Estimate your monthly savings and payback period based on your local sunlight and energy costs.
Daily Energy Production:0 kWh
Estimated Monthly Savings:$0.00
Estimated Annual Savings:$0.00
Payback Period (ROI):0 Years
How to Use the Solar Savings Calculator
Calculating the return on investment (ROI) for solar panels involves understanding how much energy your specific setup generates versus what you currently pay your utility company. To use this tool effectively, follow these steps:
System Size: Most residential systems range from 3kW to 10kW. If you haven't received a quote yet, 5kW is a standard starting point for a medium-sized home.
Peak Sun Hours: This isn't just daylight hours; it's the intensity of the sun. In the US, this typically ranges from 3.5 hours (North) to 6 hours (Southwest).
Electricity Rate: Check your recent utility bill for the "Price per kWh." The national average is approximately $0.15 to $0.20.
Net Installation Cost: This is the total price after applying the 30% Federal Solar Tax Credit (ITC) and any local rebates.
Understanding Solar Efficiency and ROI
Our calculator applies a standard 75% efficiency derate factor. This accounts for real-world variables like inverter loss, wiring resistance, and panel soiling (dust). Even the best panels don't convert 100% of sunlight into usable AC electricity for your home.
The "Payback Period" is the most critical metric for homeowners. It tells you exactly how many years it will take for the utility bill savings to cover the initial cost of the system. Most modern solar installations pay for themselves within 6 to 10 years, while the panels themselves are warranted to last 25 years.
Example Calculation
If you install a 6kW system in a region with 5 peak sun hours and pay $0.18 per kWh, your system produces roughly 22.5 kWh per day (after efficiency losses). This leads to approximately $121 in monthly savings. If the system cost $13,000 after incentives, your payback period would be roughly 8.9 years.
function calculateSolarSavings() {
var size = parseFloat(document.getElementById("systemSize").value);
var sun = parseFloat(document.getElementById("sunHours").value);
var rate = parseFloat(document.getElementById("elecRate").value);
var cost = parseFloat(document.getElementById("installCost").value);
var resultsDiv = document.getElementById("solarResults");
if (isNaN(size) || isNaN(sun) || isNaN(rate) || isNaN(cost) || size <= 0 || sun <= 0 || rate <= 0 || cost <= 0) {
alert("Please enter valid positive numbers for all fields.");
return;
}
// Standard solar efficiency factor (0.75 – 0.80)
var efficiency = 0.75;
// Daily Production: kW * hours * efficiency
var dailyKwh = size * sun * efficiency;
// Monthly Savings: Daily kWh * 30 days * Rate
var monthlySavings = dailyKwh * 30.42 * rate;
// Annual Savings
var annualSavings = monthlySavings * 12;
// Payback Period: Total Cost / Annual Savings
var years = cost / annualSavings;
// Display Results
document.getElementById("dailyProd").innerText = dailyKwh.toFixed(2) + " kWh";
document.getElementById("monthlySave").innerText = "$" + monthlySavings.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("annualSave").innerText = "$" + annualSavings.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("paybackPeriod").innerText = years.toFixed(1) + " Years";
resultsDiv.style.display = "block";
resultsDiv.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}