credit):$0.00
Estimated Annual Production:0 kWh
Estimated Annual Savings:$0.00
Payback Period (Break-Even):0 Years
25-Year Total Savings:$0.00
Understanding Your Solar Return on Investment
Switching to solar power is one of the most significant financial and environmental decisions a homeowner can make. This calculator helps you navigate the "Solar Payback Period"—the amount of time it takes for your electricity savings to equal the initial cost of the system.
How the Calculation Works
To determine your ROI, we analyze several key factors:
Net Cost: We take your gross installation price and subtract the Federal Investment Tax Credit (ITC), which is currently 30% in the United States.
Annual Energy Production: Calculated by multiplying your system size (kW) by your regional peak sun hours per day, adjusted for a standard 75% system efficiency factor.
Annual Savings: This is the total kWh produced multiplied by your local utility's rate per kWh.
Typical Solar Payback Factors
Most residential solar systems in the US have a payback period between 6 to 10 years. However, this varies based on:
Local Utility Rates: The higher your current electric bill, the faster your system pays for itself.
Sunlight Exposure: Homes in Arizona or California will produce more energy with the same size system than homes in Washington or Maine.
Incentives: State-level rebates or SREC (Solar Renewable Energy Certificate) programs can shave years off your break-even point.
Example Calculation
If you spend $20,000 on a 7kW system and receive a $6,000 tax credit, your net cost is $14,000. If that system saves you $2,000 per year in electricity, your payback period is exactly 7 years. Since most panels are warrantied for 25 years, you would enjoy 18 years of virtually free electricity.
function calculateSolarROI() {
// Get Input Values
var monthlyBill = parseFloat(document.getElementById('monthlyBill').value);
var rate = parseFloat(document.getElementById('electricityRate').value);
var size = parseFloat(document.getElementById('systemSize').value);
var cost = parseFloat(document.getElementById('installCost').value);
var sun = parseFloat(document.getElementById('sunHours').value);
var tax = parseFloat(document.getElementById('taxCredit').value);
// Validate inputs
if (isNaN(monthlyBill) || isNaN(rate) || isNaN(size) || isNaN(cost) || isNaN(sun)) {
alert("Please enter valid numbers in all fields.");
return;
}
// Logic: Net Cost
var taxCreditAmount = cost * (tax / 100);
var netCost = cost – taxCreditAmount;
// Logic: Annual Production (0.75 is standard system derate factor for losses)
var annualKwh = size * sun * 365 * 0.75;
// Logic: Annual Savings
var annualSavings = annualKwh * rate;
// Logic: Payback Period
var paybackYears = netCost / annualSavings;
// Logic: 25 Year Lifetime Savings (assuming 2% energy cost inflation)
var lifetimeSavings = 0;
var currentYearSavings = annualSavings;
for (var i = 1; i <= 25; i++) {
lifetimeSavings += currentYearSavings;
currentYearSavings *= 1.02; // 2% annual inflation of utility prices
}
var totalProfit = lifetimeSavings – netCost;
// Display Results
document.getElementById('solar-results').style.display = 'block';
document.getElementById('netCostDisplay').innerText = '$' + netCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('annualProdDisplay').innerText = Math.round(annualKwh).toLocaleString() + ' kWh';
document.getElementById('annualSavingsDisplay').innerText = '$' + annualSavings.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('paybackDisplay').innerText = paybackYears.toFixed(1) + ' Years';
document.getElementById('lifetimeSavingsDisplay').innerText = '$' + totalProfit.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
}